Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Detecting correlations in condensates

Christoph Ira Westbrook

Published Feb 2, 2009• 0 citations
OpenAlex

Abstract

In our laboratory, we have been developing measurement methods to extract at two-particle correlations functions in degenerate gases. Simple examples include the observation of correlated atom pairs in a four wave mixing geometry, and Hanbury Brown-Twiss type interferometry. In these experiments we observe the correlations in momentum space. We have also been able to observe density fluctuations in position space by using in situ imaging on an atom chip. I will attempt to review some of the possibilities open to us and discuss some of our plans for the immediate future.

Related papers

Measuring two particle correlation functions

Christoph Ira Westbrook

This talk discusses two types of measurements on two particle correlations in a Bose-Einstein condensate. In one apparatus we perform the analog of the famous Hanbury-Brown Twiss experiment to investigate correlations in momentum space. In a second experiments we use insitu measurements of atom clouds on a chip to obtain measuremnents of density fluctuations.

•Jun 16, 2008•0 citations

Producing and Detecting Correlated Atoms

Christoph Ira Westbrook, M. Schellekens, A. Perrin +12 more

We discuss experiments to produce and detect atom correlations in a degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic analog of the celebrated Hanbury Brown Twiss experiment, in which atom correlations result simply from interference effects without any atom interactions. We have performed this experiment for both bosons and fermions. Next we show how atom interactions produce correlated atoms using the atomic analog of spontaneous four‐wave mixing. Finally, we briefly mention experiments on a one dimensional gas on an atom chip in which correlation effects due to both interference and interactions have been observed.

arXiv:quant-ph/0609019•AIP conference proceedings•Jan 1, 2006•2 citations

Single-site- and single-atom-resolved measurement of correlation functions

Manuel Endres, Marc Cheneau, Takeshi Fukuhara +8 more

Correlation functions play an important role for the theoretical and experimental characterization of many-body systems. In solid-state systems, they are usually determined through scattering experiments, whereas in cold gases systems, time-of-flight, and in situ absorption imaging are the standard observation techniques. However, none of these methods allow the in situ detection of spatially resolved correlation functions at the single-particle level. Here, we give a more detailed account of recent advances in the detection of correlation functions using in situ fluorescence imaging of ultracold bosonic atoms in an optical lattice. This method yields single-site- and single-atom-resolved images of the lattice gas in a single experimental run, thus gaining direct access to fluctuations in the many-body system. As a consequence, the detection of correlation functions between an arbitrary set of lattice sites is possible. This enables not only the detection of two-site correlation functions but also the evaluation of non-local correlations, which originate from an extended region of the system and are used for the characterization of quantum phases that do not possess (quasi-)long-range order in the traditional sense.

•Oct 1, 2013•34 citations

Two experiments on quantum correlations in gases of metastable helium: fermion antibunching and a study of boson pair correlations in the collision of two condensates

Valentina Krachmalnicoff

This thesis presents two experiments on ultracold gases of metastable Helium that constitute the extension, to matter waves, of experiments that have been fundamental for the development of quantum optics. Both experiments have been realized by using a single atom detector, that allows one to reconstruct the position of the atoms in three dimensions. In the first experiment we directly compared the two-body correlation function for a cold cloud of identical fermions and for a cold cloud of identical bosons at the same temperature issued from the same experimental apparatus. Since bosons and fermions obey different quantum statistics, the two-body correlation functions are different: identical bosons tend to be detected bunched in pairs, while identical fermions tend to antibunch because of the Pauli exclusion principle. In the second experiment we studied the correlation between pairs of bosonic atoms generated in the collision of two Bose-Einstein condensates. The measurement of the correlation function allows us to demonstrate that atoms flying back to back in the centre of mass frame are correlated in pairs. Furthermore the observation of a Hanbury Brown Twiss correlation between atoms with collinear velocity demonstrates that our system cannot be interpreted in terms of classical mechanics, but that the bosonic statistics plays a crucial role. A new version of the experiment will allow us to measure the angular dependence of the population of the scattering modes and the number difference squeezing between two correlated modes.

•Jun 22, 2009•1 citation

The Observation of Matter Wave Fluctuations

P. L. Knight

In the 1950s, Hanbury Brown and Twiss developed a novel way to measure the size of stars by studying the coherence of the light they emit. These intensity correlations, at the time obtained from an incoherent thermal source of radiation, were the source of confusion at first but ended up initiating an entire new field of physics: the discipline of quantum optics. In his Perspective, [Knight][1] discusses results reported in the same issue by [ Schellekens et al. ][2] in which these same correlation effects have been seen in cold atomic gases, giving rise to intensity correlations of matter waves. The findings suggest a host of new opportunities in this field of quantum atom optics. [1]: http://www.sciencemag.org/cgi/content/full/310/5748/631 [2]: http://www.sciencemag.org/cgi/content/short/310/5748/648

Science•Oct 27, 2005•8 citations

Interference and correlations

C. J. Pethick, H. Smith

Bose–Einstein condensates of particles behave in many ways like coherent radiation fields, and the realization of Bose–Einstein condensation in dilute gases has opened up the experimental study of interactions between coherent matter waves. In addition, the existence of these dilute trapped quantum gases has prompted a re-examination of a number of theoretical issues. In Sec. 13.1 we discuss Josephson tunnelling of a condensate between two wells and the role of fluctuations in particle number and phase. The number and phase variables play a key role in the description of the classic interference experiment, in which two clouds of atoms are allowed to expand and overlap (Sec. 13.2). Rather surprisingly, an interference pattern is produced even though initially the two clouds are completely isolated. Density fluctuations in a Bose gas are studied in Sec. 13.3, where we relate atomic clock shifts to the two-particle correlation function. The ability to manipulate gaseous Bose–Einstein condensates by lasers has made possible the study of coherent matter wave optics and in Sec. 13.4 we describe applications of these techniques to observe solitons, Bragg scattering, and non-linear mixing of matter waves. How to characterize Bose–Einstein condensation in terms of the density matrix is the subject of Sec. 13.5, where we also consider fragmented condensates.

