BEGIN:VCALENDAR
VERSION:2.0
CALSCALE:GREGORIAN
PRODID:UW-Madison-Physics-Events
BEGIN:VEVENT
SEQUENCE:0
UID:UW-Physics-Event-1516
DTSTART:20090917T150000Z
DURATION:PT1H0M0S
DTSTAMP:20260422T145317Z
LAST-MODIFIED:20090826T124635Z
LOCATION:5310 Chamberlin
SUMMARY:Optimal quantum gates in imperfect qubits\, R. G. Herb Condens
 ed Matter Seminar\, Frank Wilhelm\, University of Waterloo & ICQ
DESCRIPTION:Physical qubits are necessarily not perfect: they typicall
 y contain higher levels beyond the two-state Hilbert space of a qubit 
 and couple to decoherence mechanisms. We show how optimal control theo
 ry helps to accommodate these imperfections and still realize fast hig
 h-fidelity quantum gates. For the case of a weakly anharmonic multilev
 el system containing a qubit\, we introduce the derivative removal by 
 adiabatic gate (DRAG) technique that retains adiabaticity even for fas
 t gates. This technique allows improvement of gate fidelity in realist
 ic superconducting setups by an order of magnitude beyond the present 
 state of the art and to get close to the fault-tolerance threshold [1]
  and beyond\, if multiple carrier frequencies are used. In the case of
  non-Markovian decoherence\, optimal gates are extremely short Rabi bu
 rsts at the optimum working point\, which are modulated to refocus cou
 nter-rotating terms [2].<br>
\n<br>
\n[1] F. Motzoi\, J. M. Gambetta\,
  P. Rebentrost\, and F. K. Wilhelm\, Phys. Rev. Lett.\, in press\, arX
 iv:0901.0534.<br>
\n[2] P. Rebentrost\, I. Serban\, T. Schulte-Herbrue
 ggen\, and F. K. Wilhelm\, Phys. Rev. Lett. 102\, 090401 (2009).
URL:https://www.physics.wisc.edu/events/?id=1516
END:VEVENT
END:VCALENDAR