dorsal/arxiv
View SchemaQuantum Control of a Single Qubit
| Authors | Agata M. Branczyk, Paulo E. M. F. Mendonca, Alexei Gilchrist, Andrew C. Doherty, Stephen D. Bartlett |
|---|---|
| Categories | |
| ArXiv ID | quant-ph/0608037 |
| URL | https://arxiv.org/abs/quant-ph/0608037 |
| DOI | 10.1103/PhysRevA.75.012329 |
| Journal | Phys. Rev. A, 75, 012329 (2007) |
Abstract
Measurements in quantum mechanics cannot perfectly distinguish all states and necessarily disturb the measured system. We present and analyse a proposal to demonstrate fundamental limits on quantum control of a single qubit arising from these properties of quantum measurements. We consider a qubit prepared in one of two non-orthogonal states and subsequently subjected to dephasing noise. The task is to use measurement and feedback control to attempt to correct the state of the qubit. We demonstrate that projective measurements are not optimal for this task, and that there exists a non-projective measurement with an optimum measurement strength which achieves the best trade-off between gaining information about the system and disturbing it through measurement back-action. We study the performance of a quantum control scheme that makes use of this weak measurement followed by feedback control, and demonstrate that it realises the optimal recovery from noise for this system. We contrast this approach with various classically inspired control schemes.
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"abstract": "Measurements in quantum mechanics cannot perfectly distinguish all states and\nnecessarily disturb the measured system. We present and analyse a proposal to\ndemonstrate fundamental limits on quantum control of a single qubit arising\nfrom these properties of quantum measurements. We consider a qubit prepared in\none of two non-orthogonal states and subsequently subjected to dephasing noise.\nThe task is to use measurement and feedback control to attempt to correct the\nstate of the qubit. We demonstrate that projective measurements are not optimal\nfor this task, and that there exists a non-projective measurement with an\noptimum measurement strength which achieves the best trade-off between gaining\ninformation about the system and disturbing it through measurement back-action.\nWe study the performance of a quantum control scheme that makes use of this\nweak measurement followed by feedback control, and demonstrate that it realises\nthe optimal recovery from noise for this system. We contrast this approach with\nvarious classically inspired control schemes.",
"arxiv_id": "quant-ph/0608037",
"authors": [
"Agata M. Branczyk",
"Paulo E. M. F. Mendonca",
"Alexei Gilchrist",
"Andrew C. Doherty",
"Stephen D. Bartlett"
],
"categories": [
"quant-ph"
],
"doi": "10.1103/PhysRevA.75.012329",
"journal_ref": "Phys. Rev. A, 75, 012329 (2007)",
"title": "Quantum Control of a Single Qubit",
"url": "https://arxiv.org/abs/quant-ph/0608037"
},
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