Online Seminars on Quantum Information in Poland. Warsaw time zone.

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Past events

Application of probabilistic quantum error correction for general noise

Date: Monday, June 13, 2022
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Passcode: subspace

Speaker: Ryszard Kukulski (IITiS PAN, Gliwice)

Abstract Probabilistic quantum error correction (pQEC) is an error-correcting procedure which uses postselection to determine if the encoded information was successfully restored. In this talk, I will show an application of pQEC for various types of noise channels, e.g. Schur channels, channels with bounded Choi rank and random channels. I will present how to correct errors caused by an arbitrary unitary interaction with an auxiliary qubit system. Finally, I will discuss the optimization problem related with pQEC procedure.

Quantum software in 2022 : patterns and problems

Date: Friday, June 10, 2022
Time: 12:00
Host: ICTQT seminar
Passcode: 46veyQ

Speaker: Ross Duncan (Cambridge Quantum)

Abstract Quantum computers are based on the laws of quantum mechanics rather than Boolean logic; this implies very different algorithmic capabilities and, perhaps more surprisingly, very different issues across the board from software architecture to formal methods. In this talk I’ll give a broad overview of the current state of the art in 2022 and focus on some issues of current interest.

A semidefinite programming hierarchy for the spectral quantum marginal problem

Date: Monday, June 6, 2022
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Passcode: subspace

Speaker: Felix Huber (Jagiellonian University)

Abstract Jensen–Shannon divergence is an important distinguishability measure between probability distributions that finds interesting applications within the context of Information Theory. In particular, this classical divergence belongs to a remarkable class of divergences known as Csiszár or f -divergences. In this talk I analyze the problem of obtaining a distance measure between two quantum states starting from the classical Jensen–Shannon divergence between two probability distributions. Considering the Jensen–Shannon divergence as a Csiszár divergence, I first focus on the problem of distinguishability between two pure quantum states. It is found a quantum version of the classical Jensen–Shannon divergence that differs from the previously introduced Quantum Jensen–Shannon Divergence. The two quantum versions of Jensen–Shannon divergence have different interpretations within the framework of Quantum Information Theory. Whereas the former quantum version of Jensen–Shannon divergence can be interpreted as the Holevo bound, the alternative quantum version obtained in this work equals the accessible information. Furthermore, it is obtained a monoparametric family of metrics between two quantum pure states. Finally, it is presented an extension of this family of metrics to the case of mixed quantum states by means of the concept of purification.

How much information is in a bit?

Date: Wednesday, June 1, 2022
Time: 13:00
Host: Center for Theoretical Physics Colloquium
Passcode: 134595

Speaker: Michał Gańczorz (Google)

Abstract In recent years, the amount of data shared over the internet has increased exponentially. The data formats changed as well. We watch videos and listen to podcasts instead of reading articles. We share images instead of writing messages. But in the end, do we really get more information than before? How much of the data we see is noise? In the seminar, I will talk about formalizing the idea of information, I will show that the information is something we can measure and not just an intangible concept. Finally, I will show how the theory is applied to the several important and practical fields of computer science, such as Data Compression.

Quantum metrics based upon classical Jensen–Shannon divergence

Date: Monday, May 23, 2022
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Passcode: subspace

Speaker: Pedro Lamberti ( Jagiellonian University/ University of Cordoba, Argentina )

Abstract Jensen–Shannon divergence is an important distinguishability measure between probability distributions that finds interesting applications within the context of Information Theory. In particular, this classical divergence belongs to a remarkable class of divergences known as Csiszár or f -divergences. In this talk I analyze the problem of obtaining a distance measure between two quantum states starting from the classical Jensen–Shannon divergence between two probability distributions. Considering the Jensen–Shannon divergence as a Csiszár divergence, I first focus on the problem of distinguishability between two pure quantum states. It is found a quantum version of the classical Jensen–Shannon divergence that differs from the previously introduced Quantum Jensen–Shannon Divergence. The two quantum versions of Jensen–Shannon divergence have different interpretations within the framework of Quantum Information Theory. Whereas the former quantum version of Jensen–Shannon divergence can be interpreted as the Holevo bound, the alternative quantum version obtained in this work equals the accessible information. Furthermore, it is obtained a monoparametric family of metrics between two quantum pure states. Finally, it is presented an extension of this family of metrics to the case of mixed quantum states by means of the concept of purification.

Quantum Gases in Space

Date: Wednesday, May 11, 2022
Time: 12:30
Host: Center for Theoretical Physics Colloquium
Passcode: 134595

Speaker: Naceur Gaaloul

Abstract Atom interferometry for extended drift times promise a major leap in improving precision and accuracy of matter-wave sensors. When taking advantage of the unique space environment for example, fundamental tests challenging the state-of-the-art can be performed using quantum gases systems. The use of cold atoms as a source for such sensors poses however intrinsic challenges mainly linked to the samples size and mixture dynamics in case of dual-atomic tests. In this context, the design of the input states with well-defined initial conditions is required. In this talk, I will report about quantum state engineering methods used to precisely and efficiently control the positions, velocities, expansion rates and squeezing of atomic ensembles in state-of-the-art quantum gas experiments on ground and in space.

