Quantum turnstiles for robust measurement of full counting statistics

TL;DR

This paper introduces a scalable quantum protocol using an ancilla turnstile to accurately measure full counting statistics in complex quantum systems, even under noisy conditions, and demonstrates its effectiveness through various examples.

Contribution

The paper presents a novel quantum turnstile protocol that enables robust measurement of FCS from indefinite initial states and noisy dynamics, compatible with tensor-network simulations.

Findings

Successfully measures FCS in a Floquet Heisenberg spin chain

Accurately captures charge transfer in random circuits

Compatible with tensor-network numerical methods

Abstract

We present a scalable protocol for measuring full counting statistics (FCS) in experiments or tensor-network simulations. In this method, an ancilla in the middle of the system acts as a turnstile, with its phase keeping track of the time-integrated particle flux. Unlike quantum gas microscopy, the turnstile protocol faithfully captures FCS starting from number-indefinite initial states or in the presence of noisy dynamics. In addition, by mapping the FCS onto a single-body observable, it allows for stable numerical calculations of FCS using approximate tensor-network methods. We demonstrate the wide-ranging utility of this approach by computing the FCS of the transferred magnetization in a Floquet Heisenberg spin chain, as studied in a recent experiment with superconducting qubits, as well as the FCS of charge transfer in random circuits.