We experimentally and theoretically study phase coherence in two-component Bose-Einstein condensates of ${}^{87}\mathrm{Rb}$ 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.

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两组分玻色-爱因斯坦凝聚物中相干性的基本极限

我们从实验和理论上研究了两组分Bose-Einstein凝聚物中的相干 ${}^{87}b$原子芯片上的原子。使用Ramsey干涉测量法，我们可以确定$|F=\mathrm{1个}，{米}_F=-\mathrm{1个}⟩$ 和 $|F=2，{米}_F=+\mathrm{1个}⟩$超细基态。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。该机制是通过基于主方程的量子轨迹方法定量确定的，该主方程考虑了碰撞相互作用，原子数波动和系统中的损失。可以通过降低冷凝物的密度来减慢此相干过程。我们的发现与量子计量学和玻色-爱因斯坦凝聚物的多粒子纠缠实验以及基于芯片的原子钟的开发有关。