Bright quantum light emitted from a single zinc selenide impurity

Researchers at the University of Maryland and Forschungszentrum Jülich have demonstrated coherent quantum light emission from a single impurity-bound exciton in zinc selenide. The work reports a Debye-Waller factor of 0.94, indicating a high efficiency in emitting to the zero-phonon line and suggesting the material’s potential for maintaining quantum coherence.

Time-resolved measurements further revealed a slow spontaneous ionization process with a lifetime of 21 microseconds, differing from faster optically driven ionization, and enabling unique control over the emitter. These results allow for the generation of quantum light and exploration of low-photon-number nonlinear optics through resonant excitation of impurity-bound excitons.

Resonant Driving Enables Coherent Emission from ZnSe Impurity-Bound Excitons

A Debye-Waller factor of 0.94 indicates a level of control essential for applications demanding precise manipulation of quantum states. The team’s work revealed a distinct temporal dynamic governing the behavior of impurity-bound excitons within the ZnSe; time-resolved measurements showed a fast ionization process driven by optical excitation alongside a slower, 21-microsecond spontaneous ionization process stemming from charge tunneling from the impurity. This comparatively slow decay, facilitated by charge tunneling, provides a unique window for observation and control, contrasting with the more immediate effects of optical driving and enabling detailed study of the exciton’s quantum properties.

The ability to differentiate these ionization pathways is crucial for refining models of impurity behavior in semiconductors. Resonant driving of a single impurity-bound exciton enabled the observation of an intensity-dependent nonlinear phase shift at low photon numbers, a key advancement for building low-photon-number nonlinear optics.

This phenomenon, observed at the single-photon level, signifies a step toward manipulating light with increased precision. The study reports that “resonant excitation enables direct measurement of the Debye-Waller factor,” highlighting the technique’s utility in characterizing material properties relevant to quantum light emission. The research involved collaboration between scientists at the University of Maryland, including Yuxi Jiang, Robert M. Pettit, Jasvith Raj Basani, and Amirehsan Alizadehherfati, alongside Christine Falter, Nils von den Driesch, and Yurii Kutovyi from Forschungszentrum Jülich.

Alexander Pawlis and Edo Waks also contributed to the findings, which were published in npj Quantum Information.