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Quantum information processing requires a system in which a single photon controls a single atom and vice versa. Here, the authors demonstrate such reciprocal operation and achieve coherent manipulation of a quantum dot by a few photons sent on an optical cavity.

The interaction between single spins and mechanical motion has been demonstrated in solid-state platforms, though limited to low-frequency modes. Here, the authors realize the coupling between an electron spin in a double quantum dot and a high-frequency mechanical mode in a suspended carbon nanotube device.

A single photon with near-unity indistinguishability is generated from quantum dots in electrically controlled cavity structures. The cavity allows for efficient photon collection while application of an electrical bias cancels charge noise effects.

Mechanisms of distinct resonance in microcavities driven by strongly detuned single quantum dots are not well understood. Investigation of non-resonant dot–cavity coupling of individual quantum dots in micropillars now suggests a dominant role of phonon-mediated dephasing. This new perspective may have implications for single-photon sources, quantum information applications and spectroscopy.

An optical non-linearity at the single-photon level is reported with a semiconductor quantum dot–cavity device. The device performs as an efficient single-photon filter that strongly suppresses the multiphoton components of incident coherent pulses.

The Mollow triplet, originally observed in the fluorescence spectrum of an optically excited two level system, is a signature of quantum electrodynamics. Here, the authors observe its phononic equivalent by magnetically coupling a single nitrogen-vacancy qubit to the vibrations of a silicon carbide nanowire.

Coupling of the electronic states in a quantum dot and the vibrations in a nanowire can be achieved by using strain.

A three-partite cluster state made of one semiconductor spin and two indistinguishable photons is generated from an InGaAs quantum dot embedded in a pillar microcavity. The three-partite entanglement rate is 0.53 MHz at the output of the device.

A photon-number Bell state is generated from a quantum dot by controlling the light–matter entanglement during spontaneous emission. This excitation protocol can be scaled up by using N consecutive π-pulses to deliver multimode photonic entanglement.

Following excitation with a resonant laser, on-demand generation of non-classical light states in photon-number superpositions of zero-, one- and two-photon Fock states is demonstrated from a GaAs-based cavity containing InAs quantum dots.

Optical readout techniques for nanomechanical force probes usually generate more heat than what can be dissipated through the nanoresonators. Here, the authors use an interferometric readout scheme, achieving large force sensitivity using suspended silicon carbide nanowires at dilution temperatures.

In classical thermodynamics irreversibility occurs whenever a non-thermal system is brought into contact with a thermal environment. Using quantum trajectories the authors here establish two energetic footprints of quantum irreversible processes, and find that while quantum irreversibility leads to the occurrence of a quantum heat and a reduction of work production, the two are not linked in the same manner as the classical laws of thermodynamics would dictate.