  Quantum photonics holds great promise for future technologies such as secure
communication, quantum computation, quantum simulation, and quantum metrology.
An outstanding challenge for quantum photonics is to develop scalable miniature
circuits that integrate single-photon sources, linear optical components, and
detectors on a chip. Plasmonic nanocircuits will play essential roles in such
developments. Plasmonic components feature ultracompact geometries and can be
controlled more flexibly and more energy-efficiently compared to conventional
dielectric components due to strong field confinement and enhancement.
Moreover, plasmonic components are compatible with electronic circuits, thanks
to their deep subwavelength sizes as well as their electrically conducting
materials. However, for quantum plasmonic circuits, integration of stable,
bright, and narrow-band single photon sources in the structure has so far not
been reported. Here we present a quantum plasmonic nanocircuit driven by a
self-assembled GaAs quantum dot. The quantum dot efficiently excites
narrow-band single plasmons that are guided in a two-wire transmission line
until they are converted into single photons by an optical antenna. Our work
demonstrates the feasibility of fully on-chip plasmonic nanocircuits for
quantum optical applications.
