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Concurrence of a 2-Qubit System
Author

Mark S. Tame
Organization: Queen's Quantum Technology Group
Department: Dept. of Applied Mathematics and Theoretical Physics
URL: http://www.am.qub.ac.uk/users/m.tame/index.html
Revision date

2006-06-18
Description

When analysing quantum systems in Quantum Information Theory it is sometimes necessary to compute the amount of entanglement that exists between two qubits. For example, suppose Alice and Bob share a pair of entangled qubits described by a density matrix. If we would like to determine the amount of entanglement present between the two qubits, then the concurrence represents a measure of entanglement that can be used [1]. However, it becomes quite a task to calculate the concurrence for a complicated matrix if we would like to see how the entanglement changes as a particular parameter is varied. This parameter could describe imperfections in the ideal case, such as decoherence acting on the system, with the density matrix losing purity as the parameter increases. Calculating the concurrence by hand in this case becomes unmanageable. What the Concurrence function does, is allow you to do this by letting Mathematica do the work for you.

[1] W. K. Wooters, Phys. Rev. Lett. 80, 2245 (1998).
Subject

*Science > Physics > Quantum Physics
Keywords

Quantum Information, Entanglement, Qubit, Concurrence, Density matrix, 2 qubits, two qubits
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Concurrence.nb (65.2 KB) - Mathematica Notebook [for Mathematica 5.0]