Fast Single-Shot Imaging of Individual Ions via Homodyne Detection of Rydberg-Blockade-Induced Absorption

Jinjin Du, Thibault Vogt, and Wenhui Li

Phys. Rev. Lett. 130, 143004 – Published 6 April 2023

Abstract

We introduce well-separated ${}^{87}{Rb}^{+}$ ions into an atomic ensemble by microwave ionization of Rydberg excitations and realize single-shot imaging of the individual ions with an exposure time of $1 μ s$ . This imaging sensitivity is reached by using homodyne detection of ion-Rydberg-atom interaction induced absorption. We obtain an ion detection fidelity of ( $80 \pm 5$ )% from analyzing the absorption spots in acquired single-shot images. These in situ images provide a direct visualization of the ion-Rydberg interaction blockade and reveal clear spatial correlations between Rydberg excitations. The capability of imaging individual ions in a single shot is of interest for investigating collisional dynamics in hybrid ion-atom systems and for exploring ions as a probe for measurements of quantum gases.

Received 18 September 2022
Accepted 7 March 2023

DOI:https://doi.org/10.1103/PhysRevLett.130.143004

Physics Subject Headings (PhySH)

Electric dipole-dipole interactions Electromagnetically induced transparency Long-range interactions Rydberg gases

Atoms Ions Rydberg atoms & molecules

Imaging & optical processing

Atomic, Molecular & Optical

Authors & Affiliations

Jinjin Du ¹, Thibault Vogt ^1,2,*, and Wenhui Li ^1,3,†

¹Centre for Quantum Technologies, National University of Singapore, 3 Science Drive 2, Singapore 117543
²School of Physics and Astronomy, Sun Yat-sen University, Zhuhai 519082, China
³Department of Physics, National University of Singapore, 117542, Singapore

^*ttvogt@mail.sysu.edu.cn
^†wenhui.li@nus.edu.sg

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Vol. 130, Iss. 14 — 7 April 2023

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Images

Figure 1
(a) Energy level schemes for ion production and multiphoton EIT detection. (b) Sketch of the experimental setup. The 780 nm excitation beam reaches the atomic cloud after passing through a slit and a telescope (not shown), which limits the excitation to a segment of the atomic cloud $V_{I}$ bounded by the two dashed lines. The 780-nm beam propagating along the + $z$ direction is a superposition of the $σ^{+}$ probe field and the $σ^{-}$ reference field. After the analyzer [a half wave-plate (HWP) and a polarizing beam splitter (PBS)], the interference image is collected by an electron-multiplying charge-coupled-device (EMCCD) camera. A bias magnetic field is applied vertically to define the quantization axis. (c) Enlarged view at the volume $V_{I}$ exposed to excitation and ionization, with a cartoon illustration of two Rydberg superatoms (two closely packed transparent balls), ground-state atoms (black dots), and two ion-Rydberg interaction blockades (orange balls), which cast two absorption spots due to the ions on the camera screen (black spots). Here $R_{b}$ and $R_{b − ex}$ are defined in the text, and the dashed lines in (b) and (c) delimit the same area. Note that microwave ionization can occur anywhere within a Rydberg superatom, therefore the resulting ion is not necessarily at the center of the Rydberg superatom.
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Figure 2
Gaussian smoothed (filter $size = 2 pixels$ ) single-shot images. (a), (b) Absorption spots of one ion and two ions present in $A_{I}$ , respectively. (c) No ion present in $A_{NoI}$ . (d) Absorption spots of two ions from simulation. The dashed rectangles in (b) and (c) [that in (a) is not drawn] respectively indicate $A_{I}$ and $A_{NoI}$ , where the horizontal dashed lines, separated by $4 σ_{r}$ , correspond to the $1 / e^{2}$ radius of the atomic cloud and the vertical ones are separated by $a_{x}$ .
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Figure 3
Histograms of the peak absorption amplitudes of the two largest peaks (a) and of all the peaks (b) inside the area $A_{I}$ (red) vs histogram of all the local “absorption” maxima inside $A_{NoI}$ (blue). The solid-line profiles are the results of theoretical simulations carried out using the experimental parameters. The vertical dashed lines indicate the threshold $A_{thld} = 6 %$ . The distributions are from the statistics of about 500 single-shot images.
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Figure 4
(a) and (b) Histograms of the radii $σ_{x}$ and $σ_{y}$ extracted from fitting a two-dimensional Gaussian distribution to the absorption spots of peak amplitude larger than $A_{thld}$ . The solid lines are the results from theoretical simulations. The distributions are from the statistics of nearly 400 single-shot images, each of which contains up to two absorption spots of peak amplitude larger than $A_{thld}$ .
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Figure 5
(a) Two-dimensional (2D) distribution of the peak positions of two ions in a single-shot image. The dashed rectangle corresponds to the area $A_{I}$ . The thin lines are the result of a 2D Gaussian contour fit. (b) Pair correlation function of the positions of two ions in single-shot images. The error bars represent the standard error over more than 200 images. For this figure, we choose the single-shot images having the two absorption spots of peak amplitude larger than $A_{thld}$ .
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