Waveguide-QED with Rydberg atoms

Lead Research Organisation: University College London
Department Name: London Centre for Nanotechnology


The interaction of matter and light confined within cavities (cavity QED), has a long and fruitful history achieving a number of high precision tests of quantum theory and more recently a platform for the manipulation of quantum information. In recent times a related area of research, waveguide QED, has attracted significant attention. Waveguide-QED is centred around the coupling of atoms (real or artificial) to a continuum of electromagnetic modes constrained to prop- agate in a single dimension. Moving from cavities to a 1D continuum presents opportunities which may be exploited for quantum information processing. The atoms can have a significant effect on photon transport properties through the waveguide. This has lead to potential uses in photon routing and the generation of non-classical light e.g bunching and anti bunching. The waveguide may also act to mediate long range interactions between atoms. Due to the spontaneous emission being confined to a single dimension the interaction strength does not decay with distance as is the case for atoms in free space. By placing atoms at positions of identical electric field within the mode the atoms can col- lectively interact with the continuum as if they were a single entity, a situation described by the Dicke Hamiltonian. This leads to super/sub-radiance, where spontaneous emission is strongly enhanced or suppressed respectively. Sub- radiant states in particular are of interest for quantum information processing. Their highly suppressed interaction with the waveguide is due to interference effects forbidding them to decay. The sub-radiant states form a decoherence-free subspace (DFS), a partition of the total atomic Hamiltonian which is decoupled from the environment. In this project high-n Rydberg states in helium will be used to explore waveguide-QED phenomenon. Rydberg atoms are ideally suited to this task due to their exaggerated properties, such as large transition dipole moments and, particularly in circular states, extended lifetimes. The wide range of transition frequencies makes them a flexible technology capable of coupling to a wide range of other quantum computing systems which operate in the GHz region, in particular super-conducting qubits. Initial studies will be performed in 3D waveguide structures before transitioning to co-planar waveg- uides. Realising waveguide-QED phenomena in co-planar waveguide structures would represent a large step towards hybrid quantum computing schemes with Rydberg atoms.


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Studentship Projects

Project Reference Relationship Related To Start End Student Name
EP/P510270/1 31/03/2016 30/08/2022
1927649 Studentship EP/P510270/1 17/09/2017 17/12/2021 Jake David Tommey