TY - RPRT T1 - Data Needs and Challenges of Quantum Dot Devices Automation: Workshop Report Y1 - 2023 A1 - Justyna P. Zwolak A1 - Jacob M. Taylor A1 - Reed Andrews A1 - Jared Benson A1 - Garnett Bryant A1 - Donovan Buterakos A1 - Anasua Chatterjee A1 - Sankar Das Sarma A1 - Mark A. Eriksson A1 - Eliška Greplová A1 - Michael J. Gullans A1 - Fabian Hader A1 - Tyler J. Kovach A1 - Pranav S. Mundada A1 - Mick Ramsey A1 - Torbjoern Rasmussen A1 - Brandon Severin A1 - Anthony Sigillito A1 - Brennan Undseth A1 - Brian Weber AB -

Gate-defined quantum dots are a promising candidate system to realize scalable, coupled qubit systems and serve as a fundamental building block for quantum computers. However, present-day quantum dot devices suffer from imperfections that must be accounted for, which hinders the characterization, tuning, and operation process. Moreover, with an increasing number of quantum dot qubits, the relevant parameter space grows sufficiently to make heuristic control infeasible. Thus, it is imperative that reliable and scalable autonomous tuning approaches are developed. In this report, we outline current challenges in automating quantum dot device tuning and operation with a particular focus on datasets, benchmarking, and standardization. We also present ideas put forward by the quantum dot community on how to overcome them.

UR - https://arxiv.org/abs/2312.14322 U5 - https://doi.org/10.48550/arXiv.2312.14322 ER - TY - JOUR T1 - Euler-obstructed Cooper pairing: Nodal superconductivity and hinge Majorana zero modes JF - Physical Review B Y1 - 2022 A1 - Jiabin Yu A1 - Yu-An Chen A1 - Sankar Das Sarma AB -

Since the proposal of monopole Cooper pairing in [Phys. Rev. Lett. 120, 067003 (2018)], considerable research efforts have been dedicated to the study of Cooper pairing order parameters constrained (or obstructed) by the nontrivial normal-state band topology at Fermi surfaces in 3D systems. In the current work, we generalize the topologically obstructed pairings between Chern states (like the monopole Cooper pairing) by proposing Euler obstructed Cooper pairing in 3D systems. The Euler obstructed Cooper pairing widely exists between two Fermi surfaces with nontrivial band topology characterized by nonzero Euler numbers; such Fermi surfaces can exist in 3D PT-protected spinless-Dirac/nodal-line semimetals with negligible spin-orbit coupling, where PT is the space-time inversion symmetry. An Euler obstructed pairing channel must have pairing nodes on the pairing-relevant Fermi surfaces, and the total winding number of the pairing nodes is determined by the sum or difference of the Euler numbers on the Fermi surfaces. In particular, we find that when the normal state is time-reversal invariant and the pairing is weak, a sufficiently-dominant Euler obstructed pairing channel with zero total momentum leads to nodal superconductivity. If the Fermi surface splitting is small, the resultant nodal superconductor hosts hinge Majorana zero modes. The possible dominance of the Euler obstructed pairing channel near the superconducting transition and the robustness of the hinge Majorana zero modes against disorder are explicitly demonstrated using effective or tight-binding models. Our work presents the first class of higher-order nodal superconductivity originating from the topologically obstructed Cooper pairing.

VL - 105 UR - https://arxiv.org/abs/2109.02685 U5 - https://doi.org/10.1103%2Fphysrevb.105.104515 ER - TY - JOUR T1 - Butterfly effect in interacting Aubry-Andre model: thermalization, slow scrambling, and many-body localization Y1 - 2019 A1 - Shenglong Xu A1 - Xiao Li A1 - Yi-Ting Hsu A1 - Brian Swingle A1 - Sankar Das Sarma AB -

The many-body localization transition in quasiperiodic systems has been extensively studied in recent ultracold atom experiments. At intermediate quasiperiodic potential strength, a surprising Griffiths-like regime with slow dynamics appears in the absence of random disorder and mobility edges. In this work, we study the interacting Aubry-Andre model, a prototype quasiperiodic system, as a function of incommensurate potential strength using a novel dynamical measure, information scrambling, in a large system of 200 lattice sites. Between the thermal phase and the many-body localized phase, we find an intermediate dynamical phase where the butterfly velocity is zero and information spreads in space as a power-law in time. This is in contrast to the ballistic spreading in the thermal phase and logarithmic spreading in the localized phase. We further investigate the entanglement structure of the many-body eigenstates in the intermediate phase and find strong fluctuations in eigenstate entanglement entropy within a given energy window, which is inconsistent with the eigenstate thermalization hypothesis. Machine-learning on the entanglement spectrum also reaches the same conclusion. Our large-scale simulations suggest that the intermediate phase with vanishing butterfly velocity could be responsible for the slow dynamics seen in recent experiments.

UR - https://arxiv.org/abs/1902.07199 ER -