Title & Abstract

1.

Name of the speaker: Prof. Howard Wiseman, Griffith University, Australia

Title: CAN A QUBIT BE YOUR FRIEND?

Why experimental metaphysics needs a quantum computer

Abstract: Experimental metaphysics is the study of how empirical results can reveal indisputable facts about the fundamental nature of the world, independent of any theory. It is a field born from Bell’s 1964 theorem, and the experiments it inspired, proving the world cannot be both local and deterministic. However, there is an implicit assumption in Bell’s theorem, that the observed result of any measurement is absolute (it has some value which is not ‘relative to its observer’). This assumption may be called into question when the observer becomes a quantum system (the “Wigner’s Friend” scenario), which has recently been the subject of renewed interest. Here, building on work by Brukner, we derive a theorem, in experimental metaphysics, for this scenario [1]. It is similar to Bell’s 1964 theorem but dispenses with the assumption of determinism. The remaining assumptions, which we collectively call "local friendliness", yield a strictly larger polytope of bipartite correlations than those in Bell's theorem (local determinism), but quantum mechanics still allows correlations outside the local friendliness polytope. We illustrate this in an experiment in which the friend system is a single photonic qubit [1]. I argue that a truly convincing experiment could be realised if that system were a sufficiently advanced artificial intelligence software running on a very large quantum computer, so that it could be regarded genuinely as a friend. I will briefly discuss the implications of this far-future scenario for various interpretations and modifications of quantum theory.

[1] Kok-Wei Bong, Aníbal Utreras-Alarcón, Farzad Ghafari, Yeong-Cherng Liang, Nora Tischler, Eric G. Cavalcanti, Geoff J. Pryde and Howard M. Wiseman, “A strong no-go theorem on the Wigner’s friend paradox", Nature Physics (2020).

2.

Name of the speaker: Prof. Fabrizio Piacentini, INRiM, Italy

Title: Weak-interaction-based measurements: a new tool for quantum technologies

Abstract: Measurements can be considered one of the pillars of physics, especially in Quantum Mechanics, because of features without classical counterparts like the wave function collapse in "sharp" (projective) measurements.

In the last decades, among the most interesting measurement paradigms discussed and tested in the quantum physics community, one can find weak measurements. i.e. measurements characterized by an interaction weak enough to avoid the wave function collapse, representing an excellent tool for both fundamental research and quantum technologies.

Furthermore, in recent years new measurement paradigms have been proposed as a further evolution of weak measurements, e.g. protective measurements, able to obtain information on the expectation value of an observable even measuring a single particle. A second example is given by genetic quantum measurements, showing analogies with the typical evolution-inspired mechanisms of genetic algorithms and yielding uncertainties even below the quantum Cramér-Rao bound, while a third one is represented by robust weak measurements, able to reliably extract a weak value (even an anomalous one) with just a single click of the detector, without the usual average on multiple detection events.

In this talk, after a general introduction, I will present some of the latest results related to the experimental implementation of weak-interaction-based measurement protocols in different scenarios, highlighting their new, disruptive features and advantages related to both the quantum foundations and quantum technologies frameworks.

3.

Name of the Speaker: Prof. G S Agarwal*, Texas A & M University

Title: Two-Photon Processes in Entangled Fields

Abstract: Two photon processes like nonlinear absorption and Raman scattering are known to provide wealth of information on systems of interest. These are typically studied by using coherent laser fields. The efficiency of such processes depends on the interference among different path ways from initial state to final state. The use of entangled light and more generally quantum light can be used to control these path ways and to enhance the efficiency of the two photon and more generally multiphoton and nonlinear coherent processes like up-conversion, leading to new directions of research in nonlinear spectroscopy. I would describe the fundamentals and recent progress in the study of two photon processes in Entangled fields.

*girish.agarwal@tamu.edu

4.

Name of the Speaker: Prof. Lev vaidman, Tel Aviv University, Israel

Title: Experimental demonstrations of exotic quantum measurements

Abstract: I will report first demonstrations of various types of quantum measurements. Nonlocal measurement - measurement of a property of a composite quantum system with spatially separated parts. Protective measurement - measuring expectation value of an observable with a single click. Robust weak measurement - measuring weak value of an observable with a single click. Modified interaction-free measurement: measurement that tells us that the place is empty without any particle passing through it.

5.

Name of the Speaker: Prof. Franco Nori, (RIKEN, Japan, and University of Michigan, Ann Arbor, USA)

Title: A few examples of Machine Learning and Artificial Neural Networks applied to Quantum Physics

Abstract: Machine learning provides effective methods for identifying topological features [1]. We show that unsupervised manifold learning can successfully retrieve topological quantum phase transitions [1]. We have also developed [2] machine learning-inspired quantum state tomography based on neural-network representations of quantum states. We also consider conditional generative adversarial networks (CGANs) to QST [3]. We demonstrate [4] that artificial neural networks can simulate first-principles calculations of extended materials.

[1] Y. Che, C. Gneiting, T. Liu, F. Nori, Topological Quantum Phase Transitions Retrieved from Manifold Learning, Phys. Rev. B 102, 134213 (2020).

[2] A. Melkani, C. Gneiting, F. Nori, Eigenstate extraction with neural-network tomography, Phys. Rev. A 102, 022412 (2020).

[3] S. Ahmed, C.S. Munoz, F. Nori, A.F. Kockum, Quantum State Tomography with Conditional Generative Adversarial Networks, (2020). [arXiv]

[4] N. Yoshioka, W. Mizukami, F. Nori, Neural-Network Quantum States for the Electronic Structure of Real Solids, Communications Physics, 4, 106 (2021).

[5] K. Bartkiewicz, et al., Experimental kernel-based quantum machine learning in finite feature space, Sci. Rep. 10, 12356 (2020).

PDF files of these publications can be found here: https://dml.riken.jp/pub/ai_meets_qp/

All of our work is accessible here: https://dml.riken.jp/pub/

*Our work is supported in part by NTT Research, JST, JSPS, ARO, AFOSR, AOARD, and FQXi.

6.

Name of the Speaker: Prof. Michael Hall, Australian National University

Title: How to cheat at quantum cryptography: the roles of free will, causality and retrocausality

Abstract: The promise of strong quantum cryptography relies on assumptions of locality and free choice. If these assumptions hold, and if the measurement correlations between the coding devices satisfy a so-called Bell inequality, then it is impossible for an external eavesdropper to have knowledge of the code generated by the devices. I will discuss how the free choice assumption may be violated in practice, while maintaining locality, and some implications thereof. The minimal information resources that allow perfect eavesdropping is determined to be a mere 0.08 bits of causal correlation, between the physical source and the "random number generators" (possibly humans) that determine the measurement settings. Devices can be built that exploit this possibility, leading to a buyer-beware warning for off-the-shelf quantum cryptography apparatus. Further, and somewhat surprisingly, only ~0.04 bits are required if retrocausal correlations are permitted. While we cannot build devices that exploit the latter possibility, its greater efficiency provides an interesting "Occam's razor" argument for retrocausality in nature.

Further information:

7.

Name of the Speaker: Prof. Valerio Scarani, National University of Singapore

Title: optimal discrimination of optical modes

Abstract: This talk shall start with the classic Helstrom discrimination of two states. I shall then explain how discrimination among more states can be approached using semi-definite programs (SDP). With these tools, I shall introduce the notion of discrimination of optical modes. I shall describe how the SDP approach can be generalised to deal with this case, and show a couple of interesting examples [from: I.W. Primaatmaja, A. Ho, VS, Phys. Rev. A 103, 052410 (2021); https://arxiv.org/abs/2012.11104].

8.

Name of the speaker: Prof. Alexandre MATZKIN, CNRS, France

Title: Wigner-Friend scenarios: from the Measurement problem to the consistency of Quantum Mechanics

Abstract: The measurement problem still hovers over the foundations of quantum theory. While in most situations we do not need to bother (at least for practical purposes) about these conceptual difficulties, in some instances the role of the Observer and the nature of the quantum state become prominent. This is the case for Wigner-Friend scenarios, which involve observers that measure other observers measuring a quantum system. Here different ways of understanding the measurement axioms lead to different predictions for the outcomes of (what are at least for now) thought-experiments. In this talk, I will discuss these issues, starting with the original Wigner's Friend setup and looking at other scenarios proposed more recently. I will argue that standard quantum mechanics, given eg in the celebrated Feynman Lectures textbook has no problems in dealing with such scenarios, though this involves underlying assumptions that are by no means obvious and might in the future prove to be incorrect.

9.

Name of the Speaker: Prof. Francesco Buscemi, Nagoya University, Japan

Title: Prediction, retrodiction, and the Second Law of Thermodynamics

Abstract: In this talk I will present some recent work clarifying the role that prediction and retrodiction (and, more generally, Bayesian inference) play in the logical foundations of the Second Law of Thermodynamics and various fluctuation theorems for classical and quantum systems. The exposition will be very much pedagogical, assuming only a little background in elementary probability theory, classical thermodynamics, and quantum (information) theory. Based upon https://arxiv.org/abs/2003.08548 and https://arxiv.org/abs/2009.02849

10.

Name of the speaker: Dr. Amit Rai, Jawaharlal Nehru University, New Delhi

Title: Non-classical light in a J_x photonic lattice

Abstract: We report the study of non-classical light in a photonic lattice having a parabolic coupling distribution, also known as a Jx photonic lattice. We focus on a two-photon Fock state, a two-photon N00N state, a single-mode squeezed state and a coherent state as inputs to the lattice. We investigate the possibility of a perfect transfer of the mean photon number as well as the quantum state from one waveguide mode to another. We study photon–photon correlation for the two-photon N00N state. For the single-mode squeezed state we perform a detailed study of the evolution of the squeezing factor and entanglement between the waveguide modes. Our findings suggest a perfect transfer of the average photon number in all cases and a perfect transfer of the quantum state in the cases of the two-photon Fock state and the two-photon N00N state only, but not in the cases of the squeezed and coherent states. Our results should have applications in the physical implementation of photonic continuous-variable quantum-information processing.

11.

