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Thermal counting statistics in an atomic two-mode squeezed vacuum state

by M. Perrier, Z. Amodjee, P. Dussarrat, A. Dareau, A. Aspect, M. Cheneau, D. Boiron, C. I. Westbrook

Submission summary

As Contributors: Marc Cheneau · Alexandre Dareau · Christoph Westbrook
Arxiv Link: https://arxiv.org/abs/1904.04135v1
Date submitted: 2019-04-09
Submitted by: Westbrook, Christoph
Submitted to: SciPost Physics
Domain(s): Experimental
Subject area: Atomic, Molecular and Optical Physics - Experiment

Abstract

We measure the population distribution in one of the atomic twin beams generated by four-wave mixing in an optical lattice. Although the produced two-mode squeezed state is pure, each individual mode is described as a statistical mixture. We confirm the prediction that the particle number follows an exponential distribution when only one spatio-temporal mode is selected. We also show that this distribution accounts well for the contrast of an atomic Hong--Ou--Mandel experiment.

Current status:
Editor-in-charge assigned

Submission & Refereeing History

Submission 1904.04135v1 on 9 April 2019

Reports on this Submission

Anonymous Report 1 on 2019-5-3 Invited Report

Strengths

1 - Very clear and well written manuscript with appropriate figures.
2 - Basic theory is outlined sufficiently.

Weaknesses

1 - Novelty of results is not made clear.

Report

Perrier et. al. present an investigation of four-wave mixing in an optical lattice, specifically focused on characterizing the dynamically produced state as a two-mode squeezed vacuum. The main result is the measurement of the single-mode distribution function P(n) of the mode population n, which they demonstrate is consistent with the thermal distribution predicted by the entangled two-mode squeezed state. They also present data from an atomic Hong-Ou-Mandel experiment (which they previously demonstrated elsewhere) and show that the visibility of the HOM `dip' is consistent with a simple model which assumes a two-mode squeezed vacuum as the input state and is thus characterized solely by the mean mode occupation <n>.

I have a few comments regarding the material in the paper. Overall, I find the paper is not clear in establishing what they regard as novel here. Specifically, whilst atomic four-wave mixing experiments are ideal to study P(n) (due to, e.g., the typically larger mode occupation compared to quantum optics experiments), this result has already been published for a two-mode squeezed vacuum in another atom-optics setup in arXiv:1807.07504 (as they note in the manuscript). Perhaps the authors might comment on whether there is a particular (in principle) advantage to the platform presented here: For example, does the tunability of the mode population in the optical lattice setup mean it might be easier to study the distribution P(n) beyond the undepleted pump regime presented here?

Further to this, I wonder if the authors could comment on whether there is the possibility of extracting further data to support their conclusion that the source state is indeed a two-mode squeezed vacuum. In particular, given the ability to extract histograms P(n) for a single mode (with additional averaging), is it possible to investigate the two-mode distribution P(n_1 + n_2) and observe evidence of an odd-even oscillatory behavior?

Overall, the paper is well written and the included results are discussed sufficiently. However, I would like the authors to respond to these points before I make a recommendation for publication.

Requested changes

1 - The authors should cite Phys. Rev. Lett. 118, 240402 (2017) as well as Ref. 19. Here, the same group reports characterization of 3rd and 4th order correlations which are consistent with a two-mode squeezed vacuum source.

2 - The authors should give an estimate of the total depletion of the condensate. I understand that the experimental details can be found in previous publications, but the case for the resulting state being two-mode squeezed vacuum is based on the undepleted pump assumption!

3 - The observed and predicted visibility for this work are only just in agreement due to the error bars (attributed to fitting) in Table 1. Perhaps the authors could give a rough estimate of what additional sources of error (e.g., technical noise due to imperfect beam-splitters etc) might contribute so the result can be viewed with more confidence.

  • validity: high
  • significance: low
  • originality: low
  • clarity: high
  • formatting: excellent
  • grammar: perfect

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