We generalize past work on quantum sensor networks to show that, for d input parameters, entanglement can yield a factor O(d) improvement in mean squared error when estimating an analytic function of these parameters. We show that the protocol is optimal for qubit sensors, and conjecture an optimal protocol for photons passing through interferometers. Our protocol is also applicable to continuous variable measurements, such as one quadrature of a field operator. We outline a few potential applications, including calibration of laser operations in trapped ion quantum computing.

1 aQian, Kevin1 aEldredge, Zachary1 aGe, Wenchao1 aPagano, Guido1 aMonroe, Christopher1 aPorto, James, V.1 aGorshkov, Alexey, V. uhttps://arxiv.org/abs/1901.09042