Name of the speaker: Dr. Suddhasatta Mahapatra, IIT Bombay

Title: Quantum Computing with Electron Spins in Silicon

Abstract: The spin states of electrons represent a promising two-level-system for realization of a scalable quantum computing architecture. As the naturally abundant isotope of Silicon (28Si) has zero nuclear-spin , (enriched) Si serves as an ideal solid-state environment to host electron spin qubits, ensuring long coherence and relaxation times. Moreover, the physical implementation of the spin quantum computing architecture relies on the mature CMOS process technology, enabling large scale integration of dense arrays of spin qubits. In the past couple of years, tremendous advances have been made in this field, with demonstration of high-fidelity control, manipulation, and measurement of spin qubits, as well as methods to enable qubit coupling over long-distances. In this talk, starting from the fundamental concepts of spin quantum computing, I will present a brief overview of the prospects and challenges towards development of a scalable architecture.

12.

Name of the speaker: Dr. Stefanos Kourtis, Universite De Sherbrooke

Title: Classical and quantum computations as tensor networks

Abstract: Tensor networks are multilinear-algebra data structures that are finding application in diverse fields of science, from quantum many-body physics to artificial intelligence. I will introduce tensor networks and illustrate how they can be used to represent classical and quantum computations. I will then motivate tensor network algorithms that perform or simulate computations in practice and demonstrate their performance on benchmarks of current interest, such as model counting and quantum circuit simulation. I will close with an outline of ongoing work and an outlook on future directions.

13.

Name of the Speaker: Dr. Aikaterini Mandilara, Nazarbayev University, Kazakhstan

Title: Methods for characterizing multipartite entanglement in pure and mixed states

Abstract: The lecture is going to be divided into 3 parts. In the first part, the problem of characterizing multipartite entanglement is going to be exposed and then the algebraic method of nilpotent operators [1] is going to be presented as a general solution to this problem. The presentation is going to be based on simple, instructive examples. In the second part, the problem of identifying entanglement in mixed multipartite states is going to be first analyzed in a geometric way. On the same setting I will provide a geometric understanding of the best separable approximation, a unique representation providing a clear picture of the entanglement content of a state. Then I will explain the steps of an efficient algorithm [2] for achieving the best separable approximation and present examples which concern open quantum systems and bound entangled states. Finally, in the third part, I will talk about entanglement within continuous quantum variables. I will revise well-known results about entanglement of Gaussian states and then present a method for detecting entanglement on non-Gaussian mixed states [3]. The latter is based on a generalized uncertainty relation that takes into account the non-Gaussianity of a state.

[1] Quantum entanglement via nilpotent polynomial}s, A. Mandilara,V. M. Akulin, A. V. Smilga and L. Viola, Phys. Rev. A 74, 022331 (2006).

[2] Essentially Entangled Component of Multipartite Mixed Quantum States, its Properties and an Efficient Algorithm for its Extraction}, V. M. Akulin, G. A. Kabatyanski and A. Mandilara, Phys. Rev. A 92, 042322 (2015).

[3] Detection of non-Gaussian entangled states with an improved continuous-variable separability criterion}, A. Hertz, E. Karpov, A. Mandilara, N. J. Cerf, Phys. Rev. A 93, 032330 (2016).

14.

Name of the Speaker: Prof. Yueh-Nan Chen, National Cheng Kung University, Taiwan

Title: Benchmarking quantum state transfer in the Cloud

Abstract: Quantum state transfer (QST) provides a method to send arbitrary quantum states from one system to another. Such a concept is crucial for transmitting quantum information into the quantum memory, quantum processor, and quantum network. In this talk, I will first introduce the concept of EPR steering. I will then describe the temporal analogue of EPR steering, i.e. temporal quantum steering. For practical applications, I will show that the temporal steerability is preserved when the perfect QST process is successful. Otherwise, it decreases under imperfect QST processes. We then apply the temporal steerability measurement technique to benchmark quantum devices including the IBM quantum experience and QuTech quantum inspire under QST tasks. The experimental results show that the temporal steerability decreases as the circuit depth increases. Moreover, we show that the no-signaling in time condition could be violated because of the intrinsic non-Markovian effect of the devices.

Biography:

Professor Yueh-Nan Chen received the B.S. and M.S. degrees in Dep. of Electrophysics from National Chiao Tung University, Hsinchu, Taiwan, in 1996 and 1998, respectively. In 2001, he received the Ph.D. degree in Dep. of Electrophysics from National Chiao Tung University. He is a Professor in the Department of Physics at National Cheng-Kung University (NCKU). He is now also the director of Center for Quantum Frontiers of Research & Technology (QFort) at NCKU. His research interests include quantum transport, quantum optics, and quantum information.

15.

Name of the speaker: Prof. Emanuele Dalla Torre, Bar-Ilan University, israel

Title: Quantum simulations with quantum computers on the cloud: Floquet and topology

Abstract: Quantum computing holds the promise to solve specific computational problems much faster than any known classical algorithm. Current quantum computers are, however, too small and too noisy to perform useful calculations. In this talk I will follow a different route and show how to use these systems to study fundamental physical questions, and specifically those related to the dynamics of many-body quantum systems. I will focus on two specific applications of quantum computers on the cloud: the demonstration of the topological property of spin models [1] and the realization of a quantum system with long range interactions [2]. These works raise new basic questions concerning the effects of classical noise on quantum states of matter, and provide a useful benchmark for actual quantum computers.

1. Daniel Azses, Rafael Haenel, Yehuda Naveh, Robert Raussendorf, Eran Sela, Emanuele G. Dalla Torre, Identification of symmetry-protected topological states on noisy quantum computers, Physical Review Letters 125, 120502 (2020)

2. Mor M. Roses, Haggai Landa, Emanuele G. Dalla Torre, Simulating long-range hopping with periodically-driven superconducting qubits, https://arxiv.org/abs/2102.09590

16.

Name of the Speaker: Prof. Salvatore Savasta, University of Messina, Italy

Title: Ultrastrong coupling between light and matter

Abstract: Ultrastrong coupling between light and matter has, in the past decade, transitioned

from a theoretical idea to an experimental reality. In this new regime of quantum light–matter

interaction, beyond weak and strong coupling, the coupling strength

is comparable to the transition frequencies in the system.

Here we review the theory of quantum systems with ultrastrong coupling, discussing entangled ground states with virtual excitations, and new avenues for nonlinear optics. We also overview a subset of the multitude of experimental setups, including superconducting circuits, organic molecules, semiconductor polaritons, and optomechanical systems, that have now achieved ultrastrong coupling. I also discuss recent achievements of the so-called deep strong coupling regime, where the coupling strength becomes larger than the transition frequencies of the system. I conclude by discussing the potential applications enabled by these

achievements.

17.

Name of the speaker: Prof. Ashwani K. Tiwari, Indian Institute of Science Education and Research Kolkata, Mohanpur 741246

Title: Quantum Dynamics, Wavepacket and Coherent Control

Abstract: Time-dependent Schrödinger equation (TDSE) is the most fundamental equation in the quantum mechanics. My talk will focus on the different techniques to propagate wavepacket using the TDSE. Some examples of coherent control of chemical reactions using wavepacket dynamics will also be discussed.

References

1. N. Balakrishnan, C. Kalyanaraman, and N. Sathyamurthy, Physics Reports 280, 79 (1997). 2. A. K. Tiwari and N. E. Henriksen J. Chem. Phys., 144, 014306 (2016).

3. A. K. Tiwari and N. E. Henriksen J. Chem. Phys., 141, 204301 (2014).

4. A. K. Tiwari, D. Dey, and N. E. Henriksen Phys. Rev. A, 89, 023417 (2014).

18.

Name of the speaker: Dr. Said Sakhi, American University of Sharjah, USA

Title: Theoretical foundation of Josephson junction dynamics

Abstract: The Josephson junction effect (JJE) is one of the remarkable manifestations of quantum effects in condensed matter physics. It offers the potential to control and to manipulate the macroscopic wave function of a condensate, and it provides a wide variety of stimulating applications in quantum technologies. In this pedagogical talk, after introducing the essential physics of superconductivity, I discuss the theoretical foundation of Josephson dynamics and I highlight the peculiar features of Josephson phenomena using Ginzburg–Landau (GL) theory. This material should facilitate the description of solid state realization of a quantum computer that makes use of superconducting qubits based on Josephson junctions.

19

Name of the speaker: Prof. Marcin Pawłowski, University of Gdansk, Poland

Title: Information Theoretic Principles of Quantum Mechanics

Abstract: The violation of Bell Inequalities is arguably the strangest property of the quantum theory. It forces us to abandon intuitive principles of either locality or realism and leaves us with a lot of questions: If these principles should not be taken for granted, which should? Can the quantum theory be derived from operational principles in a way similar to relativity? Are some principles better than the others?

In this talk I will try to give the partial answers to these questions. Since deriving all the predictions of quantum theory seems like a monumental task, I will focus on something simpler but still far from trivial – deciding if a given probability distribution could be generated in a quantum experiment of a certain structure. This is what the studies of information theoretic principles aim to achieve.

I will present a few most well known principles and discuss motivation behind each of them, their predictive strengths and drawbacks. I’ll conclude with the latest results in the field.

20.

Name of the speaker: Prof. Dieter Suter, TU Dortmund, Germany,

Title: Quantum information processing with hybrid quantum registers based on individual electronic and nuclear spins

Abstract: The "Digital Revolution" that transformed our lives and our economy is based on the ubiquity of information-processing devices whose processing power increased exponentially for many decades, following Moore's law. As this trend is approaching fundamental physical limits, new directions are explored for even more powerful computational devices based on quantum mechanical systems. Such devices can solve problems that will remain out of reach for conventional (super-)computers. This talk will provide an introduction into a specific physical platform for quantum information processing, which uses individual electronic and nuclear spins in defect centers in diamond and SiC. The combination of different types of qubits allows one to take advantage of the favourable properties of each type but also poses some challenges. We describe the relevant properties of these centers and show how the different degrees of freedom can be controlled effectively and efficiently.

21.

Name of the speaker: Prof. Lorenzo Maccone, University of Pavia, Italy

Title: The four postulates of quantum mechanics are three

Abstract: The tensor product postulate of quantum mechanics states that the Hilbert space of a composite system is the tensor product of the components' Hilbert spaces. All current formalizations of quantum mechanics that do not contain this postulate contain some equivalent postulate or assumption (sometimes hidden). Here we give a natural definition of composite system as a set containing the component systems and show how one can logically derive the tensor product rule from the state postulate and from the measurement postulate. In other words, our paper reduces by one the number of postulates necessary to quantum mechanics.

