Spin-Phonon Coupling in Rydberg Atom Arrays Drives New Symmetry-Breaking Phase

Rydberg atom arrays represent a powerful and increasingly precise platform for investigating the complex behaviour of many-body physics, but traditional models often treat atoms as static entities. Shuo Zhang, Langxuan Chen, and Pengfei Zhang, all from Fudan University, now demonstrate that incorporating atomic vibrations fundamentally alters this picture. Their research reveals that allowing atoms to vibrate introduces new interactions between them, leading to the emergence of previously unseen phases of matter and suppressing the breakdown of predictable thermal behaviour in certain quantum states. This work is significant because it bridges the gap between simplified theoretical models and the reality of experimental systems, offering a pathway to explore more complex quantum phenomena and potentially unlock new avenues for quantum technologies

Exceptional precision and controllability characterise current experiments with ultracold atoms. Traditionally, each atom is modelled as a quantum degree of freedom, simplifying analysis and enabling the discovery of novel equilibrium and non-equilibrium phases. In this work, researchers investigate the consequences of incorporating atomic vibrations in optical tweezers, which introduces a coupling between the atoms’ internal quantum states and their physical motion.

Rydberg Atoms Enable Tunable Quantum Interactions

Rydberg atoms, excited to very high energy levels, are exceptionally sensitive to electric fields, enabling strong, long-range interactions crucial for building quantum technologies. This sensitivity allows for precise control and manipulation of individual atoms, and the interaction strength can be tuned by adjusting the excitation wavelength and atomic species, providing a versatile platform for quantum simulation and computing. These atoms also exhibit long coherence times and can be individually addressed and controlled within arrays. Researchers commonly trap and manipulate Rydberg atoms using optical tweezers, highly focused laser beams that hold the atoms in place.

Optical lattices create ordered arrays, while ponderomotive bottle traps confine individual atoms in three dimensions. Specific wavelengths of light can create “magic wavelengths” where atoms are insensitive to laser fluctuations, further enhancing coherence. Rydberg atom platforms are explored for quantum simulation, mimicking complex quantum systems to study phenomena difficult to investigate directly, including many-body physics, spin models, and topological phases of matter. Researchers also investigate Kibble-Zurek scaling and simulate polaron behavior relevant to biophysics. In quantum computing, Rydberg atoms serve as qubits, and their strong interactions implement quantum gates.

Researchers work on implementing quantum error correction schemes and building robust logical qubits. Specific systems being simulated include antiferromagnets, spin liquids, kinetically constrained systems, molecular dynamics, and the Jahn-Teller effect. A significant area of research focuses on quantum many-body scars, special states defying typical thermalisation. Researchers are also developing mid-circuit correction techniques and improving entanglement and detection of alkaline-earth Rydberg atoms. Efforts are underway to scale up these systems, build hybrid approaches combining Rydberg atoms with other quantum technologies, and develop open-source software tools for calculating atomic properties.

Investigations into driven systems and the interaction between atoms and phonons are also ongoing. Rydberg atom experiments have demonstrated systems with over 256 qubits, and significant progress has been made in achieving high-fidelity quantum gates. Simple quantum algorithms have been implemented, and the field is rapidly evolving with new breakthroughs reported regularly. This combination of strong interactions, individual addressing, and increasing qubit numbers makes Rydberg atom quantum simulation and computing a particularly exciting area of research.

Vibrational Interactions Reveal New Quantum Phase

Researchers have uncovered a new quantum phase and demonstrated its influence on complex quantum systems using arrays of Rydberg atoms. These atoms, held in place by optical tweezers, serve as a highly controllable platform for exploring fundamental physics. This work expands upon traditional models by incorporating the atoms’ natural vibrations, revealing that these vibrations significantly alter the system’s properties and introduce novel interactions. The team discovered a previously unknown symmetry-breaking phase, a distinct state of matter arising from the interplay between the atoms’ internal quantum states and their physical motion.

This new phase emerges due to effective three-spin interactions mediated by the atomic vibrations, demonstrating that considering the full motional degrees of freedom is crucial for understanding the system’s behavior. The discovery expands the known landscape of quantum phases beyond those predicted by simpler models. Furthermore, the research demonstrates that incorporating these vibrations suppresses the unusual persistence of quantum states in a specific ordered arrangement. Typically, certain initial conditions lead to states that resist the natural tendency towards thermal equilibrium, exhibiting prolonged oscillations.

However, the introduction of atomic vibrations provides additional pathways for energy dissipation, effectively damping these oscillations and promoting a return to thermal behavior. This suppression of “quantum scars” offers insights into the dynamics of complex quantum systems and their eventual approach to equilibrium. The findings are particularly significant because they demonstrate the importance of considering atomic motion in Rydberg atom array experiments. By accurately modeling the coupling between the atoms’ internal and external degrees of freedom, researchers can gain a more complete understanding of quantum many-body systems and potentially harness their unique properties for future quantum technologies. The results provide experimentally verifiable predictions and pave the way for exploring even more complex quantum phenomena in these highly controllable platforms.

Atomic Motion Drives Symmetry Breaking and Thermalisation

This research investigates the impact of atomic motion on the behavior of Rydberg atom arrays, a promising platform for exploring quantum physics. Traditionally, these arrays are modeled assuming the atoms remain stationary; however, this work incorporates the effects of atomic vibrations, revealing that this motion introduces new interactions between the atoms. The team demonstrates that these interactions lead to the emergence of a novel phase characterized by broken symmetry, a previously unobserved state in these systems. Furthermore, the study shows that incorporating atomic vibrations suppresses the unusual, non-thermal behavior observed in certain quantum states known as ‘quantum scars’, promoting a return to expected thermal behavior. These findings highlight the significant role of atomic motion in shaping the quantum properties of these arrays and could be directly tested using existing experimental setups. The authors acknowledge that their current model simplifies certain aspects of the system and future work could explore the potential of these vibrations for applications in quantum simulation and computation, potentially serving as robust quantum memory or mediating quantum logic gates.