**Title & Abstract**

1.

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

2.

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

Title: Counterfactual communication

Abstract: Possibility to communicate between spatially separated regions, without even a single photon passing between the two parties, is an amazing quantum phenomenon. The possibility of transmitting one value of a bit in such a way, the interaction-free measurement, was known for a quarter of a century. The protocols of full communication, including transmitting unknown quantum states were proposed only a few years ago, but it was shown that in all these protocols the particle was leaving a weak trace in the transmission channel, the trace larger than the trace left by a single particle passing through the channel. However, a simple modification of these recent protocols eliminates the trace in the transmission channel and makes all these protocols truly counterfactual.

3.

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.

4.

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:

[1] https://journals.aps.org/pra/abstract/10.1103/PhysRevA.102.052228

[2] https://physics.anu.edu.au/news_events/?NewsID=213

5.

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].

6.

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.

7.

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

8.

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.

9.

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.

10.

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.

11.

Name of the Speaker: Dr. Aikaterini Mandilara

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).

12.

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.

13.

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

14.

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.

15.

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).

16.

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.

17.

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.

18.

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).

19.

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.

20.

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.

21.

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

Title: Light based Hamiltonian simulators

22.

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.

23.

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.

24.

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.

25.

Name of the speaker: Dr.Kavita Dorai

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.

26.

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.

27.

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.

28.

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.

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

Title: Exotic world in the foundations of quantum physics: Precision Experiments and beyond....

31.

Name of the speaker: Dr. Debasis Sarkar

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:

J. Etesse, M. Bouillard, B. Kanseri and R. Tualle-Brouri

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

*Opt. Commun.*380, 148 (2016)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

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

Title: Jaynes-Cummings-model and circuit QED.

44.

Name of the speaker: Manabendra Nath Bera

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.

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

Speaker: Dr. Ayan Khan, Bennett University

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.

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