Dr. Robert Raussendorf, University of British Columbia
Quantum computation promises to solve certain
computational problems way more efficiently than is possible on a
classical computer. Shor's factoring algorithm breaking the RSA
cryptography system is a prime example. But quantum computation is also
fragile. Exotic quantum states are created in the process, exhibiting
entanglement among large number of particles across macroscopic distances. In
realistic > physical systems, decoherence acts to transform
these states into more classical ones, compromising their computational
power. Does decoherence put a fundamental limit to quantum
computation?
In theory it has been shown that it does not.
Decoherence can be counteracted by quantum error-correction, such that
if the strength of > quantum noise is below a critical level, then
arbitrarily long and accurate quantum computation is possible [1]. In my
talk, I first give a short introduction to the methods of quantum
error-correction. Subsequently, I will describe a realistic
architecture for fault-tolerant quantum computation, based on two-dimensional
arrays of qubits with only nearest-neighbor interaction [2].
This interaction > geometry is relevant for arrays of superconducting
qubits, optical > lattices and also for segmented ion traps. I will
further report on the recent experimental progress in realizing this
computational scheme [3,4,5].
[1] P. Aliferis, D. Gottesman, and J. Preskill,
Quantum Inf. Comput. *6*, 97 (2006).
[2] R. Raussendorf and J. Harrington, Phys. Rev.
Lett. *98, *190504 > (2007)
[3] Xing-Can Yao/et al. /Nature 482, 489 (2012). > [4] R. Barends /et al./ , Nature 508, 500 (2014). > > [5] J. Kelly /et al.,/ Nature *519*, 66-69 (2014)//
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