Characterisation of quantum channels in plasmonic metamaterials and bulk optical systems.

Abstract

Quantum channels are key to our understanding of how quantum information can be processed and transmitted. In this respect, over the past decade light has become an important carrier of quantum information. More recently, metamaterials have opened up many new exciting ways of controlling and manipulating light in the quantum regime, and in particular, controlling the polarisation and orbital angular momentum of light. In this work, we undertake an indepth characterisation of quantum channels made from plasmonic metamaterials and bulk optical systems by probing them with quantum states of light. We rst experimentally demonstrate the active control of a plasmonic metamaterial operating in the quantum regime. Using an external laser, we control the temperature of the metamaterial and carry out quantum process tomography on single-photon polarization-encoded qubits sent through, characterizing the metamaterial as a variable quantum channel. We nd that the overall polarization response can be tuned by up to 33%. Second, we experimentally realise a more complicated type of quantum channel in the form of a non-Markovian process made from the sum of two Markovian processes, and a Markovian process from two non-Markovian processes in a comparable bulk optical system. We perform quantum process tomography, and obtain high process delities. We discuss how these more complex types of quantum channel may be implemented using metamaterials.