1,155 research outputs found
On geometric phases for quantum trajectories
A sequence of completely positive maps can be decomposed into quantum
trajectories. The geometric phase or holonomy of such a trajectory is
delineated. For nonpure initial states, it is shown that well-defined
holonomies can be assigned by using Uhlmann's concept of parallel transport
along the individual trajectories. We put forward an experimental realization
of the geometric phase for a quantum trajectory in interferometry. We argue
that the average over the phase factors for all quantum trajectories that build
up a given open system evolution, fails to reflect the geometry of the open
system evolution itself.Comment: Submitted to the Proceedings of the 13th CEWQO 2006 in Vienn
Validity of rotating wave approximation in non-adiabatic holonomic quantum computation
We examine the validity of the rotating wave approximation (RWA) in
non-adiabatic holonomic single-qubit gates [New J. Phys. {\bf 14}, 103035
(2012)]. We demonstrate that the adoption of RWA may lead to a sharp decline in
fidelity for rapid gate implementation and small energy separation between the
excited and computational states. The validity of the RWA in the recent
experimental realization [Nature (London) {\bf 496}, 482 (2013)] of
non-adiabatic holonomic quantum computation for a superconducting qubit is
examined.Comment: Changes, old figure replaced two new figures, journal reference adde
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