dorsal/arxiv
View SchemaThe hidden phase of Fock states; quantum non-local effects
| Authors | Franck Laloë |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0409097 |
| URL | https://arxiv.org/abs/quant-ph/0409097 |
| DOI | 10.1140/epjd/e2005-00014-0 |
| Journal | European Physical Journal D 33 (2005) 87-97 |
Abstract
We revisit the question of how a definite phase between Bose-Einstein condensates can spontaneously appear under the effect of measurements. We first consider a system that is the juxtaposition of two subsystems in Fock states with high populations, and assume that successive individual position measurements are performed. Initially, the relative phase is totally undefined, and no interference effect takes place in the first position measurement. But, while successive measurements are accumulated, the relative phase becomes better and better known, and a clear interference pattern emerges. It turns out that all observed results can be interpreted in terms of a pre-existing, but totally unknown, relative phase, which remains exactly constant during the experiment. We then generalize the results to more condensates. We also consider other initial quantum states than pure Fock states, and distinguish between intrinsic phase of a quantum state and phase induced by measurements. Finally, we examine the case of multiple condensates of spin states. We discuss a curious quantum effect, where the measurement of the spin angular momentum of a small number of particles can induce a big angular momentum in a much larger assembly of particles, even at an arbitrary distance. This spin observable can be macroscopic, assimilable to the pointer of a measurement apparatus, which illustrates the non-locality of quantum mechanics with particular clarity.
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"abstract": "We revisit the question of how a definite phase between Bose-Einstein\ncondensates can spontaneously appear under the effect of measurements. We first\nconsider a system that is the juxtaposition of two subsystems in Fock states\nwith high populations, and assume that successive individual position\nmeasurements are performed. Initially, the relative phase is totally undefined,\nand no interference effect takes place in the first position measurement. But,\nwhile successive measurements are accumulated, the relative phase becomes\nbetter and better known, and a clear interference pattern emerges. It turns out\nthat all observed results can be interpreted in terms of a pre-existing, but\ntotally unknown, relative phase, which remains exactly constant during the\nexperiment. We then generalize the results to more condensates. We also\nconsider other initial quantum states than pure Fock states, and distinguish\nbetween intrinsic phase of a quantum state and phase induced by measurements.\nFinally, we examine the case of multiple condensates of spin states. We discuss\na curious quantum effect, where the measurement of the spin angular momentum of\na small number of particles can induce a big angular momentum in a much larger\nassembly of particles, even at an arbitrary distance. This spin observable can\nbe macroscopic, assimilable to the pointer of a measurement apparatus, which\nillustrates the non-locality of quantum mechanics with particular clarity.",
"arxiv_id": "quant-ph/0409097",
"authors": [
"Franck Lalo\u00eb"
],
"categories": [
"quant-ph"
],
"doi": "10.1140/epjd/e2005-00014-0",
"journal_ref": "European Physical Journal D 33 (2005) 87-97",
"title": "The hidden phase of Fock states; quantum non-local effects",
"url": "https://arxiv.org/abs/quant-ph/0409097"
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