Single Photons on Silicon express
Tiny semiconductor islands grown right on silicon fire off single photons, like a machine gun that shoots exactly one bullet at a time. These islands are called quantum dots. They can emit light in discrete packets, which is needed for secure information in quantum networks. But until now, they have been difficult to integrate with silicon electronics and to make work at not-too-low temperatures.
In the new work, quantum dots made of indium gallium arsenide were placed in ring resonators — structures that gather light into a narrow beam, like a mirrored well. Each dot can be tuned with an electric field: voltage shifts the emission color by about 16 nanometers, like switching radio stations without touching the transmitter itself. At the same time, the purity of single photons remains high: the probability of emitting two photons at once is less than one percent.
Such sources can be placed side by side on a single chip and tuned to the same wavelength so that photons from different dots are indistinguishable. This paves the way for quantum repeaters and secure communication over ordinary fiber-optic lines.
Original abstract
as written by the authors arXiv:2604.23422
Semiconductor quantum dots (QDs) offer outstanding quantum-optical properties, making them highly attractive for quantum information technologies. However, combining wide-range electrical tunability, efficient photon extraction, elevated-temperature operation, monolithic silicon integration, and telecom-wavelength compatibility remains a major challenge. Here, we demonstrate electrically contacted circular Bragg grating (eCBG) resonators incorporating InGaAs QDs directly grown on silicon, enabling bright single-photon emission in the telecom O-band. Deterministic electron-beam lithography and a ridge-based vertical p--i--n diode architecture enable precise device integration and electrical control of individual emitters. The QD--eCBGs exhibit a quantum-confined Stark shift of approximately 16 nm (11 meV) at 4 K, representing a record for QDs embedded in nanophotonic structures at telecom wavelengths. This is achieved alongside a photon extraction efficiency of $$(21.7 \pm 3.0)\%$$ into the first lens, while maintaining excellent radiative properties and high single-photon purity, with $$g^{(2)}(0)=0.0078 \pm 0.0012$$ below saturation and $$g^{(2)}(0)=0.0183 \pm 0.0021$$ at saturation under pulsed excitation. Robust antibunching persists up to 77 K, with $$g^{(2)}(0)=0.0663 \pm 0.0056$$, enabling operation with liquid-nitrogen or compact Stirling cryocoolers. Furthermore, spatially separated QD--eCBGs can be electrically tuned into spectral resonance without degrading photon statistics. These results establish a silicon-compatible, electrically addressable telecom O-band quantum light platform combining wide spectral tunability, high single-photon purity, and elevated-temperature operation, providing a scalable route toward practical photonic quantum networks.
A quantum dot on silicon is like an artificial atom: it confines electrons and holes in a tiny region, so it emits light of strictly defined colors.
In the series 'The Expanse', quantum communication allows instant messaging between ships, such photon sources could become the basis for real secure channels.