28p-R-11 Reversible Unsharp Measurement in Quantum Optics

Paul Busch

Paul Busch, Javed Singh

Ayan Barui, Mayukha Pal, Prasanta Kumar Panigrahi

Masato Koashi, Masahito Ueda

We consider a probabilistic reversing operation that returns the measured system to its original state by means of a physical process, and derive a trade-off relation between the unsharpness of the measurement and the best efficiency of the reversing operation. Such a reversing operation is shown to serve as a probabilistic quantum error correction, which will be useful when the numbers of qubits and gate operations are limited.

Stig Stenholm

Paul Busch

The Einstein-Podolsky-Rosen (EPR) reality criterion is generalized to fit with the notion of positive-operator-valued observables occurring in quantum optics, stochastic quantum mechanics, and other fields of quantum physics. The resulting concept of unsharp reality for quantum systems is illustrated within stochastic spin space where it leads to a notion of unsharp spin property. Finally we investigate the possibility of joint spin measurements and give a brief discussion of the EPR-Bell argument for unsharp spin properties.