Entanglement distillation

Distilling entanglement in continuous-variable systems

The distribution of entanglement lies at the heart of almost all quantum information and communication protocols. However, as a resource, entanglement is limited by its inherent fragility: loss and noise in the communication channel are highly detrimental. This decoherence can be overcome by increasing the amount of entanglement shared between communicating parties. Moreover, it is desirable to do so through local operations and classical communication (LOCC), in an efficient, scalable way. One such proposal is entanglement distillation: extracting an ensemble of strongly entangled states from a larger ensemble of weakly entangled states.

We are investigating the distillation of entanglement of the continuous variables (quadratures) of an optical field. Entanglement in these systems arises from non-classical correlations between photon statistics of two entangled optical modes. In contrast to discrete variable systems, the photon statistics of continuous variables depend on the optical phases of the modes. We have developed and characterised a number of tools to generate, manipulate and measure such states whilst preserving phase stability.