Creating Decoherence-Free Subspaces with Strong and Fast Pulses

摘要

A decoherence-free subspace (DFS) isolates quantum information fromdeleterious environmental interactions. We give explicit sequences of strongand fast (``bang-bang'', BB) pulses that create the conditions allowing for theexistence of DFSs that support scalable, universal quantum computation. Onesuch example is the creation of the conditions for collective decoherence,wherein all system particles are coupled in an identical manner to theirenvironment. The BB pulses needed for this are generated using only theHeisenberg exchange interaction. In conjunction with previous results, thisshows that Heisenberg exchange is all by itself an enabler of universal faulttolerant quantum computation on DFSs.