22.

Name of the speaker: Prof. Vinod Menon, The City College of New York, USA

Title: Light based Hamiltonian simulators

23.

Speaker: Prof. S. Lakshmi Bala, Department of Physics, IIT Madras

Title of talk: What can we learn about the state of light from optical tomograms?

Abstract: Extraction of information from patterns is an important tool in a variety of diverse areas ranging from medical science where images carry details of the scanned object, to linguistics where patterns in the structure of sentences facilitate natural language processing, and provide information on the thoughts behind a string of words. In all these disciplines, much is inferred from the images or patterns, and further detailed

investigations are often proved to be merely corroborative of the lessons learnt from them. This aspect is true of optics as well. The optical tomograms or patterns obtained directly as histograms from the experiment can be used to extract information on nonclassical effects such as squeezing properties, quantum entanglement and revivals of the state of light when it propagates through a nonlinear optical medium. In this talk, I will present some aspects

of optical tomograms, and the message that lies buried in them.

24.

Speaker: Dr. B. Sharmila, Department of Physics, IIT Madras

Title: Tomographic entanglement indicators from an NMR experiment and from the IBM quantum computing platform

Abstract: In this talk, we demonstrate the advantages of the tomographic entanglement indicators in the context of spin and hybrid quantum systems. We use data from an NMR experiment and compare the results with those obtained from performing both experiment and simulation using the IBM quantum computing program. First, the tomographic entanglement indicators from the NMR experiment are shown to agree well with standard entanglement measures calculated from the corresponding density matrices. Further, these indicators compare well with those obtained from the experimental execution and simulation of equivalent circuits corresponding to the NMR experimental set-up, using the IBM quantum computing platform. This exercise is also extended to the case of a hybrid quantum system described by the double Jaynes-Cumming model.

25.

Name of the speaker: Dr. Sai Vinjanampathy, IIT Bombay

Title: Introduction to Variational Quantum Algorithms.

Abstract: Since quantum evolution is difficult to simulate on a classical computer, there is a recent push to use quantum computers to directly solve problems such as estimating the ground states of molecules. I will discuss the basic idea of "variational quantum algorithms" in the context of NISQ devices. I will take the students through "zoom blackboard" lectures that discuss (a) Setting up an ansatz for a quantum state, (b) setting up a representation for Hamiltonians and unitaries, (c) measuring various scalar quantities of interest and (d) some issues with optimization of functionals on NISQ computers that are the topic of discussion in the literature.

26.

Name of the speaker: Dr.Kavita Dorai, IISER Mohali

Title: Quantum Information Processing Using Nuclear Spins as Qubits and Qudits

Abstract: Nuclear magnetic resonance (NMR) quantum computers were one of the first and the most successful quantum technologies to be used as a testbed for quantum information processing. This talk will begin with an overview of using nuclear spins as qubits and qudits for quantum information processing and will detail some of the early successes in the field, including experimental implementations of quantum algorithms and quantum simulation.

The later part of the talk will focus on some of the current challenges that this quantum technology is facing.

27.

Name of the speaker: Dr. Ashok Kumar, IIST Trivandrum

Title: Spatial quantum correlation properties of bright twin beams of light

Abstract: Spatial quantum correlations promise to enhance the sensitivity of quantum imaging and quantum sensing, along with applications in quantum information processing. We will discuss spatial quantum correlation properties of bright twin beams of light generated with a four-wave mixing process in hot rubidium vapour cell. We will start with a general motivation of how the spatial correlation properties led to the famous Einstein-Podolsky-Rosen (EPR) paradox, and then introduce the experimental scheme that we have implemented to realize the EPR paradox with a macroscopically large number of photons. We use an electron-multiplying charge-coupled device camera to record images of the bright twin beams in the near and far field regimes to achieve an apparent violation of the uncertainty principle by more than an order of magnitude, which remains statistically significant even in the limit of a small number of images. We will also present some of our results on how the spatial distribution of cross-correlations of spatial noises of the twin beams can be engineered.

28.

Name of the speaker: Prof. Anirban Pathak, Jaypee Inst. Inf. Tech. Noida, India

Title: The notion of security in the quantum world: advantages, expectations and challenges

Abstract: We will briefly introduce the notion of unconditional security in the context of quantum communication and multiparty computation. Expected advantages of the quantum and semi-quantum schemes over their classical counterparts will be discussed in detail with particular focus on the technological limitations. Specifically, it will be shown that the device imperfections can be exploited to perform quantum hacking.

29.

Name of the speaker: Dr. Swarnamala Sirsi, Yuvaraja’s College

Title: Joint measurability of qubit, qutrit operators

30.

Name of the speaker: Prof. Urbasi Sinha, Raman Research Institute, Bangalore

Title: Exotic world in the foundations of quantum mechanics: Precision experiments and beyond

Abstract: In this talk, I will present an overview on some of the work that is being pursued at the Quantum Information and Computing lab at Raman Research Institute, Bangalore particularly in the domain of experimental photonic quantum science and technologies. A photon being the fundamental unit of light presents itself as an ideal test bed for precision testing of the foundations of quantum theory ranging from phenomena related to interference, superposition, entanglement as well as quantum measurements. Through several experiments over the last decade, we have been probing and utilizing these fundamental phenomena on the one hand towards better understanding of the principles of quantum mechanics and on the other hand towards applying such knowledge in applications ranging from quantum metrology, quantum information processing as well as secure quantum communications. I will attempt to discuss some of this exciting journey in this talk, especially discussing our exciting results in higher dimensional quantum information, new findings related to the Hong-Ou-Mandel effect, newly devised method for precise quantum state estimation which we call quantum state interferography as well as our experiments towards long distance secure quantum communications as a part of our project on quantum experiments using satellite technology.

31.

Name of the speaker: Dr. Debasis Sarkar, University of Culcutta

Title: Local Distinguishability and Indistinguishability of Quantum States- A Brief Introduction

Abstract: Distinguishability of quantum states has an immense importance in quantum information processing. For perfect discrimination, the set of states must be mutually orthogonal. However, for composite systems the situation is quite different. In such cases, it would be preferred to restrict the set of allowable operations to be local in nature (i.e., LOCC). It is really hard to distinguish locally a set of quantum states (entangled or not) shared between a number of parties situated at distant places. Rather, it shows many counter-intuitive results in quantum information theory. It is found that some orthogonal product states are locally indistinguishable. In contrast, there are orthogonal entangled states that are locally distinguishable. The study in this direction was motivated by the discovery of ‘quantum non-locality without entanglement’, which establishes a very strange phenomenon that there are sets of orthogonal product states, not LOCC distinguishable. Quantum nonlocality without entanglement in a multipartite quantum system is still incompletely studied except for some special class of completely orthogonal product bases(COPB) and some unextendible product bases(UPBs). In this lecture, we will try review some of the important results regarding the above issues and lastly we will show our recent results on tripartite systems, a direction to probe multipartite quantum systems.

32.

Name of the speaker: Dr. Ashoka S. Vudaygiri, University of Hyderabad, India

Title & Abstract:

1. Quantum Key Distribution - I will discuss the basics of the QKD

2. Quantum Computation in cold atoms using spin - spin interaction.

33.

Name of the speaker: Prof. Halliwell, Jonathan J, Imperial College London, Singapore

Title: Aspects of Leggett-Garg Tests of Macrorealism

34.

Name of the Speaker: Prof. Sonjoy Majumder, Head, Centre for Theoretical Studies, IIT-Kharagpur

Title: Quantum control of spin-oscillation dynamics of ion-atom mixture using external field

Abstract: The study of trapped ions immersed in ultra-cold atomic gas is one of the most challenging coveted for quantum simulations and quantum computations. Spin dynamics of ions or atoms of the system under external fields can be exploited for quantum gates and circuits. Here we will discuss the light-control mechanism of the spin-exchange process among the ions and atoms under a magnetic field. The spin-oscillation property can predict different properties of the atomic gas once the inter-atomic interaction is considered.

Reference:

1) M. Tomaza, et al., Rev. Mod. Phys., 91, 035001 (2019)

2) A Bhowmik, N N Dutta, and S Majumder, Phy. Rev. A, 102. 063116 (2020)

35.

Name of the speaker: Dr. Anand Kumar Jha, IIT Kanpur, India

Title: Partial coherence: Applications in quantum state measurement, imaging and communication

Abstract: Fields with quantum correlations are resources to several quantum-information applications as they could be exploited for performing tasks that would otherwise be impossible. One of the major challenges faced in the implementation of several quantum-information protocols is the efficient measurement of quantum states and quantum correlations, especially the high-dimensional quantum states. In this talk, I will present how partial coherence properties could be utilized for efficient measurement of high-dimensional quantum states and correlations. I’ll also present some of our work on the applications of partially coherent light fields for imaging and communication.

36.

Name of the Speaker: Dr. Bhaskar Kanseri, Experimental Quantum Interferometry and Polarization (EQUIP), Department of Physics, Indian Institute of Technology Delhi, Hauz Khas, New Delhi-110016, India , Email:bkanseri@physics.iitd.ac.in

Title: Quantum state engineering using hybrid variable resources for quantum informatics

Abstract: Hybrid variable quantum resources refer to the use of both continuous variable and discrete variable tools available in quantum physics. Both of these resources have been widely explored independently and have found several existing applications in quantum domain. However, since each of them has some benefits (shortcomings) over the other, their use in a complementary or joint manner may be quite advantageous. For instance, using them together, one can generate and characterize more exotic non-classical and non-Gaussian states of light [1]. This talk aims to familiarize students about this quantum optical toolkit and demonstrate the use of these hybrid resources for generation of single photon states and optical Schrödinger’s cat state. The role of cavities in pulsed domain would also be highlighted and we will see that one can employ synchronized pulse optical cavities for second harmonic generation [2], to approximate as an on-demand quantum source [3], for Fock state generation and realization of all cavity Schrödinger cat state for quantum information applications. We finally look forward to highlight some of our recent attempts using this quantum toolkit towards realizing methods for secure quantum communication in free space and optical fibres.

