Quantum instrument

A quantum instrument is a quantum operation with both classical and quantum outputs. It combines the concepts of measurement and quantum operation.

Description

Usually it is implemented as a weighted collection of completely positive maps the sum of which is trace preserving.

Quantum Instrument: collection $\mathcal{E}_k$ acts as: $\rho^{AB} \rightarrow \tilde{\rho}^{AA'B} := \sum_k \mathcal{E}_k \left( \rho^{AB} \right)\otimes \vert k \rangle \langle k\vert^{A'}$

A quantum instrument is more general than a quantum operation because it records the outcome k of which operator acted on the state.

References

This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. Please improve this article by introducing more precise citations. (July 2009)

E. Davies, J. Lewis. An operational approach to quantum probability, Comm. Math. Phys., vol. 17, pp. 239-260, 1970.
Distillation of secret key paper
Another paper which uses the concept

Last modified on 8 January 2013, at 23:31