Quantum transition-edge detectors

TL;DR

This paper explores how quantum critical points can be exploited to enhance weak-signal detection, showing that sensitivity can be significantly increased near phase transitions through the Loschmidt echo.

Contribution

It establishes a link between quantum chaos signatures and quantum detection error, demonstrating improved sensitivity near critical points in various models.

Findings

Error probability can be reduced near critical points.

Heisenberg scaling achieved without entanglement or special states.

Applicable to models like quantum Ising, optical parametric oscillator, and Dicke.

Abstract

Small perturbations to systems near critical points of quantum phase transitions can induce drastic changes in the system properties. Here I show that this sensitivity can be exploited for weak-signal detection applications. This is done by relating a widely studied signature of quantum chaos and quantum phase transitions known as the Loschmidt echo to the minimum error probability for a quantum detector and noting that the echo, and therefore the error, can be significantly reduced near a critical point. Three examples, namely, the quantum Ising model, the optical parametric oscillator model, and the Dicke model, are presented to illustrate the concept. For the latter two examples, the detectable perturbation can exhibit a Heisenberg scaling with respect to the number of detectors, even though the detectors are not entangled and no special quantum state preparation is specified.