Quantum Noise as an Entanglement Meter

TL;DR

This paper establishes a universal relation between entanglement entropy and current fluctuations in a quantum point contact, enabling experimental measurement of entanglement in many-body quantum systems.

Contribution

It introduces a novel method to measure entanglement entropy directly through current noise in quantum point contacts, linking theoretical predictions with experimental observables.

Findings

Derived a universal relation between entanglement entropy and current fluctuations.

Connected electric noise in QPCs with conformal field theory predictions.

Proposed a feasible experimental approach to measure entanglement entropy.

Abstract

Entanglement entropy, which is a measure of quantum correlations between separate parts of a many-body system, has emerged recently as a fundamental quantity in broad areas of theoretical physics, from cosmology and field theory to condensed matter theory and quantum information. The universal appeal of the entanglement entropy concept is related, in part, to the fact that it is defined solely in terms of the many-body density matrix of the system, with no relation to any particular observables. However, for the same reason, it has not been clear how to access this quantity experimentally. Here we derive a universal relation between entanglement entropy and the fluctuations of current flowing through a quantum point contact (QPC) which opens a way to perform a direct measurement of entanglement entropy. In particular, by utilizing space-time duality of 1d systems, we relate electric noise generated by opening and closing the QPC periodically in time with the seminal S = 1/3 log L prediction of conformal field theory.