Probing nonclassical light fields with energetic witnesses in waveguide quantum electrodynamics

Maria Maffei,Patrice A Camati,Alexia Auffèves

doi:10.1103/physrevresearch.3.l032073

Abstract

We analyze energy exchanges between a qubit and a resonant field propagating in a waveguide. The joint dynamics is analytically solved within a repeated interaction model. The work received by the qubit is defined as the unitary component of the field-induced energy change. Using the same definition for the field, we show that both work flows compensate each other. Focusing on the charging of a qubit battery by a pulse of light, we evidence that the work provided by a coherent field is an upper bound for the qubit ergotropy, while this bound can be violated by non-classical fields, e.g. a coherent superposition of zero- and single-photon states. Our results provide operational, energy-based witnesses to probe the non-classical nature of a light field.

Highlights

We propose an operational scenario to characterize the nature of energy exchanges between two coupled but otherwise isolated quantum systems
Within this simple partition of the physical world, energy flows split into two components, respectively, stemming from the effective unitary driving that each system performs on one another and from the creation of correlations between the two systems
While entanglement generally hinders local energy extraction, full recovery can be reached at any time provided that the two systems solely exchanged work, which only happens in the limit where one of the systems becomes classical [9]

Summary

Introduction

We propose an operational scenario to characterize the nature of energy exchanges between two coupled but otherwise isolated quantum systems. [4,5], a general framework was proposed to analyze the nature of energy flows between two coupled but otherwise isolated quantum systems. The correlation energy flow), in agreement with the usual definition of work when one of the systems becomes classical and no entanglement appears.

Results

Conclusion