# The 27th International Conference on Atomic Physics

17-22 July 2022
Royal Conservatory of Music, Toronto
America/Toronto timezone

## A single cold atom as a single-photon detector.

19 Jul 2022, 17:00
1h 30m
Hart House (Hart House)

### Hart House

#### Hart House

7 Hart House Cir, Toronto, ON M5S 3H3
Poster presentation Quantum optics and hybrid quantum systems

### Description

Single ions and atoms are interesting systems for single-photon detection due to their frequency selectivity and very low dark counts [2,3]. These capabilities are useful for any application in which a very low power signal must be detected against a broadband background. An example of such an application would be free-space quantum communication in daylight.
In this work, we present and describe the operation of a quantum jump photodetection (QJPD) technique for measuring single photons using a single neutral 87Rb atom in a strongly-focused optical dipole trap [4,5]. We report results of first-principles calculations for the main dark count contributions: spontaneous Raman transitions driven by readout light (which can be avoided by separating the detection and readout time windows) and spontaneous Raman transitions driven by trap light (which is unavoidable but gives dark count rates two orders of magnitude below that state of the art single-photon detectors). We quantify the frequency selectivity with the \textit{equivalent noise bandwidth}, which we find is up to two orders of magnitude narrower than the best atomic filters. Preliminary experimental results for these figures of merit in a Maltese cross'' atom trap will be presented.

1[Quantum-Jump Photodetection technique for a single neutral 87Rb atom in a free-space dipole trap. a) Relevant energy levels and lights used in the experiment. Cooler light (orange) for preparation and readout in the closed transition and signal light (purple) that will be measured. b) Measurement sequence. First cooler pulse prepares atom in the dark ground state (F=1), signal pulse causes a quantum jump to the bright state (F=2), readout pulse causes sudden fluorescence if the atom jumped and then reprepares the atom in the dark state. c) Counts as a function of time for a detection event. The sudden increase in fluorescence counts due to the atom cycling in the closed transition after a jump creates a well-above background peak that can be used for counting detections.][2]

[2] C. Kurz, et al., Phys. Rev. A 93, 062348 (2016)
[3] N. Piro, et al. Nature Phys 7, 17–20 (2011)
[4] N. Bruno, et al., Opt. Express 27, 31042-31052 (2019).
[5] L. Bianchet, et al., Open Res Europe, 1:102 (2021).

Presenter name Laura Zarraoa

### Primary authors

Laura Zarraoa (ICFO - Institute of Photonic Sciences) Prof. Morgan Mitchell (ICFO)

### Presentation Materials

There are no materials yet.