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arXiv · 1504.03772

Continuous decomposition of quantum measurements via Hamiltonian feedback

Jan Florjanczyk·Todd A. Brun
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Abstract

We characterize the set of generalized quantum measurements that can be decomposed into a continuous measurement process using a stream of probe qubits and a tunable interaction Hamilto- nian. Each probe in the stream interacts weakly with the target quantum system, then is measured projectively in a standard basis. This measurement result is used in a closed feedback loop to tune the interaction Hamiltonian for the next probe. The resulting evolution is a stochastic process with the structure of a one-dimensional random walk. To maintain this structure, and require that at long times the measurement outcomes be independent of the path, the allowed interaction Hamil- tonians must lie in a restricted set, such that the Hamiltonian terms on the target system form a finite dimensional Jordan algebra. This algebraic structure of the interaction Hamiltonians yields a large class of generalized measurements that can be continuously performed by our scheme, and we fully describe this set.

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Jan Florjanczyk, Todd A. Brun. 2015-04-15. Continuous decomposition of quantum measurements via Hamiltonian feedback. https://doi.org/10.1103/physreva.92.062113

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