Atomic homodyne detection of continuous-variable entangled twin-atom states
Atomic homodyne detection of continuous-variable entangled twin-atom states
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DOI：
10.1038/nature10654
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发表时间：
2011-12-08
期刊：
影响因子：
64.8
通讯作者：
Oberthaler, M. K.
中科院分区：
文献类型：
--
作者：
Gross, C.;Strobel, H.;Oberthaler, M. K.
从历史上看，量子理论的完整性一直被质疑使用的概念，二分连续变量纠缠（1）。两个子系统之间的非经典关联（纠缠）意味着一个子系统的可观测量由另一个子系统的测量选择决定，而不管子系统之间的距离。如今，连续变量纠缠被认为是一种必不可少的资源，允许量子增强测量分辨率（2），实现量子隐形传态（3-5）和量子存储器（3，6），或证明爱因斯坦-波多尔斯基-罗森悖论（1，7 -9）。这些应用依赖于操纵和检测量子场的相干性的技术，即求积。而在光学相干零差检测（10）的正交是一个标准的技术，为大质量粒子的相应方法是失踪。在这里，我们报告的实现原子模拟零差检测测量的物质波求积。将这种技术应用于玻色-爱因斯坦凝聚体（11，12）中自旋变化碰撞产生的量子态，揭示了连续变量纠缠以及态的双原子特征（13）。我们的结果提供了一个罕见的大质量粒子连续变量纠缠的例子（6，14）。原子正交的直接检测不仅在实验量子原子光学中有应用，而且还用于测量大质量粒子的多体系统中的场（15）。
Historically, the completeness of quantum theory has been questioned using the concept of bipartite continuous-variable entanglement(1). The non-classical correlations (entanglement) between the two subsystems imply that the observables of one subsystem are determined by the measurement choice on the other, regardless of the distance between the subsystems. Nowadays, continuous-variable entanglement is regarded as an essential resource, allowing for quantum enhanced measurement resolution(2), the realization of quantum teleportation(3-5) and quantum memories(3,6), or the demonstration of the Einstein-Podolsky-Rosen paradox(1,7-9). These applications rely on techniques to manipulate and detect coherences of quantum fields, the quadratures. Whereas in optics coherent homodyne detection(10) of quadratures is a standard technique, for massive particles a corresponding method was missing. Here we report the realization of an atomic analogue to homodyne detection for the measurement of matter-wave quadratures. The application of this technique to a quantum state produced by spin-changing collisions in a Bose-Einstein condensate(11,12) reveals continuous-variable entanglement, as well as the twin-atom character of the state(13). Our results provide a rare example of continuous-variable entanglement of massive particles(6,14). The direct detection of atomic quadratures has applications not only in experimental quantum atom optics, but also for the measurement of fields in many-body systems of massive particles(15).