Plasmonic nanostructures from crystalline silver for ultrafast quantum photonics

Metal-based nanostructures made from low-loss plasmonic materials allow a targeted and strong enhancement of light-matter interaction in a broad wavelength range. As a result, the far-field single-photon emission rates from solid-state quantum defects can overcome both the rate of dipole dephasing and that of plasmon absorption in metals. This approach promises the advent of single-photon sources featuring bitrates up to the THz range and operating at cryogen-free temperatures. We establish simple and intuitive fundamental enhancement limits for plasmonic systems coupled to quantum emitters and present practical methods for achieving these advantageous regimes.