Below you will find a list of seminars organised by ICTQT.
For quantum events at other institutions in Poland please see the KCIK website.
Speaker: M.Hopjan (J. Stefan Institute, Ljubljana)
Abstract
Recently it was shown, in the three-dimensional Anderson model [1] and the avalanche model of ergodicity breaking transitions [2], that the spectral form factor and the Thouless time extracted from the spectral form factor are scale invariant quantities at eigenstate transition. Thus they represent useful measures for characterisation of eigenstate transition. In the literature, an alternative definition of the Thouless time was given in terms of survival probability [3,4] which measure the stability of an initial state. Motivated by this fact, we investigate the survival probability measure and possible connections to the spectral form factor measure.
We focus on differences in behavior of the survival probability across the eigenstate transitions. Remarkably, we observe scaling invariant power-law decay of the survival probability at the transition in three physically relevant models: the three-dimensional Anderson model, one-dimensional Aubry-Andre model, and the avalanche model of ergodicity breaking transitions. We discuss connections of this universality to the universality of the spectral form factor measure. Our study [5] demonstrate that both quantities, the survival probability and the spectral form factor, are useful tool for detection of the eigenstate transitions.
[1] J. Šuntajs, T. Prosen and L. Vidmar, Annals of Physics 435, 168469 (2021)
[2] J. Šuntajs and L. Vidmar, Phys. Rev. Lett. 129, 060602 (2022)
[3] M. Schiulaz, E. J. Torres-Herrera, and L. F. Santos, Phys. Rev. B 99, 174313 (2019)
[4] T. L. M. Lezama, E. J. Torres-Herrera, F. Pérez-Bernal, Y. Bar Lev, and L. F. Santos, Phys. Rev. B 104, 085117 (2021)
[5] M. Hopjan and L. Vidmar, ArXiv:2212.13888
Speaker: Ravishankar Ramanathan (Hong Kong)
Abstract
Abstract: It is well known that classical tools do not allow the extraction of randomness from a single random source. On the other hand, quantum theory allows for such extraction even within the device-independent framework. While practically feasible protocols have been proposed for randomness sources that possess a specific Santha-Vazirani structure, it has remained an open problem to derive a finite-device protocol for extraction from an arbitrary min-entropy source. In this talk, we will present and outline the security of such a device-independent protocol with the following features: (1) robust amplification of an arbitrary min-entropy source, (2) usage of a device with a constant number of components, (3) security in the presence of a quantum adversary.Speaker: Adam Sawicki (CFT PAN, Warsaw)
Abstract
Universal quantum gates play a central role in quantum computing. It is well known that in order to construct a universal set of gates for many qudits it is enough to take a universal set for one qudit and extend it by a two-qudit entangling gate. On the other hand, it is a great challenge to find a time efficient procedure that enables deciding if a given set of one-qudit gates is universal. In this talk I will connect the universality problem with the theory of t-designs and provide a universality checking procedure whose complexity scales polynomially with the dimension of the qudit. The talk will be based on: A. Sawicki, L. Mattioli, Z. Zimboras Phys. Rev. A 105, 052602, 2022Speaker: Luis Pedro Garcia Pintos (Joint Quantum Institute and QuICS, University of Maryland)
Abstract
I will give an overview of recent bounds on the speed with which observables can evolve in quantum and classical systems. The bounds typically take the form of uncertainty relations that connect the maximum rate of change of an observable to its standard deviation. Surprisingly, these general bounds are saturated in a range of disciplines. I will illustrate this with an application of these techniques to quantum annealing.Speaker: Ingo Roth (Quantum research centre, Technology Innovation Institute, Abu Dhabi, UAE)
Abstract
Randomized benchmarking protocols have become the prominent tool for assessing the quality of gates on digital quantum computing platforms. In `classical’ variants of randomized benchmarking multi-qubit gates are drawn uniformly from a finite group. The functioning of such schemes can be rigorous guaranteed under realistic assumptions. In contrast, experimentally attractive and practically more scalable randomized benchmarking schemes often directly perform random circuits or use other non-uniform probability measures. An important example for such a non-uniform protocol is linear cross-entropy benchmarking. The theoretical understanding of non-uniform randomized benchmarking is still an ongoing effort. We present a new extension of general theoretical guarantees for randomized benchmarking to non-uniform measures. Combined with results on random walks, our results identify experimental parameter regimes where one can guarantee non-uniform randomized benchmarking protocols to work reliably. On the technical side, we develop a general perturbative description of noise in random circuits in terms of harmonic analysis that can also be used to analyze the noise-robustness of random circuit protocols beyond RB.Speaker: Paweł Horodecki (Gdansk)
Programme
15.30 – 15:55 Andrzej Jamiołkowski “My memories of Roman Stanisław Ingarden”.
16:00 – 16:55 2022 Ingarden Memorial Lecture
Peter Shor: “The development of quantum error correcting codes”
17:00 – 17:15 coffee break
17:15-17:45 Awarding of Junior KCIK Award for best Bachelor Thesis in quantum Information, talk of the winner
17:45-18:15 Distinguished talk
18:18 The End