Light at the Flick of a Switch: How an Infrared Beam Boosts Quantum Sources express
A glowing spot on a crystal is like a firefly that you can wake not only with a flashlight but also with the warmth of your palm. Such spots, single-photon sources, can emit light one particle at a time, which is essential for quantum communication and computing. Usually, they are 'woken up' with visible light, but the details of this awakening have long remained murky.
Now, a second beam has been added to the visible one — invisible, mid-infrared, with a wavelength of about 7.3 micrometers. This beam resonates with atomic vibrations around the defect in hexagonal boron nitride — a material similar to graphite but transparent. The vibrations, like a swing, rock back and forth and help charge carriers recombine faster: that is, come together and emit a photon. As a result, the blue light sources shine brighter.
Such a 'gas pedal' for quantum emitters has never been used before. The method works at room temperature, without complex cryostats. It is a step toward practical devices: single-photon sources could be tuned on the fly, like the volume on a radio.
Original abstract
as written by the authors arXiv:2603.08466
Single photon emitters (SPEs) are promising building blocks for practical devices in quantum technologies. Traditionally, these systems are excited using off-resonant visible light through their phonon transitions, yet this process remains poorly understood. Here, we explore the interaction of mid-infrared (MIR) excitation on the properties of SPEs in hexagonal boron nitride. Notably, we present a reversible, non-destructive method to enhance emission from blue SPEs using MIR co-excitation. By resonantly driving defect-localized in-plane infrared-active optical phonon modes near 7.3 um, the MIR field modulates carrier dynamics through a phonon-assisted recombination. This unique feature, not observed previously for defects in solids, is a promising reservoir in a growing toolkit to modulate quantum emitters at room temperature for their use in practical quantum technologies.
A wavelength of 7.3 micrometers is about ten times thinner than a human hair, and such light is invisible to the eye but perfectly 'heard' by crystal lattice vibrations.