Experimental test of Bohr's complementarity principle with single neutral atoms

Abstract

An experimental test of quantum complementarity principle based on single neutral atom trapped in a blue detuned bottle trap was here performed. A Ramsey interferometer was used to assess the wavelike behavior or particle-like behavior with second π/2-rotation on or off. The wavelike behavior or particle-like behavior is characterized by the visibility V of the interference or the predictability P of which-path information, respectively. The measured results fulfill the complementarity relation P 2 +V 2 ≤ 1. Imbalance losses were deliberately introduced to the stem and find the complementarity relation is then formally "violated." All the experimental results can be completely explained theoretically by quantum mechanics without considering the interference between wave and particle behaviors. This observation complements existing information concerning the BCP based on waveparticle duality of massive quantum.Bohr's complementarity principle (BCP) is one of the cornerstones of quantum mechanics, and the counterintuitive behavior of wave-particle duality lies at its heart [1]. BCP says that the properties of waves and particles for a quantum system cannot be simultaneously observed. Various tests of BCP with single photons have been performed [2-10]. However, the low detection efficiency associated with fast-moving, massless photons makes the results less persuasive and quite untenable. Here we use a well-controlled, massive, single trapped Cesium atom in a Ramsey interferometer to test BCP of wave-particle duality. A single atom is detected with much greater efficiency and our results confirm the complementarity relation. We also deliberately introduce imbalance losses into our system and find the complementarity relation is formally "violated". The whole experiment is closer to the classical notions, and the result is more ideal than ever, which makes BCP seem even more firm. Our observation provides an important complementation to understand the BCP of wave-particle duality. The system paves a way to observe selectively the wave-particle properties on a single quantum level for massive particles.Wheeler's gedanken delayed-choice experiment [11,12] and the corresponding realizations [6,7,9,13] reveal the nature of the fundamental particles of photons or atoms; they simultaneously possess behaviors of wave-particle duality until the detection arrangement forces them to behave as either one or the superposition of both. In a two-path interferometer, e.g., a Mach-Zehnder interferometer [MZI, see Fig. 1(a)], by moving the second beam splitter (BS) BS2 in or out, we can examine the two exclusive properties of waves and particles, respectively. With the BS2 in the MZI, there is interference between the two paths. By varying the phase difference between these two paths, we can observe an interference fringe, and thus we * gangli@sxu.edu.cn † tczhang@sxu.edu.cn can observe the pure wave property. When the second BS is moved out, the MZI is open and the two detectors detect the particle from two separate paths. Which-pa...

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