相干量子摇摆棘轮中输运共振的实验控制
Experimental control of transport resonances in a coherent quantum rocking ratchet
摘要：
棘轮现象是一种在没有净力的情况下获得定向输运的方法。棘轮效应最初被认为是为了纠正随机运动并描述生物马达的工作原理，可以用来实现可控的相干量子输运。这种传输是包括原子芯片在内的几种前景量子器件的组成部分。本文研究了超冷原子在摇摆量子棘轮中的相干输运。这是通过将铷原子玻色-爱因斯坦凝聚体加载到受到双谐时间驱动的周期性光学势中来实现的。实现的长时间的相干性，使我们能够解决共振增强的原子输运引起的避免交叉的Floquet频谱的系统。通过调节时间调制的强度，我们观察到一个单共振到一个双峰的分叉。我们的测量揭示了量子棘轮输运的Floquet本征态之间的相互作用的作用。
英文摘要：
The ratchet phenomenon is a means to get directed transport without net forces. Originally conceived to rectify stochastic motion and describe operational principles of biological motors, the ratchet effect can be used to achieve controllable coherent quantum transport. This transport is an ingredient of several perspective quantum devices including atomic chips. Here we examine coherent transport of ultra-cold atoms in a rocking quantum ratchet. This is realized by loading a rubidium atomic Bose-Einstein condensate into a periodic optical potential subjected to a biharmonic temporal drive. The achieved long-time coherence allows us to resolve resonance enhancement of the atom transport induced by avoided crossings in the Floquet spectrum of the system. By tuning the strength of the temporal modulations, we observe a bifurcation of a single resonance into a doublet. Our measurements reveal the role of interactions among Floquet eigenstates for quantum ratchet transport.
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