Publication Date:
2012-11-28
Description:
We consider qubit purification under simultaneous continuous measurement of the three non-commuting qubit operators , , . The purification dynamics is quantified by (i) the average purification rate and (ii) the mean time of reaching a given level of purity, 1− ε . Under ideal measurements (detector efficiency η =1), we show in the first case an asymptotic mean purification speed-up of 4 when compared with a standard (classical) single-detector measurement. However, by the second measure—the mean time of first passage 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, η =1− δ
Print ISSN:
1364-503X
Electronic ISSN:
1471-2962
Topics:
Mathematics
,
Physics
,
Technology
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