The Transition from Quantum to Classical in weak measurements and reconstruction of Quantum Correlation

TL;DR

This paper investigates the transition from quantum to classical behavior in weak measurements, demonstrating how to reconstruct quantum correlations and validate the approach through experimental violations of the Leggett-Garg inequality.

Contribution

It introduces a method to relate measurement strength to quantum dynamics in a single system and validates this with experimental data.

Findings

Relation between readout signal and quantum dynamics established

Measurement strength determined experimentally

Violations of Leggett-Garg inequality confirmed

Abstract

The ability to follow the dynamics of a quantum system in a quantitative manner is of key importance for quantum technology. Despite its central role, justifiable deduction of the quantum dynamics of a single quantum system in terms of a macroscopical observable remains a challenge. Here we show that the relation between the readout signal of a single electron spin and the quantum dynamics of the single nuclear spin is given by a parameter related to the measurement strength. We determine this measurement strength in independent experiments and use this value to compare our analysis of the quantum dynamics with experimental results. We prove the validity of our approach by measuring violations of the Leggett-Garg inequality.