New quantum light source in the terahertz spectrum

A polar quantum emitter in a plasmonic cavity can convert light in the visible s
A polar quantum emitter in a plasmonic cavity can convert light in the visible spectrum into single photons in the terahertz.

A team at the Autonomous University of Madrid (UAM) has developed a tunable light source that can emit single photons in the terahertz (THz) regime. The finding opens up new frontiers in quantum technology, promising innovative applications in sectors such as spectroscopy, microscopy, medical diagnostics, communications and security.

A team from the Autonomous University of Madrid (UAM) has developed a tunable light source capable of emitting single photons in the terahertz (THz) range. This frequency regime is key to explore vibrational and rotational level transitions in molecules, as well as transitions in single and collective excitations in semiconductor materials.

The results, published in the journal PRX Quantum, open the door to unique applications in spectroscopy and microscopy, useful in areas as diverse as food science, diagnostic medicine, biology, broadband telecommunications and security.

Furthermore, this work represents the first proposal for a single photon source at THz that is compatible with the accessible parameters of today’s laboratories, marking a milestone on the road towards harnessing the unique properties of terahertz in future quantum technologies.

Quantum THz technology

Despite its potential, quantum technology in the THz range is still in its early stages, especially when compared to established technologies in the visible, near-infrared and microwave spectrums.

In the visible spectrum, quantum light has been shown to offer important technological advantages, such as metrological accuracy at the Heisenberg limit, alternative quantum computing paradigms or protection against eavesdropping in remote communications.

The application of quantum THz technology promises to extend these benefits to areas where terahertz frequencies are particularly relevant, offering an intermediate solution between the scalability limitations and extreme cooling requirements of microwaves, and the challenges of absorption and manufacturing precision in the optical spectrum.

"Specifically, our study proposes a quantum light source based on a single polar quantum emitter with a transition energy in the visible spectrum and a permanent dipole moment. By exciting the emitter with an intense optical laser, these properties allow the generation of hybrid states of light and matter with transitions allowed at THz," the authors explain.

"These transitions," they add, "give rise to the emission of single photons at THz, efficiently captured by nanoantennas. Finally, crucially, this approach offers precise control over the resulting radiation, allowing both the intensity and its quantum fluctuations to be adjusted by simply modifying the frequency and intensity of the laser excitation."

Bibliographic reference:

Groiseau, C.; Fernández-Domínguez, A.I.; Martín-Cano, D.; Sánchez Muñoz, C. (2023). Single-Photon Source Over the Terahertz Regime. PRX Quantum, 5, 010312.

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