Quantum state reconstruction via continuous measurement

TL;DR

This paper introduces a novel quantum state reconstruction method using weak continuous measurements and Bayesian filtering, enabling non-destructive, real-time state estimation and advancing quantum feedback control capabilities.

Contribution

It develops a continuous measurement-based quantum tomography technique that generalizes traditional methods, allowing for non-destructive, real-time quantum state estimation.

Findings

Enables non-destructive quantum state reconstruction

Provides real-time state estimation with continuous measurement

Facilitates new quantum feedback control strategies

Abstract

We present a new procedure for quantum state reconstruction based on weak continuous measurement of an ensemble average. By applying controlled evolution to the initial state new information is continually mapped onto the measured observable. A Bayesian filter is then used to update the state-estimate in accordance with the measurement record. This generalizes the standard paradigm for quantum tomography based on strong, destructive measurements on separate ensembles. This approach to state estimation can be non-destructive and real-time, giving information about observables whose evolution cannot be described classically, opening the door to new types of quantum feedback control.