Abstract:

Coherent control of quantum systems rely upon the presence of coherence, loss of which ("decoherence") results in marked decrease in controllability. This issue is of significant interest also in the subject of quantum computation. There are several techniques either to avoid or to eliminate decoherence. Those techniques demand either certain symmetry in the system Hamiltonian or severe technical challenges in implementing them. In this talk, I will discuss a more general approach which can combat the above two issues. This approach is quite fundamental and relies on quantum interferences between overlapping resonances.

We demonstrate this technique by considering a system comprising spin-half particles interacting with a bosonic thermal bath. In presence of overlapping resonances, decoherence of the spin-system can be minimized by choosing in an optimal way an initial superposition of the spin states. We show the results for an available spin-boson system, namely, Cooper-pair qubits interacting with a nano-mechanical oscillator.