Physicists at the Kastler Brossel Laboratory in Paris have succeeded in coupling a single collective atomic excitation to a nanoscale waveguide for the first time. The entangled state can be stored and subsequently read out with an external laser pulse as a guided single photon. The work could help in the development of the emerging field of waveguide quantum electrodynamics (QED), with applications in quantum networking, quantum nonlinear optics and quantum many-body physics.
Being able to integrate cold atoms with nanoscale waveguides could be important for making on-chip technologies for a future quantum internet. However, doing this is no easy task.
A team of researchers led by Julien Laurat has now generated and stored a single atomic excitation using an atomic register composed of a chain of laser-cooled caesium atoms tightly trapped along a nanoscale waveguide.
The waveguide has a diameter of just 400 nm, which means that a large fraction of light travels outside it in an evanescent field, focused along a length of 1 cm. This field allows 2000 cold atoms to be trapped around 200 nm from the nanofibre surface.
This stored collective entangled state can be efficiently read out with an external laser pulse, say the researchers.
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