References:

1. J. Etesse, M. Bouillard, B. Kanseri and R. Tualle-Brouri, Phys. Rev. Letts. 114, 193602 (2015)

2. B. Kanseri, M. Bouillard and R. Tualle-Brouri, Opt. Commun. 380, 148 (2016)

3. M. Bouillard, G. Boucher, J. F. Ortas, B. Kanseri, and R. Tualle-Brouri, Opt. Expr. 27, 3113 (2019)

37.

Name of the speaker: Prof. Luiz Davidovich, Universidade Federal do Rio de Janeiro, Brazil

Title: Physics, information, and the new quantum technologies

38.

Name of the Speaker: Prof. Krishna Thyagarajan , Bennett University, India

Title: The quantum nature of light and the Photon

39.

Name of the Speaker: Dr. Debashis Saha,

Title - Introduction to self-testing

Abstract - To realize genuine quantum technology, the back-end user should be ensured that the quantum devices work as specified by the provider. Methods to certify that a quantum device operates in a nonclassical way are therefore needed. Among various certification methods, the most compelling one is self-testing (or blind-tomography). It exploits quantum nonlocal correlations and provides the complete characterization of quantum devices without any assumption on the internal features of the devices. This talk will be an introduction to self-testing.

40.

Name of the speaker: Dr. Sankar De, Saha Institute of Nuclear Physics, HBNI, Kolkata, India.

Title: Electromagnetically Induced Transparency: Quantum memory and Atomic magnetometry

Abstract: The light-atom interaction is one of the key research areas in the present time due to its vast applications in the various fields along with its fundamental interest. Using quantum optical methods, one can control the properties of an atomic medium with lasers and therefore can create a new medium with distinctive characteristics. Atoms can be prepared in a coherent superposition of energy states under the interaction of two or more laser fields which are resonant with various atomic transitions. Among these, in a three-level atomic system, electromagnetically induced transparency (EIT) occurs when a strong control or pump laser induces a narrow spectral transparency window at a highly absorbing atomic resonance for a weak probe laser beam by creating coherence between the relevant atomic states. As a result, the properties of the atomic vapour are changed dramatically and in the vicinity of EIT, the medium becomes very dispersive. This leads to interesting phenomena culminating into observation of slow light and storage and precision atomic magnetometers. I shall briefly discuss these developments in my talk.

41.

Name of the Speaker: Prof. Guruprasad Kar, Physics and Applied Mathematics Unit, Indian Statistical Institute

Title: Understanding Quantum Nonlocality

Abstract: Quantum mechanics has no contradiction with principle of relativity implying it is consistent with no-signaling condition. J.S. Bell proved that quantum mechanical correlations do not necessarily satisfy local realistic condition (put forward by Einstein) and quantum mechanics is nonlocal only in this sense. The issue of quantum nonlocality will be discussed by invoking some simple multipartite games.

42.

Name of the speaker: Dr. Ashutosh Rai, Researcher, Slovak Academy of Sciences, Bratislava

Title: Communication Cost of Simulating Entanglement

Abstract: Say, two non communicating and space-like separated parties Alice and Bob share some entangled state, and perform on their respective parts some local measurement chosen randomly from their set of incompatible measurements. Then it is well known that non-classical correlations can result in the joint probability distribution of the outcomes of Alice and Bob. Such non-classical feature is witnessed by violation of some Bell-type inequality. Entanglement is a necessary condition for witnessing this non-classical effect. Then question of interest is to ask what is the minimal communication cost of simulating (non-classical) quantum correlations generated by some given states and measurements. In this talk, I plan to present on this topic and outline some open problems on the topic.

43.

Name of the speaker: Prof. Sivakumar Srinivasan, Krea University

Title: Jaynes-Cummings-model and circuit QED.

44.

Name of the speaker: Dr. Manabendra Nath Bera, IISER Mohali

Title: Quantum Heat Engines with Carnot Efficiency at Maximum Power

Abstract: Conventional heat engines, be these classical or quantum, with higher power yield lesser efficiency and vice versa and respect various power-efficiency trade-off relations. Here we show that these relations are not fundamental. We introduce quantum heat engines that deliver maximum power with Carnot efficiency in the one-shot finite-size regime. These engines are composed of working systems with a finite number of quantum particles and are restricted to one-shot measurements. The engines operate in a one-step cycle by letting the working system simultaneously interact with hot and cold baths via semi-local thermal operations. By allowing quantum entanglement between its constituents and, thereby, a coherent transfer of heat from hot to cold baths, the engine implements the fastest possible reversible state transformation in each cycle, resulting in maximum power and Carnot efficiency. We propose a physically realizable engine using quantum optical systems.

45.

Name of the speaker: Anant V. Varma, IISER Kolkata

Title: Simulating non-Hermitian dynamics of a multi-spin quantum system and an emergent central spin model.

Abstract: In recent times there has been much discussion of non-Hermitian quantum systems in the context of many-body systems owing to the exotic manifestations like a violation of Lieb-Robinson bound (PRL 124,136802 (2020)), non-Hermitian skin effect (PRL 121, 086803 (2018)), suppression of defect production in Kibbel-Zurek mechanism (Nature Comm. 10, 2254 (2019)) and correspondence between (d+1) dimensional gapped Hermitian systems and d-dimensional point-gapped non-Hermitian systems (PRL 123, 206404 (2019)). Hence a possibility of simulating such a system that will facilitate the direct observation of such phenomena could be of great importance. It is known that the dynamics of a single spin-1/2 PT-symmetric system can be simulated by conveniently embedding it into a subspace of a larger Hilbert space with unitary dynamics. In the context of many-body physics, what would be the consequence of the complexity of such ideas of embedding non-Hermitian many-body systems in unknown. We show that such an embedding leads to non-trivial Hamiltonian which has complex interactions. We consider a simple example of N free PT-symmetric spin-1/2s to obtain the resulting many-body interacting Hamiltonian of N+1 spin-1/2s. We can visualize it as a strongly correlated central spin model with the additional spin-1/2 playing the role of central spin. We would show that due to the orthogonality catastrophe, even a vanishing small exchange field applied along the anisotropy axis of the central spin leads to a strong suppression of its decoherence arising from spin-flipping perturbations.

This talk would be based on the following paper: Anant V. Varma, and Sourin Das, Simulating non-Hermitian dynamics of a multi-spin quantum system and an emergent central spin model” arXiv:2012.13415 (communicated to Phys. Rev. B) .

46.

Speaker: Dr. Ayan Khan, Bennett University

Title: Understanding some Exhotic Phases of Matter and Their Implication in Quantum Technology

Session: Quantum Chemistry & Applications to Condensed Matter Physics

Abstract: Ultra-cold atomic gases are considered as the ultimate testing ground for condensed matter physics theories as one can engineer the dynamics of these extremely cold atoms quite precisely and effectively. Of late, several new experimental evidences have emerged, inspiring us to relook at the conventional understanding of liquid and solid. In this lecture, we plan to introduce a couple of exciting phases which have been observed very recently. Among them, the quantum droplet is the liquid-like state which does not follow the conventional Van der Waals theory. The other entity, known as supersolid, is as unique as its name suggests. It is a spatially ordered material with superfluid properties. An introduction to these phases will enable us to comment on their implications in quantum technology.

47.

Name of the speaker: Dr. P. D. Duraga Nandini, Pune University

Title: Factorization, coherence and asymmetry in the Heisenberg spin-1/2 XXZ chain with Dzyaloshinskii-Moriya interaction

Abstract: A certain class of quantum phase transitions(QPT) are associated with the intriguing property of the existence of a non-trivial 'factorizability' property, i.e., the quantum state becomes completely separable at certain parameter strengths which serve as precursors signalling the existence of a QPT associated with an entanglement transition(ET); there is a crossover from one type of entanglement to another across the factorizing field. The most notable example is that of the Heisenberg spin S= 1/2 chain where it was shown several years ago that a factorizable ground state emerges at a certain value of the external magnetic field. We address here the question of the effect of Dzyaloshinskii-Moriya interaction (DMI) on the factorization, coherence and asymmetry properties of the ground state. We compute using numerical DMRG, various bipartite entanglement and coherence estimators like the one-tangle, two-spin-concurrence and Wigner-Yanase skew information measure. We show that a longitudinal DMI destroys the factorizability property(which physically manifests in the existence of a non-zero chiral spin current) whilea transverse DMI preserves it. We relate the presence(absence) of factorizability to the presence(breaking) of the $U(1)$ rotation symmetry about the local magnetization axis at each lattice site. We show that although the longitudinal DMI destroys the factorization property, there is a 'pseudofactorizing' field at which the violation of the $U(1)$ symmetry is minimal. An entanglement crossover occurs across this field which is characterized by an enhanced but finite range of two-spin concurrence in its vicinity in contrast with the diverging range of the concurrence for the ET across the factorizing field. We discuss also the relation of the asymmetry to the 'frameness' or the abililty to specify a full reference frame for the many body state.

References:

Pradeep Thakur and P. Durganandini, Phys.Rev. B 102, 064409 (2020); Pradeep Thakur and P. Durganandini, 2021

48.

Name of the speaker: Prof. Binayak S. Choudhury, Department of Mathematics, IEST, Shibpur

Title: FUNDAMENTALS OF QUANTUM COMMUNICATION.

49.

Name of the speaker: Prof. Tabish Qureshi, Centre for Theoretical Physics, J.M.I., New Delhi.

Title: Wave-Particle Duality and the Quantum Eraser

Abstract: Wave and particle natures are two complementary aspects of quantum objects, and are believed to be mutually orthogonal. In interference experiments, which are the testbed of wave-particle duality, the information about which of the different possible ways, a particle followed, construes its particle nature. How good is the interference that the particle shows, construes its wave nature. If the "which-way" information about a particle exists, the interference is lost. An interesting concept is that if the potential "which-way" information, stored in a quantum device, is erased, the interference, which was lost, can come back. This phenomenon is called "quantum erasure." There has been a long standing debate on the meaning of quantum erasure, and whether the choice regarding erasing the which-way information can be made after the particle has already hit the screen. This would imply that the particle can be "retrocausally" forced to behave like a particle or a wave, much after it has hit the screen. These concepts will be explained and clarified in the talk.

50.

