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Deutsche Physikalische Gessellschaft IOP Institute of Physics

Implementation of universal control on a decoherence-free qubit

Evan M Fortunato1, Lorenza Viola2, Jonathan Hodges3, Grum Teklemariam4 and David G Cory1

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We demonstrate storage and manipulation of one qubit encoded into a decoherence-free subspace (DFS) of two nuclear spins using liquid state nuclear magnetic resonance techniques. The DFS is spanned by states that are unaffected by arbitrary collective phase noise. Encoding and decoding procedures reversibly map an arbitrary qubit state from a single data spin to the DFS and back. The implementation demonstrates the robustness of the DFS memory against engineered dephasing with arbitrary strength as well as a substantial increase in the amount of quantum information retained, relative to an un-encoded qubit, under both engineered and natural noise processes. In addition, a universal set of logical manipulations over the encoded qubit is also realized. Although intrinsic limitations prevent maintenance of full noise tolerance during quantum gates, we show how the use of dynamical control methods at the encoded level can ensure that computation is protected with finite distance. We demonstrate noise-tolerant control over a DFS qubit in the presence of engineered phase noise significantly stronger than observed from natural noise sources.


PACS

03.67.Lx Quantum computation architectures and implementations

33.25.+k Nuclear resonance and relaxation

03.65.-w Quantum mechanics

Subjects

Atomic and molecular physics

Computational physics

Quantum information and quantum mechanics

Dates

Issue 1 (February 2002)

Received 22 November 2001

Published 15 February 2002



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