Experimental validation of the Kibble-Zurek mechanism on a digital quantum computer

Abstract

The Kibble-Zurek mechanism (KZM) captures the essential physics of nonequilibrium quantum phase transitions with symmetry breaking. KZM predicts a universal scaling power law for the defect density which is fully determined by the system’s critical exponents at equilibrium and the quenching rate. We experimentally tested the KZM for the simplest quantum case, a single qubit under the Landau-Zener evolution, on an open access IBM quantum computer (IBM-Q). We find that for this simple one-qubit model, experimental data validates the central KZM assumption of the adiabatic-impulse approximation for a well isolated qubit. Furthermore, we report on extensive IBM-Q experiments on individual qubits embedded in different circuit environments and topologies, separately elucidating the role of crosstalk between qubits and the increasing decoherence effects associated with the quantum circuit depth on the KZM predictions. Our results strongly suggest that increasing circuit depth acts as a decoherence source, producing a rapid deviation of experimental data from theoretical unitary predictions.

Observation of partial and infinite-temperature thermalization induced by repeated measurements on a quantum hardware

“…Thus, they can validate a large number of theoretical results, which were not (or very little) corroborated so far. In the last years, among these, a plethora of studies has been conducted on such devices [40][41][42][43][44][45][46][47][48][49][50][51]. In particular, in the context of quantum thermodynamics, several experiments have been performed on quantum hardware to benchmark quantum fluctuation relations [52,53], to test their robustness against intermediate projective measurements [22], and to experimentally realize [52,[54][55][56][57] quantum heat engines and refrigerators [58][59][60][61][62].…”