TY - JOUR T1 - Optimal Pure-State Qubit Tomography via Sequential Weak Measurements JF - Phys. Rev. Lett. Y1 - 2018 A1 - Ezad Shojaee A1 - Christopher S. Jackson A1 - Carlos A. Riofrio A1 - Amir Kalev A1 - Ivan H. Deutsch AB -

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.

VL - 121 UR - https://arxiv.org/abs/1805.01012 CP - 130404 U5 - https://doi.org/10.1103/PhysRevLett.121.130404 ER -