Information about the state of a charge qubit gained by a weakly coupled quantum point contact

Sahel Ashhab, J. Q. You, Franco Nori

Research output: Chapter in Book/Report/Conference proceedingConference contribution

17 Citations (Scopus)


We analyze the information that one can learn about the state of a quantum two-level system, i.e. a qubit, when probed weakly by a nearby detector. We consider the general case where the qubit Hamiltonian and the qubit's operator probed by the detector do not commute. Because the qubit's state keeps evolving while being probed and the measurement data is mixed with a detector-related background noise, one might expect the detector to fail in this case. We show, however, that under suitable conditions and by proper analysis of the measurement data, useful information about the initial state of the qubit can be extracted. Our approach complements the usual master-equation and quantum-trajectory approaches, which describe the evolution of the qubit's quantum state during the measurement process but do not keep track of the acquired measurement information.

Original languageEnglish
Title of host publicationPhysica Scripta T
Publication statusPublished - 2009
Externally publishedYes
EventNobel Symposium 141: Qubits for Future Quantum Information - Gothenburg, Sweden
Duration: 25 May 200928 May 2009


OtherNobel Symposium 141: Qubits for Future Quantum Information


ASJC Scopus subject areas

  • Physics and Astronomy(all)

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