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arXiv quant-ph/0606128quant-phcond-mat.other
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如何观察原子和分子的相干叠加

How to observe a coherent superposition of an atom and a molecule

Mark R. Dowling, Stephen D. Bartlett, Terry Rudolph, Robert W. Spekkens

摘要:

我们证明,它是可能的,在原则上,进行拉姆齐型干涉实验,表现出一个单原子和双原子分子的相干叠加。这个基于Aharonov和Susskind [Phys. Rev. 155,1428(1967)]技术的gedanken实验明显违反了普遍接受的超选择规则,该规则禁止不同原子数的本征态的相干叠加。该干涉实验利用玻色-爱因斯坦凝聚体作为参考系,进行类似于拉姆齐脉冲的相干操作。我们还研究了一个类似的gedanken实验,表现出一个单一的玻色子和费米子的相干叠加,违反了普遍接受的超选择规则,禁止不同粒子统计状态的相干叠加;在这种情况下,参考系是由许多费米子的多模状态实现的。后一种情况再现了拉姆齐干涉测量的所有相关特征,包括多次重复实验的拉姆齐条纹。然而,这个拟议的实验显然无法在两个不同的系统之间产生定义明确的相对相位,每个系统都由玻色子和费米子的相干叠加描述,这表明要完全“提升”单价超选择规则还有额外的、突出的要求。

英文摘要:

We demonstrate that it is possible, in principle, to perform a Ramsey-type interference experiment to exhibit a coherent superposition of a single atom and a diatomic molecule. This gedanken experiment, based on the techniques of Aharonov and Susskind [Phys. Rev. 155, 1428 (1967)], explicitly violates the commonly-accepted superselection rule that forbids coherent superpositions of eigenstates of differing atom number. This interference experiment makes use of a Bose-Einstein condensate as a reference frame with which to perform the coherent operations analogous to Ramsey pulses. We also investigate an analogous gedanken experiment to exhibit a coherent superposition of a single boson and a fermion, violating the commonly-accepted superselection rule forbidding coherent superpositions of states of differing particle statistics; in this case, the reference frame is realized by a multi-mode state of many fermions. This latter case reproduces all of the relevant features of Ramsey interferometry, including Ramsey fringes over many repetitions of the experiment. However, the apparent inability of this proposed experiment to produce well-defined relative phases between two distinct systems each described by a coherent superposition of a boson and a fermion demonstrates that there are additional, outstanding requirements to fully ``lift'' the univalence superselection rule.

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