Optimal Pure-State Qubit Tomography via Sequential Weak Measurements

TitleOptimal Pure-State Qubit Tomography via Sequential Weak Measurements
Publication TypeJournal Article
Year of Publication2018
AuthorsShojaee, E, Jackson, CS, Riofrio, CA, Kalev, A, Deutsch, IH
JournalPhys. Rev. Lett.
Volume121
Issue130404
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.

URLhttps://arxiv.org/abs/1805.01012
DOI10.1103/PhysRevLett.121.130404