dorsal/arxiv
View SchemaStrengthened Bell inequalities for orthogonal spin directions
| Authors | J. Uffink, M. Seevinck |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0604145 |
| URL | https://arxiv.org/abs/quant-ph/0604145 |
| DOI | 10.1016/j.physleta.2007.09.033 |
| Journal | Physics Letters A, vol. 372, 1205 (2008) |
Abstract
We strengthen the bound on the correlations of two spin-1/2 particles (qubits) in separable (non-entangled) states for locally orthogonal spin directions by much tighter bounds than the well-known Bell inequality. This provides a sharper criterion for the experimental distinction between entangled and separable states, and even one which is a necessary and sufficient condition for separability. However, these improved bounds do not apply to local hidden-variable theories, and hence they provide a criterion to test the correlations allowed by local hidden-variable theories against those allowed by separable quantum states. Furthermore, these bounds are stronger than some recent alternative experimentally accessible entanglement criteria. We also address the issue of finding a finite subset of these inequalities that would already form a necessary and sufficient condition for non-entanglement. For mixed state we have not been able to resolve this, but for pure states a set of six inequalities using only three sets of orthogonal observables is shown to be already necessary and sufficient for separability.
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"abstract": "We strengthen the bound on the correlations of two spin-1/2 particles\n(qubits) in separable (non-entangled) states for locally orthogonal spin\ndirections by much tighter bounds than the well-known Bell inequality. This\nprovides a sharper criterion for the experimental distinction between entangled\nand separable states, and even one which is a necessary and sufficient\ncondition for separability. However, these improved bounds do not apply to\nlocal hidden-variable theories, and hence they provide a criterion to test the\ncorrelations allowed by local hidden-variable theories against those allowed by\nseparable quantum states. Furthermore, these bounds are stronger than some\nrecent alternative experimentally accessible entanglement criteria. We also\naddress the issue of finding a finite subset of these inequalities that would\nalready form a necessary and sufficient condition for non-entanglement. For\nmixed state we have not been able to resolve this, but for pure states a set of\nsix inequalities using only three sets of orthogonal observables is shown to be\nalready necessary and sufficient for separability.",
"arxiv_id": "quant-ph/0604145",
"authors": [
"J. Uffink",
"M. Seevinck"
],
"categories": [
"quant-ph"
],
"doi": "10.1016/j.physleta.2007.09.033",
"journal_ref": "Physics Letters A, vol. 372, 1205 (2008)",
"title": "Strengthened Bell inequalities for orthogonal spin directions",
"url": "https://arxiv.org/abs/quant-ph/0604145"
},
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