Quantum fluctuations and condensate fraction during the time-of-flight expansion

Understand

The quantum fluctuation effects in the time-of-flight (TOF) experiment for a condensate released from an optical lattice potential is studied within the truncated Wigner approximation.

• By investigating both the spatial and momentum density distributions, we find that the condensate fraction decreases monotonically in time and hence cannot be measured in the standard TOF image.
• We then propose a semi-quantitative analysis for such dynamical quantum depletion process.
• Our study shows a universal algebraic decay of the true condensate fraction, and have a very good agreement with numerical results.