| 日時: |
2008-12-10 16:00 - 17:00 |
| 場所: |
研究本館３階３２１室 |
| 会議名: |
Can a single particle be at two places at the same time? |
| 連絡先: |
市川翼 |
| 講演者: |
Dr. Gunnar BJORK (Royal Institute of Technology, Stockholm) |
| アブストラクト: |
Einstein, Podolsky and Rosen's (EPR) seminal paper on quantum correlations of entangled states, and Bell's subsequent discovery that quantum theory is incompatible with any locally realistic hidden variable theory, have spurred substantial discussion and many experiments on the nature of quantum nonlocality and entanglement. Most experimental tests follow Bohm and Aharonov's reformulation of EPR's gedanken experiment. Hence, the experiments involve two space-like separated entangled particles, typically two polarization entangled photons.
In 1990, Tan, Walls, and Collet proposed a test of nonlocality involving only one particle, a single photon. Their proposal initiated a debate if it is indeed possible for a single particle to have measurable (and correlated) properties at two space-like separated locations? The two main argument against this possibility were: 1) that detection of the particle at one location would immediately nullify any possibility of recording any property associated with the particle (except for its absence) at any other location, and 2) that detection of the particle would typically involve the simultaneous detection of particles from auxiliary states (e.g., a local oscillator), compromising the notion of single particle nonlocality.
We have performed an experiment where the properties of a single photon, split between two spatial modes, are measured. We measure the relative phase between the superposition between zero and one photon at two locations, by co-propagating a local oscillator in the same spatial mode, but with an orthogonal polarization. The obtained correlation violates classical physics and clearly support the quantum mechanical predictions. |
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