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Photons emitted from a quantum dot typically have slightly different frequencies owing to various sources of noise. Here, the authors suppress the noise, notably the noise arising from the nuclear spins, and demonstrate single-photon emission with a transform-limited optical linewidth.

Charge noise and spin noise lead to decoherence of the state of a quantum dot. A fast spectroscopic technique based on resonance fluorescence can distinguish between these two deleterious effects, enabling a better understanding of how to minimize their influence.

The ability to imprint phase shifts on light lie at the basis of several classical and quantum light-based information processing primitives. Here, the authors demonstrate the phase shift of an optical field by a single quantum emitter in a waveguide, at the single photon level.

Nano-NMR techniques are used on a semiconductor quantum dot to reveal an electron-mediated coupling between nuclear spins.

Electronic excitations in low-dimensional quantum nanoelectronic devices are collective waves that are strongly affected by the Coulomb interaction. Here, the authors demonstrate that they are able to prepare these collective excitations down to the single electron level and control their propagation.

Resonantly-excited quantum-dot-based single photon sources feature very high purity, but also limited efficiency due to the need to suppress the residual pump. Here, the authors demonstrate a workaround, performing optical pumping and signal collection in two orthogonal modes inside a nanophotonic circuit.

The spin state of a single electron is shown to control the transmission of single photons through a nanophotonic waveguide, thus realizing a spin-based photonic switch.

Gate-defined quantum dots offer a way to engineer electrically controllable quantum systems with potential for information processing. Here, the authors transfer angular momentum from the polarization of a single photon to the spin of a single electron in a gate-defined double quantum dot.

Adding tunable photon-photon nonlinearities to programmable photonic circuits would greatly extend their capabilities. Here, the authors demonstrate this by embedding a photonic-crystal waveguide nanostructure hosting an InAs quantum dot within a programmable linear optical circuit, and using it to realise a proof-of-concept quantum simulation of anharmonic molecular vibrational dynamics.

Coherent control of plasmon wavepackets is essential for quantum information processing using flying electron qubits. Here, the authors demonstrate a method to isolate and select electron channels contributing to a plasmon using a cavity formed by local constrictions, enabling precise control of plasmon eigenstates.

Fusion-based quantum computing relies on small entangled resource states that are then fused together probabilistically via linear optical circuits. Here, the authors demonstrate temporal fusion—where resource states generated at different times by the same quantum emitter are fused together—using a spin-photon interface in a quantum dot embedded in a photonic crystal waveguide.

Spin–photon interfaces provide a connection between quantum information stored in atomic or electronic spins and optical communications networks. A quantum photon emitter with long-lived, controllable coherent spin has now been demonstrated.

A spatial resolution of 30 nm (=λ/31) exceeding the diffraction limit is achieved by super-resolution fluorescence microscopy. The nanoscopic imaging scheme can be applied to coherent quantum-mechanical systems such as quantum dots, as well as colour centres.

The emergence of universal collective behaviour is demonstrated through collisions of electron droplets containing up to five particles, which exhibit strong all-body correlations characteristic of a Coulomb liquid.

The development of electronic flying qubits requires the ability to generate and control single-electron excitations. Here the authors demonstrate quantum coherence of ultrashort single-electron plasmonic pulses in an electronic Mach-Zehnder interferometer, revealing a non-adiabatic regime at high frequencies.

Nuclear magnetic resonance experiments on 100,000 nuclear spins in a quantum dot allows for the reversal of these spins back and forth as if they were a single unit.

High efficiency, coherence and indistinguishability are key requirements for the application of single-photon sources for quantum technologies, but hard to achieve concurrently. A gated quantum dot in an open, tunable microcavity now can create single photons on-demand with an end-to-end efficiency of 57%, preserving coherence over microsecond-long trains of single photons.

In a radiative Auger process, an excited electron relaxes by concomitant emission of a redshifted photon and energy transfer to another electron. Measuring radiative Auger processes in a quantum dot with single-photon resolution enables determination of the energy of single-electron levels as well as their lifetimes.

