Deterministic single-photon source over the terahertz regime

arXiv:2509.26486v2 Announce Type: replace Abstract: The terahertz (THz) regime still lacks a source capable of emitting single photons deterministically. Here, we propose an on-demand THz single-photon source, triggered by a sequence of coherent optical pulses used to dress a polar quantum emitter. The permanent dipole moment of the emitter activates THz transitions within its Rabi-split doublets, which are enhanced through resonant coupling to a THz cavity. We identify a challenge unique to this platform: spontaneous emission of visible photons competes with the THz process, degrading performance in two distinct ways depending on the sign of the drive detuning---either increasing the vacuum component, reducing brightness, or increasing multiphoton contributions, reducing purity. We demonstrate how to overcome those challenges through optimized pulse areas and a sufficiently high Purcell rate. A hybrid resonator-nanoparticle design for a cavity satisfying the latter requirement is presented, yielding efficiencies of 65-92\% and purities of 88-100\%, comparable to the best visible single-photon sources, while providing broad tunability across the THz range. Finally, we exploit the visible emission itself, using its detection to fully reconstruct the THz photon-number distribution and herald a single THz photon, boosting efficiency to 90-95\%. All these capabilities illustrate the new technological opportunities unlocked by the unique integration of terahertz and visible frequencies.

Abstract:The terahertz (THz) regime still lacks a source capable of emitting single photons deterministically. Here, we propose an on-demand THz single-photon source, triggered by a sequence of coherent optical pulses used to dress a polar quantum emitter. The permanent dipole moment of the emitter activates THz transitions within its Rabi-split doublets, which are enhanced through resonant coupling to a THz cavity. We identify a challenge unique to this platform: spontaneous emission of visible photons competes with the THz process, degrading performance in two distinct ways depending on the sign of the drive detuning---either increasing the vacuum component, reducing brightness, or increasing multiphoton contributions, reducing purity. We demonstrate how to overcome those challenges through optimized pulse areas and a sufficiently high Purcell rate. A hybrid resonator-nanoparticle design for a cavity satisfying the latter requirement is presented, yielding efficiencies of 65-92\% and purities of 88-100\%, comparable to the best visible single-photon sources, while providing broad tunability across the THz range. Finally, we exploit the visible emission itself, using its detection to fully reconstruct the THz photon-number distribution and herald a single THz photon, boosting efficiency to 90-95\%. All these capabilities illustrate the new technological opportunities unlocked by the unique integration of terahertz and visible frequencies.

Quantum Physics (quant-ph); Mesoscale and Nanoscale Physics (cond-mat.mes-hall); Optics (physics.optics)

arXiv:2509.26486 [quant-ph]

(or arXiv:2509.26486v2 [quant-ph] for this version)

https://doi.org/10.48550/arXiv.2509.26486 Focus to learn more arXiv-issued DOI via DataCite

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Deterministic single-photon source over the terahertz regime

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