  Quantum computers are poised to radically outperform their classical
counterparts by manipulating coherent quantum systems. A realistic quantum
computer will experience errors due to the environment and imperfect control.
When these errors are even partially coherent, they present a major obstacle to
achieving robust computation. Here, we propose a method for introducing
independent random single-qubit gates into the logical circuit in such a way
that the effective logical circuit remains unchanged. We prove that this
randomization tailors the noise into stochastic Pauli errors, leading to
dramatic reductions in worst-case and cumulative error rates, while introducing
little or no experimental overhead. Moreover we prove that our technique is
robust to variation in the errors over the gate sets and numerically illustrate
the dramatic reductions in worst-case error that are achievable. Given such
tailored noise, gates with significantly lower fidelity are sufficient to
achieve fault-tolerant quantum computation, and, importantly, the worst case
error rate of the tailored noise can be directly and efficiently measured
through randomized benchmarking experiments. Remarkably, our method enables the
realization of fault-tolerant quantum computation under the error rates
observed in recent experiments.