Realising scalable entangled photon sources with quantum dots requires compensating for both wavelength mismatches and exciton fine-structure splitting (FSS). So far, multiple QDs with the same emission wavelength and near-zero FSS have not been demonstrated. Here, the authors fill this gap, reaching high entanglement fidelity for multiple QDs tuned into resonance with each other or with Rb atoms.

Quantum bits defined in an Aharonov–Bohm ring are transported over long distances while being controlled with electric fields.

Coherent manipulation of hole-orbital states in semiconductor quantum dots is achieved through stimulated Auger processes, opening doors to new types of orbital-based solid-state quantum photonic devices.

Coherent population-trapping studies of a single hole spin in quantum dot field-effect devices with low charge-noise performance provide insight into the anisotropy of the hole hyperfine interaction between hole and nuclear spins.

Coupling a single-photon emitter to a mechanical resonator enables the generation of single phonons. Here, the authors study the interaction of a single-photon emitter and a phononic-crystal resonator in the sideband-resolved regime.

Measurements on a single artificial atom—a quantum dot—coupled to an optical cavity show scattering dynamics that depend on the number of photons involved in the light–matter interaction, which is a signature of stimulated emission.

A semiconductor quantum dot can passively mediate interactions between two photons, enabling the creation of entangled photon states.

Entanglement between single photons and solid-state emitters is a key component for photonic quantum computing and networks. Here, using a single electron spin in a quantum dot, the authors present a deterministic photon source achieving three-qubit entanglement of one electron spin and two photons.

Collisions between two individual electrons in a quantum nanoelectronic circuit revealed a mutual interaction fully mediated by Coulomb repulsion—an essential building block for two-qubit logic implementations with flying electrons.

Single-shot readout of optically active spin qubits is typically limited by low photon collection rates and measurement back-action. Here the authors overcome these limitations by using an open cavity approach for single-shot readout of a semiconductor quantum dot and demonstrate record readout time of a few ns.

Radiative Auger is a process that leads to a red-shift of the optical emission of an atom or a charged solid-state quantum emitter. Here, the authors realize the inverse process by optically driving the radiative Auger transition of a short-lived electronic state in a semiconductor quantum dot.

GaAs quantum dots emitting at the near-red part of the spectrum usually suffers from excess charge-noise. With a careful design of a n-i-p-diode structure hosting GaAs quantum dots, the authors demonstrate ultralow-noise behaviour and high-fidelity spin initialisation close to rubidium wavelengths.

The exchange interaction between spins poses considerable challenges for high-fidelity control of semiconductor spin qubits. Here, the authors use pulse optimization and closed-loop control to achieve a gate fidelity of 99.5% for exchange-based single-qubit gates of two-electron spin qubits in GaAs.

Manipulation of multiple connected quantum objects is mandatory for any scalable quantum information platform. Based on finely tuned virtual gate control, the integration of nearest-neighbour coupled semiconductor quantum dots in a 3 × 3 array enables 2D coherent spin control.

Surface acoustic waves are promising candidates to convey flying qubits through semiconductor circuits. The authors investigate the central building block of such a circuit in an experiment and present a route to realise quantum logic gates with flying electrons that are surfing on a sound-wave.

On-chip, long-distance entanglement of spin qubits in semiconductors could enable connectivity of quantum core units for networked quantum computing. The moving trapping potential of a surface acoustic wave can subsequently displace two entangled spins while preserving entanglement over a separation of 6 μm.

The existence of the Kondo cloud is revealed by the spatially resolved characterization of the oscillations of the Kondo temperature in a Fabry–Pérot interferometer and its extent is shown to be several micrometres.

Phase modifications take place in electron transport through quantum dots, yet the details are not agreed between theory and experimental observations to date. Edlbauer et al. confirm the theory by scanning fourteen consecutive resonant states of a large quantum dot hosting hundreds of electrons.

Strong coupling between a gated semiconductor quantum dot and an optical microcavity is observed in an ultralow-loss frequency-tunable microcavity device.