Rapid purification of a solid state charge qubit
Jason F Ralph, Elias J Griffith, Charles D Hill, Terence D Clark, EJ Donkor (ed.), AR Pirich (ed.), HE Brandt (ed.)
QUANTUM INFORMATION AND COMPUTATION IV | SPIE-INT SOC OPTICAL ENGINEERING | Published : 2006
This paper discusses the use of continuous weak measurement and quantum feedback for the rapid purification of the quantum state of a model solid state qubit: a superconducting Cooper pair box. The feedback algorithm uses Jacobs' rapid purification protocol, which starts with a completely mixed state and applies controls to rotate the qubit Bloch vector onto the plane orthogonal to the measurement axis. This rotation maximises the rate of increase of the average purity of the state but can require large changes in the control fields to produce the required rotation. Since solid state qubits have finite controls and feedback channels have limited bandwidth, such rotations may not be practical..View full abstract
Awarded by UK Engineering and Physical Science Research Council
The authors would like to acknowledge the UK Engineering and Physical Science Research Council (Grant No.: EP/C012674/1(P)) for their generous support of this work. The authors would also like to thank Prof. H. M. Wiseman and Dr. K. Jacobs for useful and informative discussions.