Work

Detection of photon-level signals embedded in sunlight with an atomic photodetector

Year: 2026

Type: article

Abstract: The detection of few-photon signals in a broadband background is an extreme challenge for photon counting, requiring filtering that accepts a narrow range of optical frequencies while strongly rejecting all others. Recent work [Zarraoa et al., Phys. Rev. Res. 6, 033338 (2024)] demonstrated that trapped single atoms can act as low dark-count narrow-band photodetectors. Here, we show that this “quantum jump photodetector” (QJPD) approach can also detect photon-level signals embedded in strong sunlight. Using a single rubidium atom as a QJPD, we count arrivals of individual narrow-band laser photons embedded in sunlight powers of order 1010 photons/s. We derive a rate-equation model for the atom's internal-state dynamics in sunlight and find quantitative agreement with experiment. Using this model, we calculate the channel capacity over a noisy communication channel when sending weak coherent states and detecting them in the presence of sunlight, achieving a representative rate of 0.5 bits/symbol when sending 150 probe photons per 10 ms time bin, embedded in 1 nW of sunlight (of order 1010 photons/s in the visible and near-infrared bands). The demonstration may benefit background-limited applications such as daytime light detection and ranging, remote magnetometry, and free-space classical and quantum optical communications.

Source: AVS Quantum Science

DOI: 10.1116/5.0314886

Authors: Laura Zarraoa, Tomas Lamich, Sondos Elsehimy, Morgan W. Mitchell, Romain Veyron

Institutions: Institute of Photonic Sciences, Barcelona Institute of Science and Technology, Institució Catalana de Recerca i Estudis Avançats

Language: English

Topic: Quantum optics and atomic interactions

Subfield: Atomic and Molecular Physics, and Optics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green