Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
Q: Quantenoptik und Photonik
Q 77: Poster Quantencomputer
Q 77.7: Poster
Donnerstag, 16. März 2006, 16:30–18:30, Labsaal
Stabilizing decoupling and recoupling schemes by randomization — •Oliver Kern and Gernot Alber — Institut für Angewandte Physik, Hochschulstrasse 4a, 64289 Darmstadt, Germany
In quantum information processing the presence of residual static inter-qubit couplings leads to a rapid Gaussian decay of the fidelity. By applying randomly chosen Pauli matrices to the qubits at times j· Δ t (j∈ N) this fidelity decay was shown to be reducible to a linear-in-time exponential one [1]. In fact it was shown in [2] that with this method the error is certainly smaller than O( Δ t · T · k2) where k is the largest eigenvalue of the Hamiltonian describing the couplings. Using instead a deterministic decoupling sequence, applied periodically over multiples of the sequence time Tc, the error can be guaranteed to be smaller than O(T2 · k4 · Tc2). We present a method which combines the advantages of both methods and show that we can guarantee that the error will be smaller than O(T · Tc3 · k4), i.e. linear in time and fourth order in k.
On the other hand inter-qubit couplings are commonly used to generate two qubit gates in NMR quantum computation. We show how the recently introduced selective recoupling scheme of Yamaguchi et al. [3] can be stabilized by suited randomization against the accumulation of residual higher order average Hamiltonian theory errors.
[1] O. Kern, G. Alber, and D. L. Shepelyansky, Eur. Phys. J. D 32, 153 (2005)
[2] L. Viola and E. Knill, Phys. Rev. Lett. 94, 060502 (2005)
[3] F. Yamaguchi, T. D. Ladd, C. P. Master, Y. Yamamoto, and N. Khaneja, quant-ph/0411099.