Name of the Speaker: Prof. Aditi Sen De, Harish - Chandra Research Institute

Title: Quantum Communication (without security)

Abstract: The quantum theory of nature, formalized in the first few decades of the 20th century, contains elements that are fundamentally different from those required in the classical description of nature. Based on the laws of quantum mechanics, in recent years, several discoveries have been reported which can revolutionize the way we think about modern technologies. I will talk about such inventions in the field of communication and some of the recent results towards building communication network.

51.

Name of the speaker: Prof. Chiranjib Mitra, IISER Kolkata

Title: Experimental quantification of entanglement in low dimensional spin systems

Abstract: We report the macroscopic entanglement properties of a low dimensional quantum spin system by investigating its magnetic properties at low temperatures and high magnetic fields. The temperature and magnetic field dependence of entanglement from the susceptibility and magnetization data is performed and comparison is made with corresponding theoretical estimates. Extraction of entanglement has been made possible through the macroscopic witness operator, magnetic susceptibility and heat capacity. The spin systems studied exhibit quantum phase transition (QPT) at low temperatures, when the magnetic field is swept through a critical value. We show explicitly, using tools used in quantum information processing (QIP), that quantum phase transition (QPT) can be captured experimentally using quantum complementary observables. Entanglement properties of the same quantum spin systems when investigated by heat capacity measurements also capture the QPT.

52.

Name of the Speaker: Prof. Dipankar Home, Bose Institute, India

Title: Guaranteeing the Certainty of Randomness: Interface with No-signalling and Nonlocality

Abstract: Randomness is a fundamental feature of nature, and a key resource for myriad applications in diverse areas of physical and biological sciences, including, in particular, communication and cryptography. For such applications, certifying and quantifying Genuine Randomness (GR) is a crucial issue, which requires true unpredictability to be guaranteed in the presence of uncontrollable imperfections, and even if there is adversarial tampering of the random number generating device. The present talk will focus on this specific issue.

The talk will begin by pointing out the fundamental inadequacies of the currently available random number generating devices. Next, it will be explained how the argument based on solely the fundamental physical principle of No-signalling provides a way forward by enabling the use of nonlocal correlations embodied in quantum entanglement for certifying GR in the device-independent scenario. This will be illustrated with respect to both the Bell-CHSH inequality, as well as the Hardy and the Cabello-Liang relations.

In conclusion, the discussion will be confined to outlining the methods adopted for quantifying such certified GR in terms of the guaranteed minimum and maximum achievable bounds of GR, thereby giving a broad idea of how the key relevant results are obtained. For further details regarding this line of studies which have revealed a number of significant features of the relationship between the amounts of randomness, nonlocality and entanglement, one may look at the following mentioned works [1,2,3]:

1. S. Pironio, A. Acin, S. Massar, A. B. de la Giroday, D. N. Vaskevitch, P. Maunz et al., Random numbers certified by Bell’s theorem, Nature 464 (2010) 1021–1024.

2. A. Acin, S. Massar and S. Pironio, Randomness versus nonlocality and entanglement, Phys. Rev. Lett. 108 (2012) 100402.

3. S. Sasmal, S. Gangopadhyay, A. Rai, D. Home and U. Sinha, Genuine randomness vis-a-vis nonlocality: Hardy and Hardy type relations, arXiv:2011.12518 (2020).

53.

Name of the speaker: Prof. Cyril BRANCIARD, French National Centre for Scientific Research

Title: Quantum indefinite causal relations

Abstract: Quantum theory allows for processes where events happen in some indefinite causal order. A new field has emerged in the last decade, that aims at investigating the kind of indefinite causal relations that can be found in the quantum world, and at looking for potential applications. I will give an overview of this new domain, and present some of the latest results in the area.

54.

Name of the Speaker: Prof. Archan S. Majumdar, SNBCBS

Title : Single shot quantum correlations shared by multiple observers

Abstract: We explore the possibility of sharing of quantum correlations in single copies of two- and three-qubits by multiple parties. Various types of nonlocal quantum correlations, such as Bell-CHSH nonlocality, quantum steering, and entanglement detection are considered. We find the upper bound on the number of sequential observers who can share the above different kinds of correlations. This opens up the possibility of resource efficient quantum information processing involving multiple parties without having to create and preserve either multipartite entangled states, or many copies of bipartite entangled states.

55.

Name of the speaker: Dr. Neetik Mukherjee, Department of Chemical Sciences, IISER Kolkata

Title: Confined quantum systems and Information entropy in Chemistry

Abstract: Since its inception, confined quantum systems has emerged as a subject of topical interest. In such stressed environment, the rearrangement of atomic orbitals leads to increase in coordination number. Atoms, molecules confined under cavities of varying size and shape, exhibit distinct fascinating changes in their physical and chemical properties from their free counterpart. Atoms under high pressure were first studied as early as 1937. Such a situation can be modeled by shifting the spatial boundary from infinity to a certain finite region. Depending upon the capacity of pressure one can simulate them by invoking two broad categories of confining potentials, impenetrable (hard) and penetrable (soft). A new virial-like theorem has been proposed for these systems. In recent years, appreciable attention was paid to investigate various information measures, namely, Fisher information (I), Shannon entropy (S), R enyi entropy (R), Tsallis entropy (T), Onicescu energy (E), and several complexities in a multitude of physical and chemical systems including central potentials. In confined condition S and E has been successfully used to uncover the effect of confinement on Compton profiles (CP). A deeply bound electron has a very flat and broad momentum distribution. As a consequence, its CP is also broad. This broadness of distribution can be quantified by S, E. Hence, these measures can act as descriptors about the bound effect on an electron within a quantum system. Current study will convincingly establish this interpretation.

References:

1. Analysis of Compton profile through information theory in H-like atoms inside impenetrable sphere, Neetik Mukherjee and Amlan K. Roy, J Phys. B 53, 253002, (2020).

2. A quantum mechanical virial-like theorem for confined quantum systems Neetik Mukherjee and Amlan K. Roy, Phys. Rev. A 99, 022123 (2019).

3. Information-entropic measures in free and confined hydrogen atom, Neetik Mukherjee and Amlan K. Roy, Int. J. Quant. Chem. 118 e25596 (2018).

4. Quantum confinement in an asymmetric double-well potential through energy analysis and information entropic measure. Neetik Mukherjee and Amlan K. Roy, Ann. Phys. (Berlin) 528 412 (2016).

5. Information entropy as a measure of tunneling and quantum confinement in a symmetric double-well potential. Neetik Mukherjee , Arunesh Roy and Amlan K. Roy, Ann. Phys. (Berlin) 527 825 (2015).

56.

Name of the Speaker: Dr. Ritabrata Sengupta, IISER Berhampur

Title: Quantum channels, PPT channels, and all that

57.

Name of the Speaker: Dr. Arpita Maitra

Title: Quantum Supremacy and Its Implementation in Likelihood Theory with Quantum Coins and Computers

Abstract: In this talk, we discuss quantum supremacy, controversy with the term "supremacy" and its application in several fields like computation, communication, and security. Quantum supremacy comes in different forms; as processors/circuits, as entanglement, and as no cloning theorem. In the present talk, we show how entanglement provides an advantage in quantum likelihood theory to distinguish two density matrices. We also show how we implemented this theoretical result in IBM quantum computers. Our experimental results showed that, whereas the theory matches with the simulation, it differs significantly when we run the programme in actual quantum processors. Finally, we discuss the future research avenues in this direction.

58.

Name of the Speaker: Prof. Supurna Sinha, RRI Bangalore

Title: Entropy and Geometry of Quantum States

59.

Name of the Speaker: Dr. Utpal Roy, IIT Patna

Title: Bose-Einstein condensate: Quantum Simulation and Quantum Information

60.

Name of the Speaker: Prof. Dr. Apoorva D Patel, IISC Bangalore, India

Title: Two Uses of the Density Matrix: Understanding Quantum Chaos and Quantum Machine Learning Kernel

Abstract: The density matrix generalises the concept of probability distribution to quantum theory. That offers a new perspective on many classical problems. (1) In classical physics, chaos is characterised as rapid divergence of evolution trajectories that are infinitesimally separated to begin with. This definition does not directly apply to the quantum case because the overlap of two quantum states is invariant under unitary evolution. A phase space evolution scenario can get around this problem and help us understand quantum chaos. (2) Classification of data is a basic problem in machine learning. In supervised learning, the algorithm first determines the variational parameters that best separate the data, using known training datapoints. It can then predict the class labels of a new unknown datapoint. The kernel represents the overlap of states associated with the datapoints, and it can be chosen as the Hilbert-Schmidt inner product for convenient quantum processing and state discrimination.

61.

Name of the Speaker: Prof. Dr. MS Santhanam, IISER Pune, India

Title: Quantum entanglement and chaotic systems

Abstract: This talk will introduce how classical chaos affects quantum entanglement. It will cover some of the basic ideas and discuss some recent developments.

62.

Name of the Speaker: Prof. Dr. Ozawa Masano, Chubu University, Japan

Title: Soundness and completeness of quantum root-mean-square errors

Abstract: Quantifying the error of a measurement is fundamental to experimental sciences. In the classical physics, the root-mean-square (rms) error has been used for the standard error measure. The rms of the noise-operator, called the noise operator based error measure, has been used in quantum physics as a quantum counterpart of the classical rms error. The noise operator based error measure satisfies the following requirements: (I) operational definability (to be definable by the POVM, the measured observable, and the state); (ii) correspondence principle (to coincide with the classical rms error if the POVM and the observable commute); and (iii) soundness (to vanish for accurate measurements). However, it fails to satisfy (iv) completeness (to vanish only for accurate measurements), if the POVM and the observable do not commute. We discuss how to modify the noise operator based error measure to satisfy all requirements (i)--(iv). We obtain an error measure that satisfies (i)--(iv), and moreover, it is shown that the new error measure maintains the previously derived universally valid uncertainty relations and their experimental confirmations without changing their forms and interpretations, in contrast to a prevailing view that a state-dependent formulation for measurement uncertainty relation is not tenable. This talk is based on [M. Ozawa, Soundness and completeness of quantum root-mean-square errors, npj Quantum Inf. 5, 1 (2019)].

63.

Name of the Speaker: Prof. Dr. Prof. Marek Zukowski, University of Gdańsk, Poland

Title: Physics and Metaphysics of Wigner's Friends

64.

