Fibonacci scheme for fault-tolerant quantum computation

We rigorously analyze Knill’s Fibonacci scheme for fault-tolerant quantum computation, which is based on the recursive preparation of Bell states protected by a concatenated error-detecting code. We prove lower bounds on the threshold fault rate of 0.67 10−3 for adversarial local stochastic noise, and 1.25 10−3 for independent depolarizing noise. In contrast to other schemes with comparable proved accuracy thresholds, the Fibonacci scheme has a significantly reduced overhead cost because it uses postselection far more sparingly.