Abstract

The spin-coherent-state positive-operator-valued-measure (POVM) is a fundamental measurement in quantum science, with applications including tomography, metrology, teleportation, benchmarking, and measurement of Husimi phase space probabilities. We prove that this POVM is achieved by collectively measuring the spin projection of an ensemble of qubits weakly and isotropically. We apply this in the context of optimal tomography of pure qubits. We show numerically that through a sequence of weak measurements of random directions of the collective spin component, sampled discretely or in a continuous measurement with random controls, one can approach the optimal bound.

Date

September 28, 2018

Authors

Ezad Shojaee, Christopher S Jackson, Carlos A Riofrío, Amir Kalev, Ivan H Deutsch

Journal

Physical review letters

Volume

121

Issue

13

Pages

130404

Publisher

American Physical Society