TY - JOUR T1 - Direct Fidelity Estimation from Few Pauli Measurements JF - Physical Review Letters Y1 - 2011 A1 - Steven T. Flammia A1 - Yi-Kai Liu AB - We describe a simple method for certifying that an experimental device prepares a desired quantum state rho. Our method is applicable to any pure state rho, and it provides an estimate of the fidelity between rho and the actual (arbitrary) state in the lab, up to a constant additive error. The method requires measuring only a constant number of Pauli expectation values, selected at random according to an importance-weighting rule. Our method is faster than full tomography by a factor of d, the dimension of the state space, and extends easily and naturally to quantum channels. VL - 106 UR - http://arxiv.org/abs/1104.4695v3 CP - 23 J1 - Phys. Rev. Lett. U5 - 10.1103/PhysRevLett.106.230501 ER -