Probing quantum and thermal noise in an interacting many-body system

TL;DR

This paper experimentally investigates quantum and thermal noise in one-dimensional Bose condensates, revealing a crossover from thermal to quantum noise and observing quantum fluctuations and quasi long-range order.

Contribution

It provides the first experimental analysis of the full quantum noise distribution in an interacting many-body system and observes quantum fluctuations in 1D atomic condensates.

Findings

Observed crossover from thermal to quantum noise in Bose condensates.

First experimental detection of quasi long-range order in 1D atomic systems.

Analyzed full distribution of quantum noise, matching theoretical predictions.

Abstract

The probabilistic character of the measurement process is one of the most puzzling and fascinating aspects of quantum mechanics. In many-body systems quantum mechanical noise reveals non-local correlations of the underlying many-body states. Here, we provide a complete experimental analysis of the shot-to-shot variations of interference fringe contrast for pairs of independently created one-dimensional Bose condensates. Analyzing different system sizes we observe the crossover from thermal to quantum noise, reflected in a characteristic change in the distribution functions from Poissonian to Gumbel-type, in excellent agreement with theoretical predictions based on the Luttinger liquid formalism. We present the first experimental observation of quasi long-range order in one-dimensional atomic condensates, which is a hallmark of quantum fluctuations in one-dimensional systems. Furthermore, our experiments constitute the first analysis of the full distribution of quantum noise in an interacting many-body system.