Long-lived giant circular Rydberg atoms at room temperature

TL;DR

The work tackles the finite lifetimes of typical Rydberg states that limit gate fidelity and coherence in neutral-atom quantum platforms. It introduces a microwave-capacitance suppression capacitor to engineer Purcell suppression of blackbody radiation at room temperature and demonstrates coherent control of circular Rydberg states up to $n=103$, with lifetimes surpassing $10\,\mathrm{ms}$. Notably, the authors achieve a measured $\tau(\ket{101\mathrm{C}})=11.5(8)\,\mathrm{ms}$ and trap CRS in optical tweezers with a $1/e$ lifetime of $133(6)\,\mathrm{ms}$, enabling significantly longer quantum evolution and stronger Rydberg blockade. This advances the feasibility of long-duration, high-fidelity quantum simulation and sensing using CRS in room-temperature setups, and points toward scalable, dissipationless protocols leveraging extreme lifetimes and strong blockade.

Abstract

Stability achieved by large angular momentum is ubiquitous in nature, with examples ranging from classical mechanics, over optics and chemistry, to nuclear physics. In atoms, angular momentum can protect excited electronic orbitals from decay due to selection rules. This manifests spectacularly in highly excited Rydberg states. Low angular momentum Rydberg states are at the heart of recent breakthroughs in quantum computing, simulation and sensing with neutral atoms. For these applications the lifetime of the Rydberg levels sets fundamental limits for gate fidelities, coherence times, or spectroscopic precision. The quest for longer Rydberg state lifetimes has motivated the generation, coherent control and trapping of circular Rydberg atoms, which are characterized by the maximally allowed electron orbital momentum and were key to Nobel prize-winning experiments with single atoms and photons. Here, we report the observation of individually trapped circular Rydberg atoms with lifetimes of more than 10 milliseconds, two orders of magnitude longer-lived than the established low angular momentum orbitals. This is achieved via Purcell suppression of blackbody modes at room temperature. We coherently control individual circular Rydberg levels at so far elusive principal quantum numbers of up to $n=103$, and observe tweezer trapping of the Rydberg atoms on the few hundred millisecond scale. Our results pave the way for quantum information processing and sensing utilizing the combination of extreme lifetimes and giant Rydberg blockade.

Figures (9)

• Figure 1: Suppression capacitor and coherent high-$n$ circular state control. (a) Experimental setup: A circular Rydberg atom is trapped in an optical tweezer at the center of an electrode structure. This structure consists of four ring-shaped electrodes in the $xy$-plane in between two indium tin oxide (ITO)-coated glass plates, the latter forming the BBR suppression capacitor. Applied electric and magnetic fields along $z$ (quantization axis) orient the circular Rydberg orbit so that it lies in the $xy$-plane. (b) Sketch of the succession of Landau-Zener MW pulses ($\mathrm{LZ}_i$) and the electric field sequence ($E_z$) applied for preparing CRS up to $n=103$ starting from $\ket{79\mathrm{C}}$. Each pulse $\mathrm{LZ}_i$ drives a two-photon transition in the simplified level scheme depicted in (c), while $E_z$ is ramped linearly across the resonance condition for coherent Landau-Zener population transfer. After a hold time $t_\mathrm{h}$ at a fixed field $E_\mathrm{h}$, the final Rydberg state is detected via state-selective field ionization (SSFI) by applying a large field $E_x$ ramp. (d) SSFI measurements of Landau-Zener sweeps of four exemplary transitions up to $n=87$, showing adiabatic transfer ($\ket{n\mathrm{C}} \leftrightarrow \ket{n+2\mathrm{C}}$) when the $\mathrm{LZ}_i$ pulse duration is sufficiently long.
• Figure 2: Circular state microwave spectra. (a) Measured microwave resonance frequencies for two-photon transitions as a function of the applied electric field along $z$, with principal quantum number ranging from $n=79$ to $n=103$. Circles (triangles) show data for transitions from $\ket{n\mathrm{C}}$ to circular (elliptical) states with $n+2$. Solid lines show the prediction from a hydrogen model for $\sigma^+\sigma^+$ transitions between CRS (blue), and the nearby $\pi\pi$ transitions connecting a CRS to an elliptical state (red) as indicated in the level scheme shown in (e). The zoom-ins (b)--(d) demonstrate the spectroscopic resolution between both second-order Stark shifted transitions in the electric field, which allows us to selectively address $\sigma^+\sigma^+$ transitions for high-$n$ CRS preparation. Errorbars show the FWHM of the measured resonance signals.
• Figure 3: Circular Rydberg state lifetimes. (a, b) SSFI histograms of the arrival time distribution on the MCP as a function of the hold time $t_\mathrm{h}$, for atoms initially prepared in $\ket{89\mathrm{C}}$ (a) and $\ket{97\mathrm{C}}$ (b). Vertical gray lines indicate the bins used to distinguish Rydberg manifolds with principal quantum numbers $n$ as indicated on top. The top row shows the histogram integrated over $t_\mathrm{h}$. (c), (d) Relative state populations in the different $n$-manifolds (symbols with $n$ as indicated) evaluated from the histograms in (a) and (b), respectively. For better visibility only five $n$-values around the initial state are depicted. Solid lines show a rate model fit to the data, from which the lifetime of the initial CRS is extracted. The data in (a) and (b) is obtained from 4,000 realizations of the experiment for each value of $t_\mathrm{h}$. (e) Measured CRS lifetime (red circles) as a function of $n$, obtained from data sets as shown in (c), (d) for different initial states $\ket{n\mathrm{C}}$ (data point for $n=77$ from Hoelzl2024). The top abscissa indicates the corresponding criteria $2d/\lambda$ for $\sigma^+$ blackbody suppression, with $\lambda$ the microwave transition wavelength to $\ket{n+1\mathrm{C}}$. Calculated lifetimes in free space (green), in an infinitely extended capacitor with finite reflectivity (gray), and in our full simulated electrode structure (blue) at a temperature of 300K are shown for comparison. Shaded areas of the capacitor calculations account for uncertainties in the ITO plate distance and reflectivity (see text). Errorbars in (c), (d) and (e) depict $1\sigma$-confidence intervals.
• Figure 4: Rydberg atom tweezer lifetime. Measured loss of all detected Rydberg states (total ion signal on the MCP) as a function of the hold time $t_\mathrm{h}$ for initial preparation of $\ket{97\mathrm{C}}$ with the tweezer kept on (blue circles) and switched off (red circles). Ion counts are normalized to the initial value. The solid line is an exponential fit to the data to extract the 1/e trapping lifetime. Turning the tweezer off at $t_\mathrm{h}=0$ results in rapid loss of the signal within a millisecond (see inset), because the Rydberg atoms leave the trapping region and are no longer detected by our SSFI protocol. Errorbars indicate one standard error of the mean.
• Figure 5: Single-photon lightshifts. Measured resonances of two-photon transitions from $\ket{85\mathrm{C}}$ to $n=87$ compared to the transition $\sigma^+\sigma^+$ resonance between CRS (blue), and the nearby $\pi\pi$ transition to an elliptical state (red), following the same procedure as in Fig. \ref{['fig:Fig2']}. Different shades and markers indicate different power settings of the MW source. The data points are lightshifted away from the $\pi\pi$ resonance (red line) by a single-photon $\pi$ transition, connecting the excited state to $n=88$ (red dashed line). Errorbars denote the FWHM of the measured resonances.