Li Yifan, Pawłowski Krzysztof, Décamps Boris, Colciaghi Paolo, Fadel Matteo, Treutlein Philipp, Zibold Tilman
Department of Physics, University of Basel, 4056 Basel, Switzerland.
Department of Engineering Physics, Tsinghua University, Beijing 100084, China.
Phys Rev Lett. 2020 Sep 18;125(12):123402. doi: 10.1103/PhysRevLett.125.123402.
We experimentally and theoretically study phase coherence in two-component Bose-Einstein condensates of ^{87}Rb atoms on an atom chip. Using Ramsey interferometry we determine the temporal decay of coherence between the |F=1,m_{F}=-1⟩ and |F=2,m_{F}=+1⟩ hyperfine ground states. We observe that the coherence is limited by random collisional phase shifts due to the stochastic nature of atom loss. The mechanism is confirmed quantitatively by a quantum trajectory method based on a master equation which takes into account collisional interactions, atom number fluctuations, and losses in the system. This decoherence process can be slowed down by reducing the density of the condensate. Our findings are relevant for experiments on quantum metrology and many-particle entanglement with Bose-Einstein condensates and the development of chip-based atomic clocks.
我们通过实验和理论研究了原子芯片上(^{87}Rb)原子的双组分玻色-爱因斯坦凝聚体中的相位相干性。利用拉姆齐干涉测量法，我们确定了(|F = 1,m_{F} = -1⟩)和(|F = 2,m_{F} = +1⟩)超精细基态之间相干性的时间衰减。我们观察到，由于原子损失的随机性，相干性受到随机碰撞相移的限制。通过基于主方程的量子轨迹方法对该机制进行了定量确认，该主方程考虑了碰撞相互作用、原子数涨落以及系统中的损失。通过降低凝聚体的密度，可以减缓这种退相干过程。我们的研究结果与玻色-爱因斯坦凝聚体的量子计量和多粒子纠缠实验以及基于芯片的原子钟的发展相关。
