0603184v1

related topics
{states, state, optimal}
{entanglement, phys, rev}
{state, states, entangled}
{qubit, qubits, gate}
{error, code, errors}
{group, space, representation}
{cos, sin, state}

Completely positive covariant two-qubit quantum processes and optimal quantum NOT operations for entangled qubit pairs

J. Novotny, G. Alber, I. Jex

abstract: The structure of all completely positive quantum operations is investigated which transform pure two-qubit input states of a given degree of entanglement in a covariant way. Special cases thereof are quantum NOT operations which transform entangled pure two-qubit input states of a given degree of entanglement into orthogonal states in an optimal way. Based on our general analysis all covariant optimal two-qubit quantum NOT operations are determined. In particular, it is demonstrated that only in the case of maximally entangled input states these quantum NOT operations can be performed perfectly.

oai_identifier:
oai:arXiv.org:quant-ph/0603184
categories:
quant-ph
comments:
14 pages, 2 figures
doi:
10.1103/PhysRevA.73.062311
arxiv_id:
quant-ph/0603184
created:
2006-03-21

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