Controlled dynamics of qubits in the presence of decoherence
Abstract
An exactly solvable model for the decoherence of one and twoqubit states interacting with a spin bath, in the presence of a timedependent magnetic field is studied. The magnetic field is static along ẑ direction and oscillatory in the transverse plane. The transition probability and Rabi oscillations between the spin states of a single qubit is shown to depend on the size of bath, the distribution of qubitbath couplings, and the initial bath polarization. In contrast to the fast Gaussian decay for short times, the polarization of the qubit shows an oscillatory powerlaw decay for long times. The loss of entanglement for the maximally entangled twoqubit states can be controlled by tuning the frequency of the rotating field. The decay rates of entanglement and purity for all the Bell states are the same when the qubits are noninteracting, and different when they are interacting.
 Publication:

Physical Review A
 Pub Date:
 October 2007
 DOI:
 10.1103/PhysRevA.76.042312
 arXiv:
 arXiv:0706.2757
 Bibcode:
 2007PhRvA..76d2312B
 Keywords:

 03.67.Lx;
 03.65.Yz;
 73.21.La;
 85.35.Be;
 Quantum computation;
 Decoherence;
 open systems;
 quantum statistical methods;
 Quantum dots;
 Quantum well devices;
 Quantum Physics;
 Condensed Matter  Mesoscale and Nanoscale Physics
 EPrint:
 9 pages, 7 figures