Quantum Control of a Single Qubit

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dc.creatorBranczyk, Agata M.
dc.creatorMendonca, Paulo E. M. F.
dc.creatorGilchrist, Alexei
dc.creatorDoherty, Andrew C.
dc.creatorBartlett, Stephen D.
dc.date2006-08-04
dc.date2006-08-15
dc.date.accessioned2026-07-07T07:43:42Z
dc.date.available2026-07-07T07:43:42Z
dc.descriptionMeasurements 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.
dc.description12 pages, 7 figures, v2 includes new references and minor changes
dc.identifierhttps://arxiv.org/abs/quant-ph/0608037
dc.identifierhttp://arxiv.org/abs/quant-ph/0608037
dc.identifierPhys. Rev. A, 75, 012329 (2007)
dc.identifierdoi:10.1103/PhysRevA.75.012329
dc.identifier.urihttp://salesiana.dossiersoluciones.com/handle/123456789/122933
dc.subjectQuantum Physics
dc.titleQuantum Control of a Single Qubit
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