Correlations in Amplified Four-Wave Mixing of Matter Waves

RuGway, Wu; Hodgman, Sean; Dall, Robert; Johnsson, Mattias; Truscott, A. G.

doi:10.1103/physrevlett.107.075301

Cited by 24 publications

(25 citation statements)

References 29 publications

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“…It has been predicted [13,14,46] that the modes propagating in opposite direction are entangled, similar to those produced in atomic four wave mixing [47][48][49]. A similar measurement technique should be able to reveal them.…”

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confidence: 99%

Second-order coherence of superradiance from a Bose-Einstein condensate

et al. 2014

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We have measured the 2-particle correlation function of atoms from a Bose-Einstein condensate participating in a superradiance process, which directly reflects the 2nd order coherence of the emitted light. We compare this correlation function with that of atoms undergoing stimulated emission. Whereas the stimulated process produces correlations resembling those of a coherent state, we find that superradiance, even in the presence of strong gain, shows a correlation function close to that of a thermal state, just as for ordinary spontaneous emission.PACS numbers: 03.75. Kk, 67.10.Jn, 42.50.Lc Ever since the publication of Dicke's 1954 paper [1], the problem of the collective emission of radiation has occupied many researchers in the fields of light scattering, lasers and quantum optics. Collective emission is characterized by a rate of emission which is strongly modified compared to that of the individual atoms [2]. It occurs in many different contexts: hot gases, cold gases, solids and even planetary and astrophysical environments [3]. The case of an enhanced rate of emission, originally dubbed superradiance, is closely connected to stimulated emission and gain, and as such resembles laser emission [4]. Lasers are typically characterized by high phase coherence but also by a stable intensity, corresponding to a Poissonian noise, or a flat 2nd order correlation function [5]. Here we present measurements showing that the coherence properties of superradiance, when it occurs in an ultracold gas and despite strong amplified emission, are much closer to those of a thermal state, with super-Poissonian intensity noise.Research has shown that the details of collective emission depend on many parameters such as pumping configuration, dephasing and relaxation processes, sample geometry, the presence of a cavity, etc. and, as a result, a complex nomenclature has evolved including the terms superradiance, superfluorescence, amplified spontaneous emission, mirrorless lasing, and random lasing [2,4,[6][7][8][9], the distinctions among which we will not attempt to summarize here. The problem has recently seen renewed interest in the field of cold atoms [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. This is partly because cold atoms provide a reproducible, easily characterized ensemble in which Doppler broadening effects are small and relaxation is generally limited to spontaneous emission. Most cold atom experiments differ in an important way from the archetypal situation first envisioned by Dicke: instead of creating an ensemble of excited atoms at a well defined time and then allowing this ensemble to evolve freely, the sample is typically pumped during a period long compared to the relaxation time and emission lasts essentially only as long as the pumping. The authors of reference [10] however, have argued that there is a close analogy to the Dicke problem, and we will follow them in designating this process as superradiance.In the literature on superradiance there has been relatively little discussion...

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confidence: 99%

Second-order coherence of superradiance from a Bose-Einstein condensate

et al. 2014

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“…Finally, in a broader context, one expects other situations that generate a scattered atom halo, such as molecular dissociation in a condensate [36,37,[42][43][44][45][46][47][48], atomic parametric down-conversion [4,[49][50][51][52][53], or the interaction of a condensate with barriers and obstacles [54][55][56][57][58], to also be susceptible to the same anisotropy-producing processes. …”

Section: Discussionmentioning

confidence: 99%

“…Of particular interest is the coherent amplification of matter waves [1][2][3][4] and the generation of paircorrelated atoms [5][6][7][8][9]. Atoms scattered during the collision appear in the form of a spherical shell (a "scattering halo"), with strong correlations in diametrically opposed regions.…”

Section: Introductionmentioning

confidence: 99%

Anisotropy ins-wave Bose-Einstein condensate collisions and its relationship to superradiance

et al. 2014

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We report the experimental realization of a single-species atomic four-wave mixing process with BoseEinstein-condensate collisions for which the angular distribution of scattered atom pairs is not isotropic, despite the collisions being in the s-wave regime. Theoretical analysis indicates that this anomalous behavior can be explained by the anisotropic nature of the gain in the medium. There are two competing anisotropic processes: classical trajectory deflections due to the mean-field potential and Bose-enhanced scattering which bears similarity to superradiance. We analyze the relative importance of these processes in the dynamical buildup of the anisotropic density distribution of scattered atoms and compare the Bose enhancement effects to those in optically pumped superradiance.

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“…However, the recent advances in the control of ultracold atoms suggest that it will be possible to carry out similar experiments with material particles. In particular, tailored Einstein-Podolsky-Rosen (EPR) entangled atom pairs can be produced by dissociating Feshbach molecules [13][14][15][16] or by colliding Bose-Einstein condensates [17][18][19][20], in a process similar to parametric down conversion of laser light, the established method to generate entanglement among photons [21].…”

Section: Introductionmentioning

confidence: 99%