Comment on: `Single-shot simulations of dynamic quantum many-body systems' [arXiv:1501.03224]

TL;DR

This paper critiques a previous study on simulating single-shot measurements in quantum many-body systems, clarifying misconceptions about the complexity of solving the Schrödinger equation and defending phase-space simulation methods.

Contribution

It clarifies the limitations of previous claims regarding the complexity of quantum simulations and defends the validity of phase-space approaches like the truncated Wigner method.

Findings

The Schrödinger equation for many-body systems is exponentially complex to solve exactly.

Phase-space methods can approximate single-shot outcomes in quantum simulations.

Disagreement with claims that single trajectories cannot be interpreted as experimental outcomes.

Abstract

In their recent paper [Nature Physics 15, 451 (2006)], Sakmann and Kasevich study the formation of fringe patterns in ultra-cold Bose gases and claim: `Here, we show how single shots can be simulated from numerical solutions of the time-dependent many-body Schr\"odinger equation.' It would be remarkable if they had solved this exponentially complex equation. Instead they solve nonlinear equations with the aim to approximate the solution of the Schr\"odinger equation. The authors proceed to criticize phase-space approaches to simulating quantum dynamics and claim the impossibility of interpreting single trajectories of the truncated Wigner (tW) method as single-shot experimental outcomes. Here we aim to provide relevant context and elaborate why we disagree with the authors' claims.