arXiv subjects

Laura Zarraoa

Publications and source records attributed to Laura Zarraoa.

5 recordsLinked to original sources

arXiv2026

A single atom emitting resonance fluorescence into a coherent beam, and its use for non-destructive atom thermometry

Using a far-off-resonance optical dipole trap, we place a single neutral $^{87}$Rb atom in a weak, atom-resonant coherent beam, while also strongly illuminating it from an orthogonal direction to produce resonance fluorescence. The atom-modified coherent beam is then collected and its photon statistics analyzed. We observe first-order interference that can increase or decrease the beam flux, depending on the relative phase of the coherent beam and resonance fluorescence. This confirms predictions of Goncalves et al. [Phys. Rev. A 104, 013724]. The interference visibility is also shown to be a sensitive, time-resolved, non-destructive thermometer: by fitting the resulting photon count distributions, we infer the center-of-mass localization of the atom within the trap. With $1200$ atoms and integration time of $80\mathrm{ms}$ per atom, we demonstrate temperature uncertainties of $4 %$ for $\sim 30 \mu\mathrm{K}$ temperatures at $\sim 200\mu\mathrm{s}$ time resolution.

physics.atom-ph↗

arXiv2025

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

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 $10^{10}$ 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 per symbol when sending 150 probe photons per 10 ms time-bin, embedded in 1 nW of sunlight (of order $10^{10}$ photons/s in the visible and near-infrared bands). The demonstration may benefit background-limited applications such as daytime light detection and ranging (LIDAR), remote magnetometry, and free-space classical and quantum optical communications.

quant-ph↗

arXiv2024

Precise, super-resolving intensity measurement by quantum jump spectroscopy of a single neutral atom

We present precise, sub-wavelength optical intensity measurement using a single trapped $^{87}$Rb atom as a sensor. The intensity is measured by the scalar ac Stark shift it produces on the $F=1 \rightarrow F'=2$ hyperfine transition of the D$_{2}$ line, chosen for its $F' = F+1$ structure and very small tensor polarizability. To boost signal and reduce measurement-induced perturbations, we use a quantum jump spectroscopy technique in which a single absorbed photon on a transition of interest induces the scattering of hundreds of photons on a bright closed transition. The method greatly reduces systematic effects associated with the atomic state, optical polarization, probe power, and atom heating, and gives the atomic temperature as a second spectroscopic observable. We demonstrate the method by measuring the intensity at the focus of an optical tweezer.

physics.atom-ph↗

arXiv2024

Quantum jump photodetector for narrowband photon counting with a single atom

Using a single neutral 87Rb atom held in an optical trap, and "quantum jump" detection of single-photon-initiated state changes, we demonstrate a single-photon quantum jump photodetector (QJPD) with intrinsically narrow bandwidth and strong rejection of out-of-band photons, of interest for detecting weak optical signals in the presence of a strong broadband background. By analyzing fluorescence photon count distributions for the bright and dark states with and without excitation, we measure quantum efficiency of 2.9(2)$\times 10^{-3}$, a record for single-pass quantum jump production, and signal-photon-unprovoked "dark jump" rate - analogous to the dark count rate of other detectors - 3(10)$\times 10^{-3}$ jumps per second during passive accumulation plus 4.0(4)$\times 10^{-3}$ jumps per readout, orders of magnitude below those of traditional single-photon detectors. Available methods can substantially improve QJPD quantum efficiency, dark jump rate, bandwidth and tunability.

quant-ph↗

arXiv2021

Manipulating and measuring single atoms in the Maltese cross geometry

We describe optical methods for trapping, cooling, and observing single $^{87}$Rb atoms in a four-lens "Maltese cross" geometry (MCG). The use of four high numerical-aperture lenses in the cardinal directions enables efficient collection of light from non-collinear directions, but also restricts the optical access for cooling and optical pumping tasks. We demonstrate three-dimensional atom localization with sub-wavelength precision, and present measurements of the trap lifetime, temperature and transverse trap frequency in this geometry. We observe a trap performance comparable to what has been reported for single-atom traps with one- or two-lens optical systems, and conclude that the additional coupling directions provided by the MCG come at little cost to other trap characteristics.

physics.atom-ph↗