CPM Seminar

Multi-particle decoherence free subspaces and incoherently generated coherences

Raisa Karasik

Department of Physics
University of California, Berkeley

Decoherence often arises from the interaction between a quantum system and its environment and constitutes a major obstacle for quantum computation and information as it leads to destruction of fragile quantum states. Encoding into decoherence-free subspaces is one strategy to protect quantum states. The bad news is that we have found that decoherence-free subspaces do not exist for extended systems in more than one dimension for a broad class of realistic reservoirs, but the good news is that we have discovered that in some cases the dynamics of a quantum system can connive together with the environmental interactions to reduce decoherence. This property relies on the counterintuitive phenomenon of “incoherently generated coherences” and allows for identification of a new class of decoherence-free states. Examples of such systems are given from cavity quantum electrodynamics and squeezed light.