• myGriffith
    • Staff portal
    • Contact Us⌄
      • Future student enquiries 1800 677 728
      • Current student enquiries 1800 154 055
      • International enquiries +61 7 3735 6425
      • General enquiries 07 3735 7111
      • Online enquiries
      • Staff phonebook
    View Item 
    •   Home
    • Griffith Research Online
    • Journal articles
    • View Item
    • Home
    • Griffith Research Online
    • Journal articles
    • View Item
    JavaScript is disabled for your browser. Some features of this site may not work without it.

    Browse

  • All of Griffith Research Online
    • Communities & Collections
    • Authors
    • By Issue Date
    • Titles
  • This Collection
    • Authors
    • By Issue Date
    • Titles
  • Statistics

  • Most Popular Items
  • Statistics by Country
  • Most Popular Authors
  • Support

  • Contact us
  • FAQs
  • Admin login

  • Login
  • Qubit purification speed-up for three complementary continuous measurements

    Thumbnail
    View/Open
    81508_1.pdf (207.8Kb)
    Author(s)
    Ruskov, Rusko
    Combes, Joshua
    Molmer, Klaus
    Wiseman, Howard M
    Griffith University Author(s)
    Wiseman, Howard M.
    Year published
    2012
    Metadata
    Show full item record
    Abstract
    We consider qubit purification under simultaneous continuous measurement of the three non-commuting qubit operators /sigma_x, /sigma_y, /sigma_z. The purification dynamics is quantified by (i) the average purification rate, and (ii) the mean time of reaching given level of purity, (1-/epsilon). Under ideal measurements (detector efficiency /eta=1), we show in the first case an asymptotic mean purification speed-up of 4 as compared to a standard (classical) single-detector measurement. However by the second measure --- the mean time of first passage T(/epsilon) of the purity --- the corresponding speed-up is only 2. We explain ...
    View more >
    We consider qubit purification under simultaneous continuous measurement of the three non-commuting qubit operators /sigma_x, /sigma_y, /sigma_z. The purification dynamics is quantified by (i) the average purification rate, and (ii) the mean time of reaching given level of purity, (1-/epsilon). Under ideal measurements (detector efficiency /eta=1), we show in the first case an asymptotic mean purification speed-up of 4 as compared to a standard (classical) single-detector measurement. However by the second measure --- the mean time of first passage T(/epsilon) of the purity --- the corresponding speed-up is only 2. We explain these speed-ups using the isotropy of the qubit evolution that provides an equivalence between the original measurement directions and three simultaneous measurements, one with an axis aligned along the Bloch vector and the other with axes in the two complementary directions. For inefficient detectors, /eta=1-/delta <1 the mean time of first passage T(/delta,/epsilon) increases since qubit purification competes with an isotropic qubit dephasing. In the asymptotic high-purity limit (/epsilon, /delta << 1) we show that the increase possesses a scaling behavior: /Delta T(/delta,/epsilon) is a function only of the ratio {/delta}/{/epsilon}. The increase /Delta T({/delta}/{/epsilon}) is linear for small argument but becomes exponential ~ exp({/delta}/2{/epsilon}) for {/delta}/{/epsilon} large.
    View less >
    Journal Title
    Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences
    Volume
    370
    DOI
    https://doi.org/10.1098/rsta.2011.0516
    Copyright Statement
    © 2012 Royal Society. This is the author-manuscript version of this paper. Reproduced in accordance with the copyright policy of the publisher. Please refer to the journal website for access to the definitive, published version.
    Subject
    Quantum information, computation and communication
    Publication URI
    http://hdl.handle.net/10072/48568
    Collection
    • Journal articles

    Footer

    Disclaimer

    • Privacy policy
    • Copyright matters
    • CRICOS Provider - 00233E
    • TEQSA: PRV12076

    Tagline

    • Gold Coast
    • Logan
    • Brisbane - Queensland, Australia
    First Peoples of Australia
    • Aboriginal
    • Torres Strait Islander