Calculating the quantum Fisher information via the truncated Wigner method

TL;DR

This paper introduces a novel approach to estimate quantum Fisher information using stochastic phase-space simulations via the Truncated Wigner Approximation, enabling analysis of complex quantum systems.

Contribution

It presents a new method to compute quantum Fisher information from semiclassical samples, extending analysis capabilities to systems modeled by TWA.

Findings

Quantum Fisher information can be computed from TWA samples.

The method works for systems outside the spin-squeezing regime.

It overcomes limitations of the method of moments.

Abstract

In this work, we propose new methods of parameter estimation using stochastic sampling quantum phase-space simulations. We show that it is possible to compute the quantum Fisher information (QFI) from semiclassical stochastic samples using the Truncated Wigner Approximation (TWA). This method extends the class of quantum systems whose fundamental sensitivity limit can be computed efficiently to any system that can be modelled using the TWA, allowing the analysis of more meteorologically useful quantum states. We illustrate this approach with examples, including a system that evolves outside the spin-squeezing regime, where the method of moments fails.