Yung, Man-Hong and Leung, Debbie W. and Bose, Sougato (2004) An exact effective two-qubit gate in a chain of three spins. Quantum Information and Computation, 4 (3). pp. 174-185. ISSN 1533-7146. http://resolver.caltech.edu/CaltechAUTHORS:20110818-153046301
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We show that an effective two-qubit gate can be obtained from the free evolution of three spins in a chain with nearest neighbor XY coupling, without local manipulations. This gate acts on the two remote spins and leaves the mediating spin unchanged. It can be used to perfectly transfer an arbitrary quantum state from the first spin to the last spin or to simultaneously communicate one classical bit in each direction. One ebit can be generated in half of the time for state transfer. For longer spin chains, we present methods to create or transfer entanglement between the two end spins in half of the time required for quantum state transfer, given tunable coupling strength and local magnetic field. We also examine imperfect state transfer through a homogeneous XY chain.
|Additional Information:||© 2004 Rinton Press. Received February 6, 2004; Revised May, 3, 2004. Communicated by: I. Cirac & C. Fuchs. We thank Andrew Landahl for help comments on an earlier manuscript. This work is partially supported from the US National Science Foundation under grant no. EIA-0086038. DWL thanks the Richard C. Tolman Endowment Fund at Caltech for partial support. SB thanks for a postdoctoral scholarship at the Caltech Institute for Quantum Information, during which this work started.|
|Subject Keywords:||spin chain; quantum gate; state transfer; entanglement|
|Classification Code:||PACS: 03.67.Mn,03.67.Hk,03.67.-a|
|Usage Policy:||No commercial reproduction, distribution, display or performance rights in this work are provided.|
|Deposited By:||Tony Diaz|
|Deposited On:||14 Oct 2011 18:09|
|Last Modified:||26 Dec 2012 13:29|
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