Dynamics revealed by correlations of time-distributed weak measurements of a single spin

TL;DR

This paper demonstrates that analyzing correlations in time-distributed weak measurements of a single spin can reveal detailed quantum dynamics and decoherence effects without traditional control methods.

Contribution

It introduces a novel approach using correlation analysis of weak measurements to study quantum spin dynamics and decoherence, avoiding invasive control techniques.

Findings

Third order correlations reveal true spin decoherence

Weak measurements minimally disturb the system

Correlation analysis distinguishes inhomogeneous broadening effects

Abstract

We show that the correlations in stochastic outputs of time-distributed weak measurements can be used to study the dynamics of an individual quantum object, with a proof-of-principle setup based on small Faraday rotation caused by a single spin in a quantum dot. In particular, the third order correlation can reveal the "true" spin decoherence, which would otherwise be concealed by the inhomogeneous broadening effect in the second order correlations. The viability of such approaches lies in that (1) in weak measurement the state collapse which would disturb the system dynamics occurs at a very low probability, and (2) a shot of measurement projecting the quantum object to a known basis state serves as a starter or stopper of the evolution without pumping or coherently controlling the system as otherwise required in conventional spin echo.