Month: September 2008

Quantum Parallelism as a Tool for Ensemble Spin Dynamics Calculations | Phys. Rev. Lett. 101, 120503 (2008)

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Quantum Parallelism as a Tool for Ensemble Spin Dynamics Calculations

Gonzalo A. Álvarez1,*, Ernesto P. Danieli2, Patricia R. Levstein1, and Horacio M. Pastawski1,†

1Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina

2ITMC, RWTH Aachen University, D-52074 Aachen, Germany

Received 19 October 2007; published 19 September 2008

Efficient simulations of quantum evolutions of spin-1/2 systems are relevant for ensemble quantum computation as well as in typical NMR experiments. We propose an efficient method to calculate the dynamics of an observable provided that the initial excitation is “local.” It resorts to a single entangled pure initial state built as a superposition, with random phases, of the pure elements that compose the mixture. This ensures self-averaging of any observable, drastically reducing the calculation time. The procedure is tested for two representative systems: a spin star (cluster with random long range interactions) and a spin ladder.

© 2008 The American Physical Society

via Phys. Rev. Lett. 101, 120503 (2008): Quantum Parallelism as a Tool for Ensemble Spin Dynamics Calculations.

Schemes of the quantum evolution of an ensemble (panel (a)) and a pure-state (panel (b)). Each |phi_i> is a simple tensor product state. Both observable dynamics are indistinguishable  for large Hilbert spaces.
Schemes of the quantum evolution of an ensemble (panel (a)) and a pure-state (panel (b)). Each |phi_i> is a simple tensor product state. Both observable dynamics are indistinguishable for large Hilbert spaces.
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