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SUMMARY:How to keep a qubit alive - Prof. John Cardy FRS\, All Souls\, Oxf
 ord
DTSTART:20081113T141500Z
DTEND:20081113T154500Z
UID:TALK13197@talks.cam.ac.uk
CONTACT:Joe Bhaseen
DESCRIPTION:I consider a quantum spin-1/2\, arbitrarily coupled to its env
 ironment\, evolving deterministically under a time-dependent magnetic fiel
 d B(t). I show that one can choose the time-dependence so that decoherence
  effects are minimized\, in the sense that over a finite time interval T\,
  transition rates between different states of the qubit can be suppressed 
 to any desired order in T. Moreover the optimal protocol is independent of
  the details of the interaction hamiltonian and the state of the environme
 nt. This is joint work with D Dhar\, based on work by Uhrig [Phys. Rev. Le
 tt\, 98\, 100504 (2007)] and by Yang and Liu arXiv:0807.4058.
LOCATION:TCM Seminar Room\, Cavendish Laboratory
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