Name of the Speaker: Prof. Sivakumar Srinivasan, KREA University

Title: Jaynes-Cummings model and qubits

65.

Name of the Speaker: Debasish Parida & Uday Singla, IISER Kolkata. BITS Pilani

Title: Quantum Simulation of the Fermionic systems. (An introduction to Quantum Information in Quantum Chemistry.)

66.

Name of the Speaker: Dr. Kumar Abhinav, Nakhon Sawan Studiorum for Advanced Studies - NAS, Mahidol University, Nakhon Sawan 60130, Thailand.

Title: PT-symmetric and Pseudo-Hermitian Systems: Hilbert space, scattering and other aspects

Abstract: PT-symmetric systems have been at the forefront for more than a couple of decades, enveloping real physical systems beyond their Hermitian counterparts. Belonging to the larger class of pseudo-Hermitian systems, they support both real and complex-conjugate eigenvalues characterized by certain parametric phases. In this talk, we look into the vector space and conservation laws for these systems and find novel results that should be observable. Further, recent studies about field-theoretic applications of such systems are mentioned.

67.

Name of the Speaker: Dr. Rangeet Bhattacharyya, IISER Kolkata

Title: Quantum computation in open quantum systems: optimality of clock speeds

Abstract: We have recently demonstrated that quantum master equations could be extended to include the non-linear and dissipative terms from the drive acting on open quantum systems. We have also experimentally verified the theoretical predictions of drive-induced dissipation. In this talk, we show that such terms along with the system-bath interactions give rise to an optimal condition on qubit gate fidelity. We argue that the qubit gates have maximum fidelity only for a specific range of drive values; too weak or too strong a drive results in poor performance of a quantum circuit due to lower fidelity. We also demonstrate the universality of the results for the gate operations on single- and multiple-qubit gates.

68.

Name of the Speaker: Dr. Sanjib Dey, IISER Mohali

Title: Resources of quantum information theories with PT-symmetry and cavity optomechanics

Abstract: Studies on nonclassicality, entanglement and decoherence of quantum systems are some of the key areas of research in quantum information science. Analysis and development of such features based on resource theoretical frameworks have unveiled a new avenue in the last decade. Quantum resource theory is perhaps the most revolutionary framework that quantum physics has ever experienced. It plays vigorous roles in unifying the quantification methods of a requisite quantum effect as wells as in identifying protocols that optimize its usefulness in a given application in areas ranging from quantum information to computation. Moreover, the resource theories have transmuted radical quantum phenomena like coherence, nonclassicality and entanglement from being just intriguing to being helpful in executing realistic tasks. Along with the rapid growth of various resource theories corresponding to standard quantum optical states, significant advancement has been expedited along the same direction for generalized quantum optical states. Generalized quantum optical framework strives to bring in several prosperous contemporary ideas including nonlinearity, PT-symmetric non-Hermitian theories, etc., to accomplish similar but elevated objectives of the standard quantum optics and information theories. In this talk, I will discuss our recent developments in the given context and their usefulness in the areas of quantum information theories. Certain remarkable features of quantum optomechanics within the field will also be discussed alongside. More specifically, I will come up with realistic and experimental ideas of cavity optomechanics to generate resourceful states and their utilization in different areas of quantum information theory.

69.

Name of the Speaker: Dr. Shrobona Bagchi, Tel Aviv University Israel

Title : IID and problem specific samples of quantum states from Wishart Distributions

Abstract: Random samples of quantum states are an important resource for various tasks in quantum information science, and samples in accordance with a problem-specific distribution can be indispensable ingredients. Some algorithms generate random samples by a lottery that follows certain rules and yield samples from the set of distributions that the lottery can access. Other algorithms, which use random walks in the state space like the Monte Carlo, can be tailored to any distribution, at the price of autocorrelations in the sample and with restrictions to low-dimensional systems in practical implementations. We present a two-step algorithm for sampling from the quantum state space that overcomes some of these limitations. We first produce a CPU-cheap large proposal sample, of uncorrelated entries, by drawing from the family of complex Wishart distributions, and then reject or accept the entries in the proposal sample such that the accepted sample is strictly in accordance with the target distribution. We establish the explicit form of the induced Wishart distribution for quantum states. This enables us to generate a proposal sample that mimics the target distribution and, therefore, the efficiency of the algorithm, measured by the acceptance rate, can be many orders of magnitude larger than that for a uniform sample as the proposal. We demonstrate that this sampling algorithm is very efficient for one-qubit and two-qubit states, and reasonably efficient for three-qubit states, while it suffers from the "curse of dimensionality" when sampling from structured distributions of four-qubit states.

70.

Name of the Speaker: Dr. Stephan Sponar, TU Wien, Atominstitut - Institute of Atomic & Subatomic Physics

Title: Quantum measurements - Theory and Experiment

Abstract: The uncertainty principle is an important tenet and active field of research in quantum physics. Information-theoretic uncertainty relations, formulated using entropies, provide one approach to quantifying the extent to which two non-commuting observables can be jointly measured. Recent theo- retical analysis predicts that general quantum measurements (i.e. positive-operator valued measures) are necessary to saturate certain uncertainty relations and thereby overcome certain limitations of projec- tive measurements. Here, we experimentally test a tight information-theoretic measurement uncertainty relation with neutron spin-1/2 qubits.

71.

Name of the Speaker: Prof. Dipankar Home, Bose Institute

Title: Guaranteeing the Certainty of Randomness: Interface with No-signalling and Nonlocality

Abstract: Randomness is a fundamental feature of nature, and a key resource for myriad applications in diverse areas of physical and biological sciences, including, in particular, communication and cryptography. For such applications, certifying and quantifying Genuine Randomness (GR) is a crucial issue, which requires true unpredictability to be guaranteed in the presence of uncontrollable imperfections, and even if there is adversarial tampering of the random number generating device. The present talk will focus on this specific issue.

The talk will begin by pointing out the fundamental inadequacies of the currently available random number generating devices. Next, it will be explained how the argument based on solely the fundamental physical principle of No-signalling provides a way forward by enabling the use of nonlocal correlations embodied in quantum entanglement for certifying GR in the device-independent scenario. This will be illustrated with respect to both the Bell-CHSH inequality, as well as the Hardy and the Cabello-Liang relations.

In conclusion, the discussion will be confined to outlining the methods adopted for quantifying such certified GR in terms of the guaranteed minimum and maximum achievable bounds of GR, thereby giving a broad idea of how the key relevant results are obtained. For further details regarding this line of studies which have revealed a number of significant features of the relationship between the amounts of randomness, nonlocality and entanglement, one may look at the following mentioned works [1,2,3]:

1. S. Pironio, A. Acin, S. Massar, A. B. de la Giroday, D. N. Vaskevitch, P. Maunz et al., Random numbers certified by Bell’s theorem, Nature 464 (2010) 1021–1024.

2. A. Acin, S. Massar and S. Pironio, Randomness versus nonlocality and entanglement, Phys. Rev. Lett. 108 (2012) 100402.

3. S. Sasmal, S. Gangopadhyay, A. Rai, D. Home and U. Sinha, Genuine randomness vis-a-vis nonlocality: Hardy and Hardy type relations, arXiv:2011.12518 (2020).

72.

Name of the Speaker: Dr. Subhadeep De, Inter-University Centre for Astronomy and Astrophysics (IUCAA)

Title: Optical Clocks: An Indispensable Tool for Quantum Metrology & quantum Enabled Technology

Abstract: The optical atomic clock measures the “highly forbidden” atomic transition frequencies (clock transitions) in the optical domain with unprecedented accuracies. Neutral atoms stored in an optical lattice and a single atomic ion confined in an electrodynamic trap are the two most favorable approaches for building optical clocks. Apart from their use for accurate time-keeping, they are one of the most useful tools to hunt answers for several open science questions. Additional to the optical clocks, long-distance transfer of the phase preserved optical photons allows intercomparison of the geographically distributed clocks, which allows hunting for new physics such as the constancy of the dimensionless fundamental constants, violation of the fundamental symmetries, geodetic measurements, and so on. At the upcoming Precision & Quantum Measurement laboratory (PQM-lab: https://pqmlab.iucaa.in), IUCAA we are building a ytterbium-ion optical clock, which will be used to pursue quantum metrology, precision measurements, and developing quantum technologies. In this lecture, I shall focus on some of these science goals that we intend to pursue and recent development in the lab.

73.

Name of the Speaker: Prof. N D Chavda, Department of Applied Physics, Faculty of Technology & Engineering, The Maharaja Sayajirao University of Baroda

Title: Entanglement in Interacting Particle Systems

Abstract: In the present work, we study entanglement entropy in interacting particle systems modeled by embedded one- plus two-body random matrix ensembles for both fermion and boson systems. Also, participation ratio is studied and its correlations with entanglement entropy are analyzed. The results are consistent with those obtained using Bose-Hubbard model and spin models.

74.

Name of the Speaker: Dr. K. G. Paulson, Institute of Physics (IOP)-Bhubaneswar, India

Title: Speed of evolution of open quantum systems

Abstract: Quantum speed limit time defines the bound on the minimum time required for a quantum system to evolve between two states. It finds wide applications in various research fields such as quantum information processing, quantum computing, and quantum thermodynamics. Investigation of bounds on the speed of evolution of the system in open quantum dynamics is of fundamental interest, as it reveals the nature of the interaction between a quantum system and a bath. The behaviour of quantum speed limit time for initial pure and mixed states is investigated, and its connections with various channel properties are established. Dynamics of quantum correlation (QC) under (non-) Markovian dynamics are well studied; we discuss the relationship between quantum speed limit time and dynamics of QC under CP-(in) divisible unital and non-unital channels.

75.

