Universal fault-tolerant adiabatic quantum computing with quantum dots or donors

Daniel A. Lidar

Robin Blume-Kohout

Dave Bacon, Julia Kempe, Daniel A. Lidar +1 more

A general scheme to perform universal, fault-tolerant quantum computation within decoherence-free subspaces (DFSs) is presented. At most two-qubit interactions are required, and the system remains within the DFS throughout the entire implementation of a quantum gate. We show explicitly how to perform universal computation on clusters of the four-qubit DFS encoding one logical qubit each under spatially symmetric (collective) decoherence. Our results have immediate relevance to quantum computer implementations in which quantum logic is implemented through exchange interactions, such as the recently proposed spin-spin coupled quantum dot arrays and donor-atom arrays.

Ari Mizel

Quantum computation has revolutionary potential for speeding computational tasks such as factoring and simulating quantum systems, but the task of constructing a quantum computer is daunting. Adiabatic quantum computation and other ``hands-off approaches relieve the need for rapid, precise pulsing to control the system, inspiring at least one high-profile effort to realize a hands-off quantum computing device. But is hands-off incompatible with fault-tolerant? Concerted effort and many innovative ideas have not resolved this question but have instead deepened it, linking it to fundamental problems in quantum complexity theory. Here we present a hands-off approach that is provably (a) capable of scalable universal quantum computation in a non-degenerate ground state and (b) fault-tolerant against an analogue of the usual local stochastic fault model. A satisfying physical and numerical argument indicates that (c) it is also fault-tolerant against thermal excitation below a threshold temperature independent of the computation size.

I. S. Osborne

Yasunari Suzuki