Direct Measurement of Long-Range Third-Order Coherence in Bose-Einstein Condensates

Hodgman, Sean; Dall, Robert; Manning, Andrew; Baldwin, K. G. H.; Truscott, A. G.

doi:10.1126/science.1198481

Cited by 100 publications

(109 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Similar results were obtained in experiments with nondegenerate gas at optical lattices [7] and atomic lasers [8]. Direct measurement of the second and the third order correlation function of Bose-Einstein condensates is an important proof of their high coherence [9].The correlation functions of the atomic field, contrary to the electromagnetic waves, depend not only on the temperature, but also on the interactions and the dimensionality of the system. The density and phase of a threedimensional condensate do not fluctuate.…”

supporting

confidence: 76%

Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

Gawryluk¹,

Gajda²,

Brewczyk

2015

Phys. Rev. A

View full text Add to dashboard Cite

We study, within a framework of the classical fields approximation, the density correlations of a weakly interacting expanding Bose gas for the whole range of temperatures across the Bose-Einstein condensation threshold. We focus on elongated quasi-one-dimensional systems where there is a huge discrepancy between the existing theory and experimental results (A. Perrin et al., Nature Phys. 8, 195 (2012)). We find that the density correlation function is not reduced for temperatures below the critical one as it is predicted for the ideal gas or for a weakly interacting system within the Bogoliubov approximation. This behavior of the density correlations agrees with the above mentioned experiment with the elongated system. Although the system was much larger then studied here we believe that the behavior of the density correlation function found there is quite generic. Our theoretical studies indicate also large density fluctuations in the trap in the quasicondensate regime where only phase fluctuations were expected. We argue that the enhanced density fluctuations can originate in the presence of interactions in the system, or more precisely in the existence of spontaneous dark solitons in the elongated gas at thermal equilibrium.Correlations are the essence of any many body systems. In particular, the quantum features of the system are manifested by some unusual correlations. The first order coherence is the basic criterion used as the definition of a Bose-Einstein condensate. And indeed, very soon after observation of trapped atomic condensates the first order coherence of such systems, manifesting itself in the ability to produce the interference fringes in a two-slit experiment, had been proven [1] experimentally. Higher order correlations leading to atom bunching were established from collisions and three-body losses [2]. Although the Glauber coherence theory introduced to characterize correlations of quantum electromagnetic field is well established now, the issue of coherence of a matter field is still under intensive investigation.A Bose-Einstein condensate is a matter wave analogue of a coherent light. A very important question is how far this analogy can be pursuit. The first difference is that atoms exist in a Fock states only: the states which are the eigenstates of the particle number operator. As a consequence, the coherent state of a matter field, understood as the exact analogue of the coherent electromagnetic field, does not exist. On the other hand, the atomic field can exhibit a higher order coherence too. The coherence ought to be understood here as the ability to produce the interference patterns not only in a single-particle detection schemes, but also in a simultaneous detection of larger number of atoms. Although the phase of a number state can be arbitrary, the Fock states can interfere in a single realization of the system [3] when no averaging over global phase is performed. Therefore higher order coherence of atomic condensates, as can be observed in a single realization of the system,...

show abstract

supporting

confidence: 76%

Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

Gawryluk¹,

Gajda²,

Brewczyk

2015

Phys. Rev. A

View full text Add to dashboard Cite

show abstract

“…2c-e similarly to g (3) , that is, for equal spatial separations for all particles. For atomic systems this is the first reported measurement of the fifth-and sixth-order correlation functions and, importantly, the measurements of the lower-order correlations are up to two orders of magnitude greater in amplitude than previously reported 13,14,21 . Remarkably, the measurement of the six-body correlation function demonstrates that the probability of finding six particles at the same location is nearly three orders of magnitude greater than for large separations.…”

mentioning

confidence: 51%

Ideal n-body correlations with massive particles

et al. 2013

Self Cite

View full text Add to dashboard Cite

In 1963 Glauber introduced the modern theory of quantum coherence 1 , which extended the concept of first-order (onebody) correlations, describing phase coherence of classical waves, to include higher-order (n-body) quantum correlations characterizing the interference of multiple particles. Whereas the quantum coherence of photons is a mature cornerstone of quantum optics, the quantum coherence properties of massive particles remain largely unexplored. To investigate these properties, here we use a uniquely correlated 2 source of atoms that allows us to observe n-body correlations up to the sixthorder at the ideal theoretical limit (n!). Our measurements constitute a direct demonstration of the validity of one of the most widely used theorems in quantum many-body theory-Wick's theorem 3 -for a thermal ensemble of massive particles. Measurements involving n-body correlations may play an important role in the understanding of thermalization of isolated quantum systems 4 and the thermodynamics of exotic many-body systems, such as Efimov trimers 5 .Glauber's modern theory of optical coherence and the famous Hanbury Brown-Twiss effect 6 were pivotal in the establishment of the field of quantum optics. Importantly, the definition of a coherent state required coherence to all orders, which for example distinguishes a monochromatic but incoherent thermal source of light from a truly coherent source such as a laser. Higher-order correlation functions therefore provide a more rigorous test of coherence.Higher-order correlations, characterized by an n-body correlation function g (n) , are of general interest and have been investigated in many fields of physics including astronomy 6 , particle physics 7 , quantum optics 8 , and quantum atom optics 9 . In particular they have been a fruitful area of research in the field of quantum optics, where they have been used to investigate the properties of laser light, including heralded single photons 10 , and the statistics of parametric down-conversion sources 11 . State-of-the-art quantum optics experiments have measured photon correlation functions up to sixth order for quasi-thermal sources 8 , allowing the possibility of performing full quantum state tomography 12 .Higher-order correlations experiments with massive particles are currently approaching the same level of maturity as with photons. So far, experiments have directly observed correlations up to fourth order with single-atom-sensitive detection techniques for ultracold atomic bosons 9,13,14 , and second-order correlations for an atomic source of fermions 15 demonstrating the uniquely quantum mechanical property of atom-atom antibunching. Alternative, indirect techniques have also been employed to investigate higher-order correlations, including the measurements of twobody (photoassociation 16 ) and three-body 17 loss rates that are sensitive, respectively, to second-and third-order correlation functions. Interestingly, fermionic atom pairs 18 and fermionic antibunching 19 have also been observed in the atomic shot no...

show abstract

“…With the rapid progress in quantum gas experiments [16], measuring higher-order correlation functions [17][18][19][20] is now within reach. To illustrate the power of the above concepts to analyse a non trivial interacting quantum many-body system, we experimentally investigate two tunnel-coupled one-dimensional (1D) bosonic superfluids, realised with quantum degenerate 87 Rb atoms trapped in a double-well (DW) potential with a freely relative DOF DW potential adjustable tunnel-coupling FIG.…”

mentioning

confidence: 99%

Experimental characterization of a quantum many-body system via higher-order correlations

Schweigler

Kasper

Erne

et al. 2017

Nature

235

319

View full text Add to dashboard Cite

Direct Measurement of Long-Range Third-Order Coherence in Bose-Einstein Condensates

Cited by 100 publications

References 33 publications

Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

Density fluctuations in a quasi-one-dimensional Bose gas as observed in free expansion

Ideal n-body correlations with massive particles

Experimental characterization of a quantum many-body system via higher-order correlations

Contact Info

Product

Resources

About