Coherent Averaging

TL;DR

This paper analyzes a coherent averaging scheme in quantum metrology, showing how measuring a quantum bus can achieve Heisenberg-limited sensitivity, with detailed insights into factors affecting performance.

Contribution

It provides a comprehensive analysis of the coherent averaging scheme, combining analytical and numerical methods to understand its potential for quantum parameter estimation.

Findings

Achieves Heisenberg-limited sensitivity in parameter measurement.

Sensitivity scaling depends on initial state, interaction strength, and measurement choice.

Provides detailed theoretical and numerical characterization of the scheme.

Abstract

We investigate in detail a recently introduced "coherent averaging scheme" in terms of its usefulness for achieving Heisenberg limited sensitivity in the measurement of different parameters. In the scheme, $N$ quantum probes in a product state interact with a quantum bus. Instead of measuring the probes directly and then averaging as in classical averaging, one measures the quantum bus or the entire system and tries to estimate the parameters from these measurement results. Combining analytical results from perturbation theory and an exactly solvable dephasing model with numerical simulations, we draw a detailed picture of the scaling of the best achievable sensitivity with $N$, the dependence on the initial state, the interaction strength, the part of the system measured, and the parameter under investigation.