从磁阱释放后凝聚态量子耗尽的生存
On the survival of the quantum depletion of a condensate after release from a magnetic trap
摘要：
本文观测了亚稳态氦原子从谐波阱中释放出来的膨胀玻色-爱因斯坦凝聚体中的高动量尾。远场密度分布的特点，支持识别的尾巴的动量分布起源于在原位量子耗尽之前释放。因此，我们证实了最近的观察缓慢衰减的尾巴在远场以外的热分量。这一观察结果与流体动力学理论相冲突，流体动力学理论预测，当原子从陷阱中释放出来时，原位耗尽不会存在。事实上，耗尽的尾巴，甚至出现在远场比预期释放前更强，我们讨论了解释这方面的挑战，在被困气体的谭接触。作为对这些观测结果的补充，对实验的完全量子模拟表明，在适当的条件下，耗尽可以在膨胀后持续到远场。此外，模拟提供了生存的机制，并为大动量的尾巴出现更强的膨胀后，由于平均场势的加速耗尽的原子。然而，虽然定性一致，但实验中观察到的最终耗尽比模拟中大得多。
英文摘要：
We present observations of the high momentum tail in expanding Bose-Einstein condensates of metastable Helium atoms released from a harmonic trap. The far-field density profile exhibits features that support identification of the tails of the momentum distribution as originating in the in-situ quantum depletion prior to release. Thus, we corroborate recent observations of slowly-decaying tails in the far-field beyond the thermal component. This observation is in conflict with the hydrodynamic theory, which predicts that the in-situ depletion does not survive when atoms are released from a trap. Indeed, the depleted tails even appear stronger in the far-field than expected before release, and we discuss the challenges of interpreting this in terms of the Tan contact in the trapped gas. In complement to these observations, full quantum simulations of the experiment show that, under the right conditions, the depletion can persist into the far field after expansion. Moreover, the simulations provide mechanisms for survival and for the the large-momentum tails to appear stronger after expansion due to an acceleration of the depleted atoms by the mean-field potential. However, while in qualitative agreement, the final depletion observed in the experiment is much larger than in the simulation.
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