Regensburg 2013 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 37: Quantum Coherence, Quantum Information Systems 1
TT 37.12: Vortrag
Mittwoch, 13. März 2013, 12:30–12:45, H19
Dynamic Generation of Thermally Stable Surface Code — •Daniel Becker1, Tetsufumi Tanamoto2, Adrian Hutter1, Fabio Pedrocchi1, and Daniel Loss1 — 1Department of Physics, University of Basel, Klingelbergstrasse 82, CH-4056 Basel, Switzerland — 2Corporate R & D center, Toshiba Corporation, Saiwai-ku, Kawasaki 212-8582, Japan
Quantum memories that are based on surface codes with local qubit interactions such as Kitaev’s toric code are vulnerable to thermal fluctuations. By inducing strongly non-local interactions between the qubits via a coupling to, e.g, cavity modes [1] or the spins of a ferromagnet [2], the lifetime of encoded states in the presence of a thermal environment increases exponentially with the code’s size. We propose a scheme to dynamically realize such a stable quantum memory based on the toric code for qubit systems with typical two-body interactions (Ising, XY, Heisenberg), using periodic, NMR-like pulse sequences. It allows both to prepare codewords without measurements and to protect them dynamically against the time evolution of the physical qubit system. Thermal stability is achieved by weakly coupling the qubits to an additional cavity mode. We investigate how the fidelity, with which the toric code is realized, depends on the period length T of the pulse sequence and the magnitude of possible pulse errors. This allows to optimize tunable system parameters, such as T, in the presence of pulse errors and decoherence.
[1] F. Pedrocchi et al., Phys. Rev. B 83, 115415 (2011)
[2] F. Pedrocchi et al., arXiv:1209.5289