Dissipative dynamics in a quantum register
Abstract
A model for a quantum register dissipatively coupled with a bosonic thermal bath is studied. The register consists of N quantum bits (qubits) the bath is described by N_{b} bosonic modes. The registerbath coupling is chosen in such a way that the total number of excitations is conserved. The Hilbert space splits, allowing the study of the dynamics separately in each sector. Assuming that the coupling with the bath is the same for all qubits, the excitation sectors have a further decomposition according the irreducible representations of the su(2) spin algebra. The stability against environmentgenerated noise of the information encoded in a quantum state of the register depends on its SU(2) symmetry content. At zero temperature we find that states belonging to the vacuum symmetry sector have, for long time, vanishing fidelity, whereas each lowest spin vector is decoupled from the bath and therefore is decoherence free. Numerical results are shown in the oneexcitation space in the case of qubitdependent bathsystem coupling.
 Publication:

Physical Review A
 Pub Date:
 December 1997
 DOI:
 10.1103/PhysRevA.56.4445
 arXiv:
 arXiv:quantph/9708042
 Bibcode:
 1997PhRvA..56.4445Z
 Keywords:

 03.65.w;
 05.30.Fk;
 Quantum mechanics;
 Fermion systems and electron gas;
 Quantum Physics
 EPrint:
 to appear on Phys. Rev. A, 8 pages + 5 postscript figures