dorsal/arxiv
View SchemaQuantum coherence in the presence of unobservable quantities
| Authors | Kae Nemoto, Samuel L. Braunstein |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0306084 |
| URL | https://arxiv.org/abs/quant-ph/0306084 |
| DOI | 10.1103/PhysRevA.68.042326 |
Abstract
State representations summarize our knowledge about a system. When unobservable quantities are introduced the state representation is typically no longer unique. However, this non-uniqueness does not affect subsequent inferences based on any observable data. We demonstrate that the inference-free subspace may be extracted whenever the quantity's unobservability is guaranteed by a global conservation law. This result can generalize even without such a guarantee. In particular, we examine the coherent-state representation of a laser where the absolute phase of the electromagnetic field is believed to be unobservable. We show that experimental coherent states may be separated from the inference-free subspaces induced by this unobservable phase. These physical states may then be approximated by coherent states in a relative-phase Hilbert space.
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"abstract": "State representations summarize our knowledge about a system. When\nunobservable quantities are introduced the state representation is typically no\nlonger unique. However, this non-uniqueness does not affect subsequent\ninferences based on any observable data. We demonstrate that the inference-free\nsubspace may be extracted whenever the quantity\u0027s unobservability is guaranteed\nby a global conservation law. This result can generalize even without such a\nguarantee. In particular, we examine the coherent-state representation of a\nlaser where the absolute phase of the electromagnetic field is believed to be\nunobservable. We show that experimental coherent states may be separated from\nthe inference-free subspaces induced by this unobservable phase. These physical\nstates may then be approximated by coherent states in a relative-phase Hilbert\nspace.",
"arxiv_id": "quant-ph/0306084",
"authors": [
"Kae Nemoto",
"Samuel L. Braunstein"
],
"categories": [
"quant-ph"
],
"doi": "10.1103/PhysRevA.68.042326",
"title": "Quantum coherence in the presence of unobservable quantities",
"url": "https://arxiv.org/abs/quant-ph/0306084"
},
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