Name of the Speaker: Sangita Majumdar, IISER Kolkata, India

Title: Energy and information analysis of spatially confined atoms through Density functional theory

Abstract: Atom trapped inside a cavity introduces fascinating changes in the observable properties. While an atom confined by rigid walls is a simple model to study electrons restricted to small regions, penetrable walls are more convenient to contrast the corresponding results with an experimental counterpart. Here we present few exploratory results obtained from a newly proposed DFT-based method in our laboratory to address such confinement in atoms. The radial Kohn-Sham (KS) equation is solved invoking a physically motivated non variational, work-function-based exchange potential, along with a simple parametrized local Wigner functional and a nonlinear, gradient- and Laplacian-dependent functional (LYP). GPS method is used to construct an optimized non-uniformly discretized spatial gridfor solving the KS equation. Preliminary results are presented for both ground and excited states of atoms and ions enclosed within impenetrable and penetrable cages. This includes external potential in the form of harmonic confinement, atom/ion embedded in a fullerene cage. The exchange-only results are practically of Hartree-Fock quality. The interplay between ordering and crossing of states as functions of cavity radius is analyzed by constructing a traditional correlation diagram. Study of such two-electron harmonium atom inside spherical cavity is pursued to conclude whether this crossing behaviour is unique to the one-electron coulomb potential or it can be observed in other single-particleconfining potential.

76.

Name of the Speaker: Prof. Ray-Kuang Lee, National Tsing Hua University, Taiwan

Title: Simulating non-Hermitian quantum systems by dilations

Abstract: Despite the initial motivation to establish an alternative framework of quantum theory, we can also take PT-symmetric systems as effective descriptions of large Hermitian systems in some subspaces [1, 2]. By using the Naimark dilation theorem, one can always find some four-dimensional Hermitian Hamiltonians to effectively realize two-dimensional unbroken PT-symmetric systems [3]. Then, passive PT-symmetric couplers can thus be implemented with a refractive index of real values and asymmetric coupling coefficients. This opens up the possibility to implement general PT-symmetric systems with state-of-the-art asymmetric slab waveguides, dissimilar optical fibers, or cavities with chiral mirrors [4]. As for the broken PT-symmetry, we disclose the relations between PT-symmetric quantum theory and weak measurement theory by embedding a PT-symmetric (pseudo-Hermitian) system into a large Hermitian one [5]. However, with only a global Hermitian Hamiltonian, how do we know whether it is a dilation and is useful for simulation? To answer this question, we consider the problem of how to extract the internal nonlocality in the Hermitian dilation. We unveil that the internal nonlocality brings nontrivial correlations between the subsystems. By evaluating the correlations with local measurements in three different pictures, the resulting different expectations of the Bell operator reveal the distinction of the internal nonlocality, which provides the figure of merit to test the reliability of the simulation, as well as to verify a PT-symmetric (sub)system [6].

Ref.:

[1] Yi-Chan Lee, Min-Hsiu Hsieh, Steven T. Flemmia, and RKL, "Local PT symmetry violates the no-signaling principle," Phys. Rev. Lett. 112, 130404 (2014); Editors' Suggestion; Featured in Physics: Reflecting on an Alternative Quantum Theory.

[2] Ludmila Praxmeyer, Popo Yang, and RKL, "Phase-space representation of a non-Hermitian system with PT-symmetry," Phys. Rev. A 93, 042122 (2016).

[3] Minyi Huang, RKL, and Junde Wu, "Manifestation of Superposition and Coherence in PT-symmetry through the $\eta$-inner Product," J. Phys. A: Math. Theor. 51, 414004 (2018).

[4] Yi-Chan Lee, Jibing Liu, You-Lin Chuang, Min-Hsiu Hsieh, and RKL, "Passive PT-symmetric couplers without complex optical potentials," Phys. Rev. A 92, 053815 (2015).

[5] Minyi Huang, RKL, Lijian Zhang, Shao-Ming Fei, and Junde Wu, "Simulating broken PT-symmetric Hamiltonian systems by weak measurement," Phys. Rev. Lett. 123, 080404 (2019).

[6] Minyi Huang, RKL, and Junde Wu, "Extracting the internal non-locality from the dilated Hermiticity," Phys. Rev. A (in press, 2021); [arXiv: 2009.06121].

77.

Name of the Speaker: Athira B S, IISER Kolkata, India

Title: Interferometric Weak measurement

Abstract: The weak value amplification concept, introduced by Aharonov, Albert, and Vaidman, has proven to be fundamentally important and extremely useful for numerous metrological applications. This quantum mechanical concept can be understood using the wave interference phenomena and can therefore be realized in classical optical settings also. The weak value amplification concept can be formulated within the realm of classical electromagnetic theory of light. In this regard, our recent experimental work on the realization of the weak value of polarization observable by introducing a weak coupling between the path degree of freedom of an interferometer and the polarization degree of freedom of light will be presented. There is an upper bound on the maximum achievable weak value amplification in the conventional linear response regime of weak measurements. On the conceptual ground, it is also equally important to understand the weak values through physically meaningful and experimentally accessible properties such as the system response function. In an attempt to address these issues, we have demonstrated a fundamental relationship between the weak value of an observable and complex zero of the response function of a system by employing weak measurement on spin Hall effect of a Gaussian light beam.

78.

Name of the Speaker: Prof. Aranya B Bhattacherjee, Department of Physics, Birla Institute of Technology and Science, Pilani,Hyderabad Campus, India

Title: Quantum Entanglement in Hybrid Systems

Abstract: Entanglement is one of the important elements of quantum mechanics as it is responsible for correlations between observables. I will first introduce some basic facts about entanglement and then go on to discuss some fundamental optomechanics. I will then discuss some hybrid optomechanical schemes where continuous variable entanglement can be realized between any two chosen degrees

of freedom. Such entanglement can lead to quantum state transfer between light and mechanical oscillators. In fact, entangled optomechanical systems have

potential profitable application in realizing quantum communication networks, in which the mechanical modes play the vital role of local nodes where quantum information can be stored and retrieved while optical modes carry this information between the nodes. In between I will show some recent experimental results.

79.

Name of the Speaker: Bhallamudi Vidya Praveen, IIT Madras, India

Title: Making use of relaxation of spins for spectroscopy and sensing

Abstract: Spins are being extensively pursued for quantum enhanced technologies. This follows long-standing work in magnetic /spin resonance where techniques for controlling and manipulating spins were extensively developed, leading to successful applications in the form of spectroscopic characterization tools for the lab and a medical diagnostic tool in the form of Magnetic Resonance Imaging. I will introduce these topics and then focus on how spin relaxation, which is generally considered a bane for quantum technologies, for performing sensitive spectroscopic measurements. In particular, I will look at the use of quantum defects in diamond for such applications.​

80.

Name of the Speaker: Prof. Sibasish Ghosh, IMSc, Chennai

Title: Universal schemes for detecting entanglement in two-mode Gaussian states: Stokes-like operator based approach

Abstract:-- Detection of entanglement in quantum states is one of the most important problems in quantum information processing. However, it is one of the most challenging tasks to find a universal scheme which is also desired to be optimal to detect entanglement for all states of a specific class – as always preferred by experimentalist. Although, the topic is well studied, at least in the case of lower dimensional compound systems (e.g., two-qubit systems), but in the case of continuous variable systems, this remains as an open problem. Even in the case of two-mode Gaussian states, the problem is not fully resolved. In our work, we have tried to address this issue. At first, a limited number of Hermitian operators is given to test the necessary and sufficient criterion on the covariance matrix of separable two-mode Gaussian states. Thereafter, we present an interferometric scheme to test the same separability criterion in which the measurements are being done via

Stokes-like operators. In such case, we consider only single-copy measurements on a two-mode Gaussian state at a time and the scheme amounts to the full state tomography. Although this latter approach is a linear optics based one, nevertheless it is not an economic scheme. Resource-wise a more economical scheme than the full state tomography can be obtained if we consider measurements on two copies of the two-mode Gaussian state at a time. However, optimality of the scheme is not yet known.

81.

Name of the Speaker: Prof. Pijushkanti Ghosh, Visva Bharati University

Title: Pseudo-hermitian quantum systems: Construction, Solvability, Supersymmetry

Abstract: After reviewing the basic ideas on PT-symmetric systems, mathematical formulation of

pseudo-hermitian system will be presented at an elementary level. In general, finding the operators relevant for defining the modified norm in the Hilbert space of a given quantum system is a non-trivial task for both PT-symmetric as well as pseudo-hermitian systems. Pseudo-hermitian systems with a pre-determined metric in the Hilbert space may be constructed from the known quantum systems via Dyson mapping. The construction of a few examples will be presented, which include pseudo-hermitian

Jaynes-Cummings model, Dicke model, transverse Ising model in one dimension, quadratic form of bosonic operators. The construction of pseudo-hermitian supersymmetric system will be presented.

82.

Name of the Speaker: Dr. Ananya Ghatak, University of Amsterdam, Netherlands

Title: Observation of novel bulk-edge correspondence in non-Hermitian metamaterials

Abstract: Topological edge modes are excitations that are localized at the materials’ edges and yet are characterized by a topological invariant defined in the bulk. Recently, the advent of non-Hermitian topological systems—wherein energy is not conserved—has sparked considerable theoretical advances. In particular, novel topological phases that can only exist in non-Hermitian systems have been introduced. We will discuss an experimentally observed novel form of bulk-edge correspondence for non-Hermitian topological phases. It shows, a change in the bulk non-Hermitian topological invariant corresponds to a

change of localization of the topological edge mode. With quantum-to- classical analogy we create a mechanical metamaterial with non-reciprocal

interactions, in which our predicted bulk-edge correspondence has been observed experimentally and witnesses its robustness. Such novel topological

features in non-Hermitian systems boost metamaterials by opening new avenues to manipulate waves in unprecedented fashions.

83.

Name of the Speaker: Dr. Rama Gupta, DAV College, India

Title: Insights of information Entropy in the Nonlinear World

84.

Name of the Speaker: Prof. Gautam Vemuri, Indiana University Purdue University Indianapolis, USA

Title: Delay-coupled semiconductor lasers as a platform for PT-symmetry

85.

Name of the Speaker: Prof. Bimalendu Deb, Indian Association for the Cultivation of Science (IACS)

Title: Exploring quantum information by atom-atom and atom-ion cold collisions

86.

