Interference between two indistinguishable electrons from independent sources
Interference between two indistinguishable electrons from independent sources
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DOI：
10.1038/nature05955
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发表时间：
2007-07-19
期刊：
影响因子：
64.8
通讯作者：
Umansky, V.
中科院分区：
文献类型：
--
作者：
Neder, I.;Ofek, N.;Umansky, V.
非常类似于单个粒子与其自身普遍存在的量子干涉（1），两个独立但不可区分的粒子的量子干涉也是可能的。对于单个粒子，干涉发生在粒子波函数的振幅之间，而两个粒子之间的干涉是量子交换统计的直接结果。这种干涉只有在两个粒子从两个空间上分离且独立的源注入后，在两个分离的探测器中找到它们的联合概率中才能被观察到。已经有人提出了双粒子干涉仪的实验实现方案（2,3）；在这些方案中表明，这种相关性是两个粒子空间自由度之间量子纠缠（4）（“轨道纠缠”）的直接标志，即使它们彼此之间没有相互作用。在光学中，使用不可区分的光子对的实验在产生独立光子对以及同步它们的到达时间方面遇到了困难；因此它们专注于通过符合测量来检测光子（玻色子）的聚束（5,6）。类似的电子实验相当稀少。来自一个源（7 - 10）的分流电流之间的互相关测量，产生了与自相关（散粒噪声）测量（11,12）所获得的类似信息。参考文献3中的方案是对经典光的历史上的汉伯里·布朗和特维斯实验的电子模拟（13,14）。它基于在量子霍尔效应区域（16）中使用边缘通道的电子马赫 - 曾德尔干涉仪（15）。在这里我们实现了这样一种干涉仪。我们将两束独立且相互不相干的电子束分成两条轨迹，使得合并后的四条轨迹包围一个阿哈罗诺夫 - 玻姆通量。尽管发现单个电流及其涨落（通过自相关测量的散粒噪声）与阿哈罗诺夫 - 玻姆通量无关，但在器件两侧两个相对点处的电流涨落之间的互相关呈现出强烈的阿哈罗诺夫 - 玻姆振荡，这表明两束电子束之间存在轨道纠缠。
Very much like the ubiquitous quantum interference of a single particle with itself(1), quantum interference of two independent, but indistinguishable, particles is also possible. For a single particle, the interference is between the amplitudes of the particle's wave-functions, whereas the interference between two particles is a direct result of quantum exchange statistics. Such interference is observed only in the joint probability of finding the particles in two separated detectors, after they were injected from two spatially separated and independent sources. Experimental realizations of two-particle interferometers have been proposed(2,3); in these proposals it was shown that such correlations are a direct signature of quantum entanglement(4) between the spatial degrees of freedom of the two particles ('orbital entanglement'), even though they do not interact with each other. In optics, experiments using indistinguishable pairs of photons encountered difficulties in generating pairs of independent photons and synchronizing their arrival times; thus they have concentrated on detecting bunching of photons (bosons) by coincidence measurements(5,6). Similar experiments with electrons are rather scarce. Cross-correlation measurements between partitioned currents, emanating from one source(7-10), yielded similar information to that obtained from auto-correlation (shot noise) measurements(11,12). The proposal of ref. 3 is an electronic analogue to the historical Hanbury Brown and Twiss experiment with classical light(13,14). It is based on the electronic Mach-Zehnder interferometer(15) that uses edge channels in the quantum Hall effect regime(16). Here we implement such an interferometer. We partitioned two independent and mutually incoherent electron beams into two trajectories, so that the combined four trajectories enclosed an Aharonov-Bohm flux. Although individual currents and their fluctuations (shot noise measured by auto-correlation) were found to be independent of the Aharonov-Bohm flux, the cross-correlation between current fluctuations at two opposite points across the device exhibited strong Aharonov-Bohm oscillations, suggesting orbital entanglement between the two electron beams.