Atoms Linked to Light Pave Way for Faster, Scalable Computers

Scientists have long sought to integrate the strengths of neutral-atom arrays with optical cavity interfaces to create scalable quantum computing architectures.

Jacopo De Santis, Balázs Dura-Kovács, and Mehmet Öncü, all from the Max-Planck-Institut für Quantenoptik, alongside Adrien Bouscal from the same institution and working with colleagues at Technische Universität München, including Dimitrios Vasileiadis, and Johannes Zeiher from the Max-Planck-Institut für Quantenoptik, now report the realisation of a cavity-coupled Rydberg array that addresses this critical challenge. This novel platform successfully combines high-fidelity Rydberg state control within a scalable optical tweezer array with strong coupling to a high-finesse optical cavity, demonstrated through dispersive shifts and enhanced Rydberg interactions at the same spatial location. The resulting experimental setup promises to unlock new avenues in quantum information science, potentially enabling the development of quantum nodes, simulations of complex systems, and advanced photonic state engineering. This long-sought combination represents a crucial step towards building a practical quantum internet and enabling distributed quantum computing. The research details the creation of a novel cavity-coupled Rydberg array, overcoming substantial experimental challenges to integrate these capabilities at the same spatial location. This innovative platform allows for the preparation, detection, and precise control of individual atoms within a scalable optical tweezer array, coupled strongly to the optical mode of a high-finesse cavity and excited to Rydberg states in a controlled manner. A high-finesse optical cavity and an optical tweezer array form the core of this experimental work, enabling precise manipulation and observation of individual atoms. Atoms were initially trapped using the optical tweezer array, a technique employing tightly focused laser beams to hold and position neutral atoms in three dimensions. This array configuration allows for scalable arrangements of atoms, crucial for building complex quantum systems, and the chosen tweezer wavelength facilitated both atom trapping and subsequent Rydberg excitation, streamlining the experimental sequence. Following atom trapping, the array was positioned within the mode of a high-finesse optical cavity, a resonant structure designed to enhance the interaction between light and matter. This cavity, constructed with highly reflective mirrors, amplified the coupling between the atoms and photons, a key requirement for strong-coupling cavity quantum electrodynamics. An electric-field shielding platform was integrated to minimise external disturbances and maintain the integrity of the Rydberg states. Individual atoms within the array were then prepared and detected using a combination of laser spectroscopy and high-resolution imaging. High-fidelity (99.988%) and high-survival (99.88%) imaging was achieved using bimodal count histograms, allowing for precise identification of atom positions and states. A Raman transition was employed to transfer atoms into a specific ground state, |g⟩= |5S1/2, F = 1, mF = −1⟩, before excitation to the Rydberg state |r⟩= |53S1/2⟩, ensuring optimal control over the atomic interactions and their coupling to the cavity. Rydbium excitation was achieved using counter-propagating laser beams at 1015nm and 420nm, driving the atoms to highly excited Rydberg states, facilitating efficient excitation while minimising off-resonant transitions. The work demonstrates strong coupling between the atom arrays and the optical cavity, evidenced by a dispersive shift in the cavity’s resonance when atoms are present. Simultaneously, strong Rydberg interactions are observed through the collective enhancement of Rydberg coupling within the atomic array. Initial experiments reveal a free-spectral range of 7.79GHz for the high-finesse optical cavity, a value consistent with calculations based on the 20mm mirror separation. Scanning a probe beam across the expected cavity resonance unexpectedly revealed a splitting into several modes, separated by approximately 3MHz, each exhibiting a linewidth of 2π × 0.84MHz. This spectral structure is attributed to hybridization of low-order modes within the cavity system. Fitting a sum of Lorentzian peaks to the cavity transmission signal, researchers determined the cavity cooperativity, a crucial metric for quantifying light-matter interaction strength, to be C = 4g²/κΓ. Measurements of Rydberg resonance shifts as a function of applied voltage confirm effective electric field shielding, crucial for maintaining atomic coherence. The platform sustains continuous cooling of atoms within optical tweezers for 322 seconds, despite the proximity of cavity mirror assemblies, demonstrating long vacuum-limited lifetimes and stable operation. Initial loading probabilities reached 52.0 percent, with Raman sideband cooling achieving an average motional occupation of n = 0.62 in one dimension, indicating precise control over atomic motion. This dual achievement signifies a major advancement in the field of quantum information science, paving the way for new avenues of research and technological development. The presented experimental platform opens possibilities for realising quantum network nodes, simulating complex quantum systems, and engineering advanced photonic states with high-fidelity Rydberg control. Researchers anticipate exploring the realization of quantum network nodes, which would serve as building blocks for a future quantum internet. Furthermore, the platform is well-suited for simulating long-range interacting quantum systems, offering insights into complex physical processes, and the high-fidelity Rydberg control enables the engineering of advanced photonic states, potentially leading to new applications in quantum communication and sensing. For years, researchers have struggled to integrate the strengths of different quantum platforms, the processing power of atom arrays and the communication capabilities of photons, into a single, cohesive system. The ability to strongly couple these elements, particularly while leveraging the enhanced interactions offered by Rydberg states, has remained elusive. This advance isn’t merely about demonstrating a technical capability; it’s about unlocking a pathway to a truly distributed quantum internet, facilitating the efficient distribution of quantum information over considerable distances, a necessity for linking quantum processors and creating a network capable of tackling problems beyond the reach of even the most powerful classical computers. The platform also promises exciting possibilities for simulating complex physical systems and engineering novel photonic states with unprecedented control. However, translating this laboratory success into practical devices isn’t straightforward, as maintaining the delicate coherence of these quantum states, particularly in the face of environmental noise, remains a formidable hurdle. While the experiment demonstrates strong coupling, quantifying the precise degree of that coupling and its stability over extended periods is vital for future development. Looking ahead, the focus will likely shift towards scaling up the number of atoms in the array and integrating multiple such modules, creating a modular quantum computer architecture, with broader efforts undoubtedly exploring different atom species and cavity designs, all aimed at enhancing performance and robustness. 👉 More information 🗞 Realization of a cavity-coupled Rydberg array 🧠 ArXiv: https://arxiv.org/abs/2602.12152 Tags: