Physicists at C2N have demonstrated for the first time the direct generation of light in a state that is simultaneously a single photon, two photons, and no photon at all. They showed that the same kind of light emitter used for decades is also able to generate these quantum states, and expect that this holds true for any kind of atomic system.
The strong-coupling regime of cavity quantum electrodynamics (QED) represents the light–matter interaction at the fully quantum level, for instance, a single photon shifts the resonance frequencies significantly. However, miniaturizing semiconductor cavities without introducing charge noise and scattering losses remained a challenge. Here we present a gated, ultralow-loss, frequency-tunable quantum-dot microcavity device in the strong coupling limit overcoming all of the mentioned shortcomings.
Semiconductor quantum dots offer the highest rate and quality of single photons among all other solid-state quantum light sources. However, they lack access to a long-lived quantum memory, such as a proximal nuclear spin, that would make them competitive for large-scale quantum architectures. Gangloff et al. used the spin of a single electron and light to cool an ensemble of about 30,000 nuclei within semiconductor quantum dots. They then extended this approach to manipulate individual nuclear spins. The ability to manipulate the ensemble of nuclei coherently, down to the single nuclear spin, could lead to the realization of a quantum dot network where each node has its own dedicated quantum memory.