The ICTP South-American Institute for Fundamental Research hosted at the IFT-UNESP brings to you the Quantum Physics Journal Club, a weekly meeting dedicated to discussing the latest papers and findings in the broad area of quantum physics (for example quantum matter, quantum chaos, or quantum information and quantum technologies). We will also host seminars by members of our community or visitors. Our meetings will be held in person on Mondays, starting at 4 pm, São Paulo Time.
Everyone is welcome to attend!
William Estrada (IFT-UNESP): Real Randomized Benchmarking
In this talk, we will review the results presented in the following paper
https://quantum-journal.org/papers/q-2018-08-22-85/
Concretely, I will provide an introduction to simple integrals over the orthogonal/unitary groups, and their applications in quantum information processing.
10/June/2024: Dario Rosa (ICTP-SAIFR and IFT-UNESP)
Random Free Fermions: An Analytical Example of Eigenstate Thermalization
In this talk, we will review the results, based on random Matrix Theory and derived in this paper
https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.116.030401
on the validity of the Eigenstate Thermalization Hypothesis for free fermionic systems, when evaluated in the multiparticle sector.
27/May/2024: Washington F. dos Santos (IFT-UNESP)
Emergent incoherent current due to the presence of electron-electron interaction in single-electron transistor
In this work, we simulate a single-electron transistor composed of a segment of a graphene nanoribbon coupled to carbon nanotubes electrodes. To describe the system we consider the electron-electron interaction in molecular orbitals combined with the methods of the recursive tight-binding Green's function, Anderson impurity model, non-crossing approximation and the generalization Fisher-Lee Transmission. Using this methodology we are able to recover the experimentally observed phenomena, such as the Colombian blockade, as well as the corresponding Coulomb diamonds. In order to deal more realistically for the theoretical approach to nanodevices where the electron-electron interaction cannot be neglected along with the emergence of decoherence phenomena due to the presence of the interaction. In particular, we look at the incoherent transport, and we see that it describes an essential part of the phenomena we observed earlier and that this term cannot be neglected, due to the emergence of purely incoherent electronic current.
06/May/2024: Francisco José Divi (IFT-UNESP)
A Hamiltonian Approach to the Anderson Problem with Correlated Disorder in 1D
In this journal we will introduce a simple approach to the Anderson problem with (un)correlated disorder in 1D. By mapping the problem to a classical stochastic system, we will compute localization lengths based on classical trajectories. Then, we will discuss whether different types of disorder can destroy localization in 1D. This talk aims to be pedagogical and no background is needed.
All the results are based on this review: https://www.sciencedirect.com/science/article/pii/S0370157311002936.
29/April/2024: Rui Aquino (ICTP-SAIFR and IFT-UNESP)
Critical and non-critical non-Hermitian topological phase transitions in one-dimensional chains
In this work we investigate non-Hermitian topological phase transitions using real-space edge states as a paradigmatic tool. We focus on the simplest non-Hermitian variant of the Su-Schrieffer-Hegger model, including a parameter that denotes the degree of non-hermiticity of the system. We study the behavior of the zero energy edge states at the non-trivial topological phases with integer and semi-integer topological winding number, according to the distance to the critical point. We obtain that depending on the parameters of the model the edge states may penetrate into the bulk, as expected in Hermitian topological phase transitions. We also show that, using the topological characterization of the exceptional points, we can describe the intricate chiral behavior of the edge states across the whole phase diagram. Moreover, we characterize the criticality of the model by determining the correlation length critical exponent, directly from numerical calculations of the penetration length of the zero modes edge states.