An electrically driven light source using ensembles of indium gallium arsenide/gallium arsenide quantum dots emits circularly polarized single photons without needing external laser pumping. The device directly converts electrical charge and spin into photon emission; key fluctuations observed when detecting pairs of emitted photons disappear upon demagnetizing the layer used to inject electrons with specific spins. Electrically driven light emission was achieved using semiconductor structures called quantum dots, creating circularly polarized photons without requiring external lasers, this process directly converts electrical charge and spin into photon production.

Measurements revealed fluctuations when detecting pairs of emitted photons, a phenomenon linked to how electrons are injected with specific spins. Removing magnetism from the electron-injecting layer eliminated these fluctuations, showing that controlling electron spin influences both the polarization *and* timing characteristics of multiple photons produced by the device.

Researchers at Chinese Academy of Sciences, Université de Lorraine, and University at Buffalo SUNY developed electrically driven light sources using tiny specks of material called indium gallium arsenide/gallium arsenide quantum dots capable of emitting circularly polarized single photons without needing external lasers; these structures act like artificial atoms that emit particles of light when stimulated with electricity.

The new device directly converts electrical charge and spin into photon production, offering potential for miniaturization and efficiency gains over traditional optical methods. Removing magnetism from the electron-injecting layer eliminated these fluctuations, demonstrating that controlling electron spin influences both the polarization *and* timing characteristics of multiple photons produced by the device.

Demagnetization stabilizes two-photon emission for enhanced photonic control

Over 60% fewer fluctuations occurred in two-photon emissions when demagnetizing the device’s spin injection layer; previously, these fluctuations obscured any ability to control higher-order correlations within emitted light and limited performance metrics like indistinguishability. Directly converting electrical charge and spin into photon production became possible through electrically driven emission from InGaAs/GaAs quantum dots with controlled circular polarization, eliminating the need for external laser pumping. Measurements were taken using an extended Hanbury Brown, Twiss interferometer equipped with four detectors capable of resolving up to |2⟩ Fock states during each excitation cycle.

Despite pronounced initial fluctuations across multiple time points within electrical pulses exciting InGaAs/GaAs quantum dots, this suppression demonstrated that controlling electron spin directly impacts multi-photon behaviour. The use of a ferromagnetic CoFeB layer and MgO tunnel barrier enables efficient spin-polarized electron injection into the semiconductor region where excitons recombine; consequently, circularly polarized photon emission is possible at zero applied magnetic field. Electrical excitation offers tunability over repetition rate and pulse duration, parameters influencing exciton population dynamics and emitted light statistics, allowing exploration of how these factors affect performance beyond noise reduction.

Electrical Control Reveals Cooperative Emission Mechanisms Remain Undetermined

While electrical control over multi-photon emissions represents a clear step towards practical quantum technologies, fully understanding *how* these correlations arise remains elusive; phenomenological modelling successfully captures observed behaviour but doesn’t pinpoint specific interactions between individual light emitters within the semiconductor material itself. Optimising device performance requires knowing precisely which mechanisms govern cooperative emission effects and how to best exploit them, presenting a significant challenge due to this lack of microscopic insight.

Nevertheless, despite uncertainties around exactly how these complex interactions unfold, this achievement demonstrates electrical control over both photon colour (helicity) and timing, opening avenues for advanced light sources generating tailored streams of photons with specific properties.

Electrical means now allow manipulation of photon polarization and complex multi-photon behaviour within quantum dots, enabling precise control over their timing relationships without external lasers. A direct link became clear: injected electron spin governs simultaneous multiple light particle emissions from these tiny materials. Eliminating magnetism used in the injection process suppressed fluctuations in paired photon emissions; controlling the spin state therefore influences not just colour but also higher-order correlations crucial for future applications and laying the foundation for new sources of tailored light.

This research demonstrated that electrically injecting electrons into InGaAs/GaAs quantum dots allows control over both the color (circular polarization) and emission timing of single photons. The study found a connection between the spin of the injected electrons and fluctuations observed when measuring pairs of emitted photons, revealing electrical manipulation of multi-photon behavior. This level of control was achieved without an external laser using a device incorporating CoFeB and MgO layers to inject polarized electrons. Researchers are working to better understand the specific interactions within the material responsible for these complex emissions.

👉 More information
🗞 Probing fluctuations in photon emission statistics of spin injected quantum dots with time dependent electronic excitation
✍️ Chiran Wijesundara, Vincent Iglesias-Cardinale, Herbert Fotso and Tim Thomay (University at Buffalo SUNY); Yuan Lu (Université de Lorraine); Bo Xu (Chinese Academy of Sciences)
🧠 ArXiv: https://arxiv.org/abs/2610.40593

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