Efficient Fault-Tolerant Quantum Computing
Martin Suchara, AT&T Labs Research
Quantum error correction presents some of the most significant and interesting challenges that must be resolved before building an efficient quantum computer. Quantum error correcting codes allow to successfully run quantum algorithms on unreliable quantum hardware. Because quantum hardware suffers from errors such as decoherence, leakage or qubit loss, and these errors corrupt delicate quantum states rather than binary information, the known error correction techniques are complex and have a high overhead.
In my talk I first introduce the two main families of quantum error correcting codes and quantify their overhead using specific examples of algorithms and hardware technologies. Then I describe several new techniques that I developed to reduce this overhead. For example, the maximum likelihood decoder (MLD) is an efficient algorithm that finds the recovery operation that maximizes the probability of a successful error correction given the observed error syndrome. Numerical simulations of the MLD algorithm for physical error rates around 10% showed a 100 fold reduction of the logical error probability compared to earlier techniques. I also show new designs of error correcting codes that are tailored to work more efficiently with the constraints of specific physical technologies.