Dissonance as a resource for probing the qubit depolarizing channel
Quantum channel identification, a standard problem in quantum metrology, is the task of estimating parameter(s) of a quantum channel. We investigate dissonance (quantum discord in the absence of entanglement) as an aid to quantum channel identification and find evidence for dissonance as a resource for quantum information processing. We consider the specific case of dissonant Bell-diagonal probes of the qubit depolarizing channel, using quantum Fisher information as a measure of statistical information extracted by the probe. In this setting dissonant quantum probes yield more statistical information about the depolarizing probability than do corresponding probes without dissonance and greater dissonance yields greater information. This effect only operates consistently when we control for classical correlation between the probe and its ancilla and the joint and marginal purities of the ancilla and probe.
Journal of Physics A: Mathematical and Theoretical
Frey, Michael R. and Yoder, Theodore J.. "Dissonance as a resource for probing the qubit depolarizing channel." Journal of Physics A: Mathematical and Theoretical (2012) : 385301.