2025/09/30 by Caspar Groiseau, Miguel Á. Martínez-García, Groiseau, Caspar +5
Physics and Astronomy · #cond-mat.mes-hall #physics.optics #quant-ph
paper · pdf · doi:10.48550/arxiv.2509.26486
22 pages, 11 figures
arxiv created 2026/07/29 · arxiv updated 2026/07/30
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.