114 research outputs found
Direct Fidelity Estimation from Few Pauli Measurements
We describe a simple method for certifying that an experimental device prepares a desired quantum state ρ. Our method is applicable to any pure state ρ, and it provides an estimate of the fidelity between ρ 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
The Optical Frequency Comb as a One-Way Quantum Computer
In the one-way model of quantum computing, quantum algorithms are implemented
using only measurements on an entangled initial state. Much of the hard work is
done up-front when creating this universal resource, known as a cluster state,
on which the measurements are made. Here we detail a new proposal for a
scalable method of creating cluster states using only a single multimode
optical parametric oscillator (OPO). The method generates a continuous-variable
cluster state that is universal for quantum computation and encoded in the
quadratures of the optical frequency comb of the OPO. This work expands on the
presentation in Phys. Rev. Lett. 101, 130501 (2008).Comment: 20 pages, 8 figures. v2 corrects minor error in published versio
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