Name of the Speaker: Dr. Manas Kulkarni,

Title: Localisation, Quantum State Transfer and emergent PT symmetry in non-Hermitian systems

Abstract: In the first part of the talk [1], we will discuss localization in cavity-QED arrays. We show that a careful engineering of drive, dissipation and Hamiltonian results in achieving indefinitely sustained self-trapping. We show that the intricate interplay between drive, dissipation, and light-matter interaction results in requiring an optimal window of drive strengths in order to achieve such non-trivial steady states. In the second part of the talk [2], we will discuss optimal protocols for efficient photon transfer in a cavity-QED network. This is executed through a stimulated Raman adiabatic passage scheme where time-varying inductive or capacitive couplings (with carefully chosen sweep rate) play a key role. In the third part of the talk [3], we will discuss emergent PT symmetry in a double-quantum-dot circuit-QED set-up. Starting from a fully Hermitian microscopic description, we show that a non-Hermitian Hamiltonian emerges in a double quantum dot circuit-QED set-up, which can be controllably tuned to the PT symmetric point. Our results pave the way for an on-chip realization of a potentially scalable non-Hermitian system with a gain medium in quantum regime, as well as its potential applications for quantum technology.

[1] A. Dey, M. Kulkarni, Phys. Rev. A 101, 043801 (2020)

[2] A. Dey, M. Kulkarni, Phys. Rev. Research 2, 042004, Rapid Communications (2020)

[3] A. Purkayastha, M. Kulkarni, Y. N. Joglekar, Phys. Rev. Research 2, 043075 (2020)

87.

Name of the Speaker: Dr. Aradhya Shukla,

Title: PT-symmetry and Supersymmetry: Broken and Unbroken Phases

88.

Name of the Speaker: Prof. Usha Devi A R

Title: Continuous Measurements on Open Quantum Systems: Quantum Diffusion

Abstract: Continuous probing of a quantum system through non-demolition measurements on the environment result in stochastic master equations. Depending on the nature of measurements one obtains quantum diffusion or jump type stochastic differential equations (also called Belavkin-Schrodinger equations). Study of quantum stochastic equations governing open system dynamics has gained importance in measurement and feedback based quantum control, which paves way to efficient parameter estimation. I discuss quantum stochastic differential equation for diffusion of a system and outline its implications in parameter estimation.

89.

Name of the Speaker: Prof. Jayendra Nath Bandyopadhyay, BITS Pilani, India

Title: Floquet Quantum Systems

Abstract: Periodically driven systems are ubiquitous in nature. These kinds of systems are studied theoretically using the Floquet theorem, hence these systems are also called Floquet systems. In this talk, I shall discuss the basics of Floqurt theory and systems and its application in designing quantum materials that may be useful in developing hardware for quantum computers.

90.

Name of the Speaker: Prof. V. Ravishankar

Title: Q in QIQT

Abstract: What is meant by quantum in quantum information? This question offers a number of perspectives, both in formal and applied domains, glimpses of which I shall provide in this talk.

91.

Name of the Speaker: Dr. Mamta Balodi, IISc Bangalore, India

Title: Categories, Functors and Natural transformations

Abstract: Almost half a century back, Eilenberg and Mac Lane gave us a revolutionary way of looking at Mathematical structures which are known as categories. This view point not only unifies. Mathematics but also breaks the barriers between different disciplines like Computer Programming, Quantum Information, Logic and Linguistics. In this talk, I will be introducing the basic notions of this discipline which are categories, functors and natural transformations by the way of examples.

92.

Name of the Speaker: Dr. Kazi Rajibul Islam, Institute for Quantum Computing (IQC) and Dept of Physics and Astronomy, University of Waterloo, Canada, Affiliate Scientist, TRIUMF and Perimeter Institute for Theoretical Physics

Title: Programmable Quantum Simulations with Laser-cooled Trapped Ions

Abstract: Trapped ions are among the most advanced technology platforms for quantum information processing. When laser-cooled close to absolute zero temperature, atomic ions form a Coulomb crystal with micron-scale spacings in a radio-frequency ion trap. Qubit or spin-1/2 levels, encoded in hyperfine energy states of each ion, can be initialized, manipulated, and detected optically with high precision. Laser fields can also couple the qubit states of arbitrary pairs of ions through (virtual) excitation of collective phonon modes, creating programmable quantum logic operations and spin Hamiltonians. In this talk, I will focus on programmable trapped-ion quantum spin simulators and explain how techniques from holographic optical engineering to machine learning can be combined to harness the power of these simulators. I will also describe the development of QuantumION, an open-access, multi-user quantum computing facility for the academic community.

93.

Name of the Speaker: Mr. Sooryansh Asthana, IIT Delhi, India

Title: Quantum communication using SU(2)–invariant 2 × N level separable states and its classical optical analogue

Abstract: Bloch vector contains the information encoded in a qubit. Employing this fact, we propose protocols for remote transfer of information in a qubit to a remote qudit using SU(2)– invariant 2 × N–level discordant (but separable) states as a quantum channel. These states have been identified as separable equivalents of the two-qubit entangled Werner states in [Bharath & Ravishankar, Phys. Rev. A 89, 062110]. We have also proposed a protocol for swapping of quantum discord from 2 × N–level states to N × N–level states. Employing these protocols, we believe that quantum information processing can be performed using highly mixed separable higher dimensional states. We show that the classical optical version of information transfer protocol can be employed for transferring information from the path to the orbital angular momentum degree of freedom of classical light

94.

Name of the Speaker: Prof.Jacob Biamonte, Skolkovo Institute of Science and Technology Moscow, Russia

Title: Results on variational quantum circuits to minimise effective Hamiltonians

Abstract: Modern quantum processors enable the execution of short quantum circuits. These quantum circuits can be iteratively tuned to minimise an objective function and solve problem instances. This is known as variational quantum computation: local measurements are repeated and modified to determine the expected value of an effective Hamiltonian. Whereas solving practical problems appears to remain out of reach, many questions of theoretical interest surround the variational model. I will explain some recent limitations found in collaboration, including reachability deficits in QAOA (i.e. increasing problem density — the ratio of constraints to variables — induces under parameterisation at fixed circuit depth), parameter saturations in QAOA (that layer-wise training plateaus) and the existence of abrupt trainability transitions (that a critical number of layers exists where any fewer layers results in no training for certain objective functions). I will also explain some more forward looking findings, including the concentration of parameters in QAOA (showing a problem instance independence of optimised circuit parameters) and my proof that the variational model is, in theory, a universal model of quantum computation.

95.

Name of the Speaker: Prof. Vyacheslav P. Spiridonov, Laboratory of Theoretical Physics, JINR, Dubna & Laboratory of Mirror Symmetry, NRU HSE, Moscow, Russia

Title: Solvable Potentials in Quantum Mechanics from Symmetry Reductions and Coherent States

Abstract: Solvable models of nonrelativistic quantum mechanics provide beautiful idealizations of reality. There is no completely regular way of generating them. We briefly describe the factorization method providing one of the options through reductions of an infinite chain of symmetry transformations. Self-similar potentials obtained in this way are described by very complicated nonlinear special functions including ordinary and q-deformed Painleve transcendents. They are related to polynomial quantum algebras, the q-harmonic oscillator algebra being the simplest case. Applications of these potentials to coherent states, solitons, Ising chains, Coulomb gases are shortly presented. In particular, we describe superpositions of coherent states of the harmonic oscillator associated with the parity and Fourier transformations.

96.

Name of the Speaker: Dr. Himadri Shekhar Dhar, IIT Bombay, India

Title: Light matter interaction in quantum technology

Abstract: In this talk, we look at the role of light-matter interaction in modern day quantum technology. We introduce the topic with a quick prelude to the origin of quantum optics and the field of cavity quantum electrodynamics, before touching upon the era of “artificial atoms” and “hybrid quantum systems.” However, the main focus of the talk will be to look at how one can work with simple theoretical models to study these systems and how by building light-matter interaction some important results can emerge that are useful from the perspective of quantum technology, such as generation of nonclassical light and quantum storage.

97.

Name of the Speaker: Nayana Das, ISI, Kolkata

Title: Two Efficient Measurement-Device-Independent Quantum Dialogue Protocols

Abstract: Quantum dialogue is a process of two-way secure and simultaneous communication using a single channel. Recently, a Measurement Device Independent Quantum Dialogue (MDI-QD) protocol has been proposed (Quantum Information Processing 16.12 (2017): 305). To make the protocol secure against information leakage, the authors have discarded almost half of the qubits remaining after the error estimation phase. We propose two modified versions of the MDI-QD protocol such that the number of discarded qubits is reduced to almost one-fourth of the remaining qubits after the error estimation phase. We use almost half of their discarded qubits along with their used qubits to make our protocol more efficient in qubits count. We show that both of our protocols are secure under the same adversarial model given in MDI-QD protocol.

Ref: International Journal of Quantum Information 18.07 (2020): 2050038.

Biography: Nayana Das is a Ph.D. student at Applied Statistics Unit in Indian Statistical Institute, Kolkata. She received her B.Sc. degree in Mathematics and M.Sc. degree in Pure Mathematics from the University of Calcutta. Her research interest is Quantum Cryptography, Quantum Information Theory and Security.

98.

Name of the Speaker: Pritam chattopadhyay, CSRU, Indian Statistical Institute, Kolkata, India

Title: Thermal Engine from Uncertainty Relation Standpoint

Abstract: The study of thermal devices in the quantum regime has gathered more attraction for research in recent times. Various systems like the quantum amplifier, magnetic refrigerators and engines, semiconductors, thermoelectric generators, and many others explore quantum laws. With the

advent of quantum technology, the exploration of quantum heat engines have gathered more attraction like the Otto engine [1], Stirling engine [2, 3] and so on. Quantum cycles in established heat engines are generally modeled with various quantum systems as working substances. In our

approach, we have considered a heat engine that is modeled with an infinite potential well as the working substance to determine the efficiency and work done with the information of the uncertainty relation of the quantum system [4]. Along with that, the upper and lower bounds on the efficiency of the heat engine are proposed through the uncertainty relation. This work was further extended in the relativistic regime [5] where we have encountered that uncertainty relation has a significant connection with the thermodynamic process.

References:

[1] T. D. Kieu, Phys. Rev. Lett. 93 (2004) 140403.

[2] G. Thomas, D. Das, and S. Ghosh. Phys. Rev. E 100, 012123.

[3] Y. Yin, L. Chen, and F. Wu. The European Physical Journal Plus 132.1 (2017): 1-10.

[4] P. Chattopadhyay et al. Entropy 2021, 23(4), 439.

[5] P. Chattopadhyay, G. Paul, Sci Rep 9, 16967 (2019).