Cambridge University Press eBooks•Sep 11, 2008•0 citations
In our laboratory, we have been developing measurement methods to extract at two-particle correlations functions in degenerate gases. Simple examples include the observation of correlated atom pairs in a four wave mixing geometry, and Hanbury Brown-Twiss type interferometry. In these experiments we observe the correlations in momentum space. We have also been able to observe density fluctuations in position space by using in situ imaging on an atom chip. I will attempt to review some of the possibilities open to us and discuss some of our plans for the immediate future.
We discuss experiments to produce and detect atom correlations in a degenerate or nearly degenerate gas of neutral atoms. First we treat the atomic analog of the celebrated Hanbury Brown Twiss experiment, in which atom correlations result simply from interference effects without any atom interactions. We have performed this experiment for both bosons and fermions. Next we show how atom interactions produce correlated atoms using the atomic analog of spontaneous four‐wave mixing. Finally, we briefly mention experiments on a one dimensional gas on an atom chip in which correlation effects due to both interference and interactions have been observed.
Correlation functions play an important role for the theoretical and experimental characterization of many-body systems. In solid-state systems, they are usually determined through scattering experiments, whereas in cold gases systems, time-of-flight, and in situ absorption imaging are the standard observation techniques. However, none of these methods allow the in situ detection of spatially resolved correlation functions at the single-particle level. Here, we give a more detailed account of recent advances in the detection of correlation functions using in situ fluorescence imaging of ultracold bosonic atoms in an optical lattice. This method yields single-site- and single-atom-resolved images of the lattice gas in a single experimental run, thus gaining direct access to fluctuations in the many-body system. As a consequence, the detection of correlation functions between an arbitrary set of lattice sites is possible. This enables not only the detection of two-site correlation functions but also the evaluation of non-local correlations, which originate from an extended region of the system and are used for the characterization of quantum phases that do not possess (quasi-)long-range order in the traditional sense.
This thesis presents two experiments on ultracold gases of metastable Helium that constitute the extension, to matter waves, of experiments that have been fundamental for the development of quantum optics. Both experiments have been realized by using a single atom detector, that allows one to reconstruct the position of the atoms in three dimensions. In the first experiment we directly compared the two-body correlation function for a cold cloud of identical fermions and for a cold cloud of identical bosons at the same temperature issued from the same experimental apparatus. Since bosons and fermions obey different quantum statistics, the two-body correlation functions are different: identical bosons tend to be detected bunched in pairs, while identical fermions tend to antibunch because of the Pauli exclusion principle. In the second experiment we studied the correlation between pairs of bosonic atoms generated in the collision of two Bose-Einstein condensates. The measurement of the correlation function allows us to demonstrate that atoms flying back to back in the centre of mass frame are correlated in pairs. Furthermore the observation of a Hanbury Brown Twiss correlation between atoms with collinear velocity demonstrates that our system cannot be interpreted in terms of classical mechanics, but that the bosonic statistics plays a crucial role. A new version of the experiment will allow us to measure the angular dependence of the population of the scattering modes and the number difference squeezing between two correlated modes.
In the 1950s, Hanbury Brown and Twiss developed a novel way to measure the size of stars by studying the coherence of the light they emit. These intensity correlations, at the time obtained from an incoherent thermal source of radiation, were the source of confusion at first but ended up initiating an entire new field of physics: the discipline of quantum optics. In his Perspective, [Knight][1] discusses results reported in the same issue by [ Schellekens et al. ][2] in which these same correlation effects have been seen in cold atomic gases, giving rise to intensity correlations of matter waves. The findings suggest a host of new opportunities in this field of quantum atom optics. [1]: http://www.sciencemag.org/cgi/content/full/310/5748/631 [2]: http://www.sciencemag.org/cgi/content/short/310/5748/648
Bose–Einstein condensates of particles behave in many ways like coherent radiation fields, and the realization of Bose–Einstein condensation in dilute gases has opened up the experimental study of interactions between coherent matter waves. In addition, the existence of these dilute trapped quantum gases has prompted a re-examination of a number of theoretical issues. In Sec. 13.1 we discuss Josephson tunnelling of a condensate between two wells and the role of fluctuations in particle number and phase. The number and phase variables play a key role in the description of the classic interference experiment, in which two clouds of atoms are allowed to expand and overlap (Sec. 13.2). Rather surprisingly, an interference pattern is produced even though initially the two clouds are completely isolated. Density fluctuations in a Bose gas are studied in Sec. 13.3, where we relate atomic clock shifts to the two-particle correlation function. The ability to manipulate gaseous Bose–Einstein condensates by lasers has made possible the study of coherent matter wave optics and in Sec. 13.4 we describe applications of these techniques to observe solitons, Bragg scattering, and non-linear mixing of matter waves. How to characterize Bose–Einstein condensation in terms of the density matrix is the subject of Sec. 13.5, where we also consider fragmented condensates.