Universal quantum computation under asymmetric quantum error correction
Ashley M. Stephens, Zachary W. E. Evans, Simon J. Devitt, Lloyd C. L. Hollenberg · arXiv (Cornell University) · 2007
In many physical systems it is expected that environmental decoherence will induce an asymmetry between dephasing and relaxation that will result in qubits experiencing discrete phase errors more frequently than discrete bit errors. In the presence of such an asymmetry, an appropriately asymmetric quantum code - that is, a code that can correct more phase errors than bit errors - will be more efficient than a traditional, symmetric quantum code. However, it has not yet been shown that such a code is suitable for universal fault tolerant quantum computation. Here we construct fault tolerant circuits to convert between an asymmetric subsystem code and a symmetric subsystem code. We show that, for a large error asymmetry, the failure rate of sections of a logical circuit can be reduced by up to two orders of magnitude by converting to an asymmetric code and that doing so does not preclude universality.