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Fault Tolerance with Noisy and Slow Measurements and Preparation

2010; American Physical Society; Volume: 105; Issue: 10 Linguagem: Inglês

10.1103/physrevlett.105.100501

1092-0145

Gerardo A. Paz-Silva, Gavin K. Brennen, J. Twamley,

Quantum and electron transport phenomena

It is not so well known that measurement-free quantum error correction protocols can be designed to achieve fault-tolerant quantum computing. Despite their potential advantages in terms of the relaxation of accuracy, speed, and addressing requirements, they have usually been overlooked since they are expected to yield a very bad threshold. We show that this is not the case. We design fault-tolerant circuits for the 9-qubit Bacon-Shor code and find an error threshold for unitary gates and preparation of p((p,g)thresh)=3.76×10(-5) (30% of the best known result for the same code using measurement) while admitting up to 1/3 error rates for measurements and allocating no constraints on measurement speed. We further show that demanding gate error rates sufficiently below the threshold pushes the preparation threshold up to p((p)thresh)=1/3.