Coherent Decay of BoseEinstein Condensates
Abstract
Atomic BoseEinstein condensates are singular forms of matter with the coherence between constituent atoms as a defining characteristic. Although this viewpoint is increasingly validated through experimental findings, the mechanisms behind the observed losses are still understood with classical recombinant collision arguments between particles within the condensate itself. By incorporating a general interparticle interaction into the Hamiltonian, a coherent decay rate can be obtained, thus providing a direct link between the observed losses and the microscopic twobody parameters. Appearing in the lifetime, the interaction strength, {lambda}, is expressed as {lambda}=8{pi}a/(1{delta}), where the small parameter {delta} is obtained from a fit to experimental loss data. Most importantly, the lowest order rate exhibits a novel density dependence ({rho}{sup 3/2}) that can be identified in low temperature tests.
 Authors:
 Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
 Center for Theoretical Physics, Laboratory for Nuclear Science, and Department of Physics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 (United States)
 Publication Date:
 OSTI Identifier:
 20957670
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Physical Review Letters; Journal Volume: 98; Journal Issue: 8; Other Information: DOI: 10.1103/PhysRevLett.98.080405; (c) 2007 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 74 ATOMIC AND MOLECULAR PHYSICS; BOSEEINSTEIN CONDENSATION; COLLISIONS; HAMILTONIANS; LIFETIME; MATTER; TWOBODY PROBLEM
Citation Formats
Cragg, George E., and Kerman, Arthur K.. Coherent Decay of BoseEinstein Condensates. United States: N. p., 2007.
Web. doi:10.1103/PHYSREVLETT.98.080405.
Cragg, George E., & Kerman, Arthur K.. Coherent Decay of BoseEinstein Condensates. United States. doi:10.1103/PHYSREVLETT.98.080405.
Cragg, George E., and Kerman, Arthur K.. Fri .
"Coherent Decay of BoseEinstein Condensates". United States.
doi:10.1103/PHYSREVLETT.98.080405.
@article{osti_20957670,
title = {Coherent Decay of BoseEinstein Condensates},
author = {Cragg, George E. and Kerman, Arthur K.},
abstractNote = {Atomic BoseEinstein condensates are singular forms of matter with the coherence between constituent atoms as a defining characteristic. Although this viewpoint is increasingly validated through experimental findings, the mechanisms behind the observed losses are still understood with classical recombinant collision arguments between particles within the condensate itself. By incorporating a general interparticle interaction into the Hamiltonian, a coherent decay rate can be obtained, thus providing a direct link between the observed losses and the microscopic twobody parameters. Appearing in the lifetime, the interaction strength, {lambda}, is expressed as {lambda}=8{pi}a/(1{delta}), where the small parameter {delta} is obtained from a fit to experimental loss data. Most importantly, the lowest order rate exhibits a novel density dependence ({rho}{sup 3/2}) that can be identified in low temperature tests.},
doi = {10.1103/PHYSREVLETT.98.080405},
journal = {Physical Review Letters},
number = 8,
volume = 98,
place = {United States},
year = {Fri Feb 23 00:00:00 EST 2007},
month = {Fri Feb 23 00:00:00 EST 2007}
}

We study, both experimentally and theoretically, shorttime modifications of the decay of excitations in a BoseEinstein Condensate (BEC) embedded in an optical lattice. Strong enhancement of the decay is observed compared to the Golden Rule results. This enhancement of decay increases with the lattice depth. It indicates that the description of decay modifications of fewbody quantum systems also holds for decay of manybody excitations of a BEC.

Quantum Coherent Atomic Tunneling between Two Trapped BoseEinstein Condensates
We study the coherent atomic tunneling between two zerotemperature BoseEinstein condensates (BEC) confined in a doublewell magnetic trap. Two GrossPitaevskii equations for the selfinteracting BEC amplitudes, coupled by a transfer matrix element, describe the dynamics in terms of the interwell phase difference and population imbalance. In addition to the anharmonic generalization of the familiar ac Josephson effect and plasma oscillations occurring in superconductor junctions, the nonlinear BEC tunneling dynamics sustains a selfmaintained population imbalance: a novel {open_quotes}macroscopic quantum selftrapping{close_quotes} effect. {copyright} {ital 1997} {ital The American Physical Society} 
Quantum coherence of doublewell BoseEinstein condensates: An SU(2) coherentstate pathintegral approach
Macroscopic quantum coherence of Bose gas in a doublewell potential is studied, based on an SU(2) coherentstate pathintegral approach. The ground state and fluctuations around it can be obtained by this method. In this picture, one can obtain macroscopic quantum superposition states for attractive Bose gas. The coherent gap of degenerate ground states is obtained with the instanton technique. The phenomenon of macroscopic quantum selftrapping is also discussed. 
Generalized coherent state representation of BoseEinstein condensates
We show that the quantum manybody state of BoseEinstein condensates consistent with the timedependent HartreeFockBogoliubov (TDHFB) equations is a generalized coherent state. At zero temperature, the noncondensate density and the anomalous noncondensate correlation are not independent, allowing us to eliminate one of the three variables in the TDHFB. 
Energyband structure and intrinsic coherent properties in two weakly linked BoseEinstein condensates
The energyband structure and energy splitting due to quantum tunneling in two weakly linked BoseEinstein condensates were calculated by using the instanton method. The intrinsic coherent properties of BoseJosephson junction (BJJ) were investigated in terms of energy splitting. For E{sub C}/E{sub J}<<1, the energy splitting is small and the system is globally phase coherent. In the opposite limit, E{sub C}/E{sub J}>>1, the energy splitting is large and the system becomes phase dissipated. Our results suggest that one should investigate the coherence phenomena of BJJ in proper condition such as E{sub C}/E{sub J}{approx}1.