



01995nas a2200205   4500008004100000245005100041210005100092260001300143490000700156520142000163100002001583700001901603700002301622700002401645700001801669700002301687700001701710700002501727856003701752       2013                        eng d00aQuantum Logic between Remote Quantum Registers0 aQuantum Logic between Remote Quantum Registers  c2013/2/60 v873 a  We analyze two approaches to quantum state transfer in solid-state spin
systems. First, we consider unpolarized spin-chains and extend previous
analysis to various experimentally relevant imperfections, including quenched
disorder, dynamical decoherence, and uncompensated long range coupling. In
finite-length chains, the interplay between disorder-induced localization and
decoherence yields a natural optimal channel fidelity, which we calculate.
Long-range dipolar couplings induce a finite intrinsic lifetime for the
mediating eigenmode; extensive numerical simulations of dipolar chains of
lengths up to L=12 show remarkably high fidelity despite these decay processes.
We further consider the extension of the protocol to bosonic systems of coupled
oscillators. Second, we introduce a quantum mirror based architecture for
universal quantum computing which exploits all of the spins in the system as
potential qubits. While this dramatically increases the number of qubits
available, the composite operations required to manipulate "dark" spin qubits
significantly raise the error threshold for robust operation. Finally, as an
example, we demonstrate that eigenmode-mediated state transfer can enable
robust long-range logic between spatially separated Nitrogen-Vacancy registers
in diamond; numerical simulations confirm that high fidelity gates are
achievable even in the presence of moderate disorder.
1 aYao, Norman, Y.1 aGong, Zhe-Xuan1 aLaumann, Chris, R.1 aBennett, Steven, D.1 aDuan, L., -M.1 aLukin, Mikhail, D.1 aJiang, Liang1 aGorshkov, Alexey, V.  uhttp://arxiv.org/abs/1206.0014v1