Ancilla-assisted probing of temporal quantum correlations of large spins

TL;DR

This paper introduces a measurement protocol that uses spin selection rules and an ancilla to effectively measure temporal quantum correlations in large-spin systems, reducing measurement backaction effects.

Contribution

It proposes a novel protocol leveraging spin selection rules and ancilla coupling to mitigate measurement backaction in temporal quantum correlation measurements for large spins.

Findings

Backaction effects become negligible for large spins with suitable conditions.

The protocol enables probing of Bose-Einstein condensates via light.

Potential application in quantum measurement and quantum information processing.

Abstract

When measuring quantum spins at two or more different times, the later measurements are affected by measurement backaction occurring due to the earlier measurements. This makes the measurement of temporal quantum correlation functions challenging. In this paper, I propose a measurement protocol that mitigates the effect of measurement backaction by exploiting spin selection rules. I show that, under suitable conditions, the effect of measurement backaction on two-time quantum correlations becomes negligible when probing a system consisting of spins with large spin quantum numbers $l\gg s$ by coupling it to a spin-$s$ ancilla degree of freedom. A potential application of such a measurement protocol is the probing of an array of Bose-Einstein condensates by light.