Quantifying non-classicality via Local Operations and Shared Randomness

Date: Monday, May 9, 2022
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Passcode: subspace

Speaker: Ana Belen Sainz (University of Gdansk)

Abstract In this talk I will motivate Local Operations and Shared Randomness (LOSR) as a paradigm to quantify non-classical resources, in contrast to Local Operations and Classical Communication (LOCC). I will provide examples of the resource-theoretic study of entanglement, Bell non-classicality, and Einstein-Podolsky-Rosen steering, that stems from this LOSR approach. In particular, I’ll discuss how this triggers a whole distinct new branch of entanglement theory.

Signatures of nonclassicality in quantum mechanical and optical systems

Date: Friday, April 29, 2022
Time: 12:15
Host: IFTIA Seminar (room 361)
Passcode: 78pA05

Speaker: Marcin Markiewicz

Abstract In this talk I will present a brief summary of my habilitation works concerning four aspects of nonclassicality: quantum entanglement, indistinguishability of quantum particles, Bell nonclassicality and contextuality.

Thirty-six entangled officers of Euler: quantum solution of a classically impossible problem

Date: Wednesday, April 27, 2022
Time: 12:30
Host: Center for Theoretical Physics Colloquium
Passcode: 134595

Speaker: Karol Życzkowski (CFT, PAS and Jagiellonian University)

Abstract Classical combinatorial designs are composed of elements of a finite set and arranged with a certain symmetry and balance. A simple example of a combinatorial design is given by a single Latin square: square array of size d filled with d copies of d different symbols, each occurring once in each row and in each column. Such patterns are useful in statistics to design optimal experiments. Analogous collections of quantum states, called a quantum design, determine distinguished quantum measurements and can be applied for various purposes of quantum information processing. Negative solution to the famous problem of 36 officers of Euler implies that there are no two orthogonal Latin squares of order six. We show that the problem has a solution, provided the officers are entangled, and construct orthogonal quantum Latin squares of this size. The solution can be visualized on a chessboard of size six, which shows that 36 officers are split in nine groups, each containing of four entangled states. As a consequence, we find an example of Absolutely Maximally Entangled (AME) state of four subsystems with six levels each, which deserves the appellation golden AME state, as the golden ratio appears prominently in its elements. This state enables us to construct a pure nonadditive quhex quantum error detection code, which allows one to encode a 6-level state into a triplet of such states. Furthermore, using such a state one can teleport any unknown, two-dice quantum state, from any two owners of two subsystems to the lab possessing the two other dice forming the four-dice system. References: [1] S.A Rather, A.Burchardt, W. Bruzda, G. Rajchel-Mieldzioć, A. Lakshminarayan and K. Życzkowski, Thirty-six entangled officers of Euler, Phys. Rev. Lett. 128, 080507 (2022). [2] D. Garisto, Euler’s 243-Year-Old ‘Impossible’ Puzzle Gets a Quantum Solution, Quanta Magazine, Jan. 10, 2022; https://www.quantamagazine.org/ [3] Ph. Ball, A Quantum Solution to an 18th-Century Puzzle, Physics, 15, 29 (2022); https://physics.aps.org/articles/v15/29 [4] K. Życzkowski, W. Bruzda, G. Rajchel-Mieldzioć, A.Burchardt, S.A Rather, A. Lakshminarayan, 9 × 4 = 6 × 6: Understanding the quantum solution to the Euler’s problem of 36 officers, preprint https://arxiv.org/abs/2204.06800

Convex-roof entanglement measures of density matrices block diagonal in disjoint subspaces for the study of thermal states

Date: Monday, April 25, 2022
Time: 14:15
Host: Quantum Chaos and Quantum Information (Jagiellonian University)
Passcode: subspace

Speaker:  Katarzyna Roszak (Institute of Physics, Czech Academy of Sciences)

Abstract We provide a proof that entanglement of any density matrix which block diagonal in subspaces which are disjoint in terms of the Hilbert space of one of the two potentially entangled subsystems can simply be calculated as the weighted average of entanglement present within each block. This is especially useful for thermal-equilibrium states which always inherit the symmetries present in the Hamiltonian, since block-diagonal Hamiltonians are common as are interactions which involve only a single degree of freedom of a greater system. We exemplify our method on a simple Hamiltonian, showing the diversity in possible temperature-dependencies of Gibbs state entanglement which can emerge in different parameter ranges.