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Phys. Rev. A 64, 022301 (2001) [6 pages]

Complexity measure for continuous-time quantum algorithms

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D. Janzing* and Th. Beth
Institut für Algorithmen und Kognitive Systeme, Am Fasanengarten 3a, D-76 131 Karlsruhe, Germany

Received 12 October 2000; published 2 July 2001

We consider unitary dynamical evolutions on n qubits caused by time-dependent pair-interaction Hamiltonians and show that the running time of a parallelized two-qubit gate network simulating the evolution is given by the time integral over the chromatic index of the interaction graph. This defines complexity measures of continuous and discrete quantum algorithms, which are in exact one-to-one correspondence. We prove a lower bound on the complexity of those multiparticle states, which show quantum superpositions on the macroscopic scale.

© 2001 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevA.64.022301
DOI:
10.1103/PhysRevA.64.022301
PACS:
03.67.Lx, 03.65.Ta

*Electronic address: janzing@ira.uka.de