Joint qubit observables induced by indirect measurements in cavity QED

TL;DR

This paper investigates how continuous indirect measurements in cavity QED can induce joint qubit observables, showing that measurement schemes and initial states can tune their properties, with homodyning providing optimal joint measurements.

Contribution

It introduces a framework for understanding time-continuous joint qubit observables induced by indirect measurements in cavity QED, highlighting how measurement type and initial states influence their properties.

Findings

Homodyning orthogonal quadratures yields optimal biased joint observables.

Properties of qubit observables are tunable via measurement scheme and initial cavity state.

Continuous monitoring enables control over quantum measurement incompatibility.

Abstract

A fundamental feature of quantum mechanics is that there are observables which can be measured jointly only when some noise is added to them. Their sharp versions are said to be incompatible. In this work we investigate time-continuous joint qubit observables induced by a indirect time-continuous measurements. In particular we study a paradigmatic situation where a qubit is interacting with a mode of light in a cavity and the light escaping the cavity is continuously monitored. We find that the properties of the qubit observables can be tuned by changing the type of the monitoring scheme or by tuning the initial state of the cavity. We observe that homodyning two orthogonal quadratures produces an optimal pair of biased jointly measurable qubit observables.