



01192nas a2200145   4500008004100000245007300041210006900114260001500183520071800198100002200916700002300938700002400961700002500985856003601010       2018                        eng d00aOptimal and Secure Measurement Protocols for Quantum Sensor Networks0 aOptimal and Secure Measurement Protocols for Quantum Sensor Netw  c2018/03/233 a<p>Studies of quantum metrology have shown that the use of many-body entangled states can lead to an enhancement in sensitivity when compared to product states. In this paper, we quantify the metrological advantage of entanglement in a setting where the quantity to be measured is a linear function of parameters coupled to each qubit individually. We first generalize the Heisenberg limit to the measurement of non-local observables in a quantum network, deriving a bound based on the multi-parameter quantum Fisher information. We then propose a protocol that can make use of GHZ states or spin-squeezed states, and show that in the case of GHZ states the procedure is optimal, i.e., it saturates our bound.</p>1 aEldredge, Zachary1 aFoss-Feig, Michael1 aRolston, Steven, L.1 aGorshkov, Alexey, V.  uhttp://arxiv.org/abs/1607.04646