The Hanbury Brown-Twiss effect in a pulsed atom laser

Physical Review Letters, 1996

We have determined the rate of loss of atoms from a Bose-Einstein condensed gas due to binary processes in the presence of a far-detuned laser field. In this limit, the binary loss rate spectrum is markedly different from, and can greatly exceed, the basic atomic loss rate. We suggest that measurements of the loss rate spectrum can be used to determine the nature of atom interactions in a condensate. [S0031-9007(96)00919-2]

Physical Review A, 1999

We develop the quantum-mechanical description of output coupling of macroscopic coherent matter waves from a Bose-Einstein condensate ͑BEC͒ via a radio-frequency field in the pulsed and cw limits for both strong and weak field coupling. The theory is converted into a Fock state description to point out the stimulated ͑in Bose particle͒ nature of the output coupling. A useful analogy with the theory of molecular photodissociation is used to explain the various regimes of output coupling BECs using radiation sources. We present specific calculations of the rates of output coupling as a function of the number of Bose atoms in the condensate and the frequency, detuning, and intensity of the radio-frequency field. ͓S1050-2947͑99͒00805-7͔

After reviewing the interpretation of laser operation as a non-equilibrium Bose-Einstein condensation phase transition, we illustrate the novel features arising from the non-equilibrium nature of photon and polariton Bose-Einstein condensates recently observed in experiments. We then proposea quantitative criterion to experimentally assess the equilibrium vs. non-equilibrium nature of a specific condensation process, based on fluctuation-dissipation relations. The power of this criterion is illustrated on two models which shows very different behaviours.

1998

For a dilute, interacting Bose gas of magnetically-trapped atoms at temperatures below the critical temperature T 0 for Bose-Einstein condensation, we determine the second-order coherence function g (2) (r 1 , r 2) within the framework of a finite-temperature quantum field theory. We show that, because of the different spatial distributions of condensate and thermal atoms in the trap, g (2) (r 1 , r 2) does not depend on |r 1 − r 2 | alone. This means that the experimental determinations of g (2) reported to date give only its spatial average. Such an average may underestimate the degree of coherence attainable in an atom laser by judicious engineering of the output coupler.

Physical Review A, 2002

In this work we investigate scattering of ultrashort light pulses from two coupled neutral atomic Bose-Einstein condensates corresponding to two different ground hyperfine sublevels. Two counterpropagating ϩ and Ϫ light waves are employed to excite the atomic condensates. We find that the spectrum of scattered light is determined by the initial preparation of the atomic condensate. The spectrum is found to be a mirror image of the population distribution. The scattered light probes the population distribution between the two condensates. In particular, we find that, when the population is equally distributed between the two ground states, the quantum fluctuations in the spectrum are suppressed due to destructive quantum interference.

Optics Express, 1997

For a dilute, interacting Bose gas of magnetically-trapped atoms at temperatures below the critical temperature T 0 for Bose-Einstein condensation, we determine the second-order coherence function g (2) (r 1 , r 2) within the framework of a finite-temperature quantum field theory. We show that, because of the different spatial distributions of condensate and thermal atoms in the trap, g (2) (r 1 , r 2) does not depend on |r 1 − r 2 | alone. This means that the experimental determinations of g (2) reported to date give only its spatial average. Such an average may underestimate the degree of coherence attainable in an atom laser by judicious engineering of the output coupler.

Physical Review A, 2003

We present a quantum description of the interaction between a Bose-Einstein condensate and a single-mode quantized radiation field in the presence of a strong far-off-resonant pump laser. In the linear regime, the atomic medium is described approximately by two momentum states coupled to the radiation mode. We calculate the evolution of the operators in the Heisenberg picture and their expectation values, such as average and variance of the occupation numbers, atom-atom and atom-field correlations, and two-mode squeezing parameters. Then, we disentangle the evolution operator and obtain the exact evolution of the state vector in the linear regime. This allows us to demostrate that the system can be atom-atom or atom-field thermally entangled. We define the quasiclassical and the quantum recoil limits, for which explicit expressions of the average population numbers are obtained.

Physical Review A, 2002

We discuss the dynamics of a Bose-Einstein condensate during its nondestructive imaging. A generalized Lindblad superoperator in the condensate master equation is used to include the effect of the measurement. A continuous imaging with a sufficiently high laser intensity progressively drives the quantum state of the condensate into number squeezed states. Observable consequences of such a measurementinduced squeezing are discussed. 03.75.Fi, 42.50.Md Since its birth, quantum mechanics has led to an interpretational debate on the role played by the measurement process in its structure and its relationship to classical mechanics developed for macroscopic systems . This debate has been enriched by the realization of new experimental techniques spanning from quantum jumps in single ion traps to macroscopic entangled states in various quantum systems. Recently, the production of atomic Bose-Einstein condensates of dilute atomic gases has also paved the way to the study of dynamical phenomena of macroscopic quantum systems with the precision characteristic of atomic physics .

Technical Digest. 1998 EQEC. European Quantum Electronics Conference (Cat. No.98TH8326), 1998

This paper presents fundamental principles, characteristics and limitations of various experimental methods of cooling and trapping of neutral atoms by laser light and magnetic fields. In addition to surveying the experimental techniques, basic properties of quantum degenerate gases are discussed with particular emphasis on the Bose-Einstein condensate. We also present main parameters and expected characteristics of the first Polish BEC apparatus build in the National Laboratory of Atomic, Molecular and Optical Physics.

Nature Physics, 2012

Hanbury Brown and Twiss correlations-correlations in farfield intensity fluctuations-yield fundamental information on the quantum statistics of light sources, as demonstrated after the discovery of photon bunching 1-3 . Drawing on the analogy between photons and atoms, similar measurements have been performed for matter-wave sources, probing density fluctuations of expanding ultracold Bose gases 4-8 . Here we use two-point density correlations to study how coherence is gradually established when crossing the Bose-Einstein condensation threshold. Our experiments reveal a persistent multimode character of the emerging matter-wave as seen in the non-trivial spatial shape of the correlation functions for all probed source geometries, from nearly isotropic to quasi-onedimensional, and for all probed temperatures. The qualitative features of our observations are captured by ideal Bose gas theory 9 , whereas the quantitative differences illustrate the role of particle interactions.