Central to this investigation is the nature of heating in many-body quantum systems subject to external drives that are not strictly periodic—a scenario that defies traditional Floquet theory frameworks. Conventional wisdom has held that periodically driven systems invariably absorb energy until reaching featureless infinite-temperature states, erasing any interesting quantum correlations. However, the introduction of temporal randomness in driving protocols, meticulously controlled in the experimental setup, challenges this premise, fostering conditions where energy absorption is strongly suppressed. This discovery underscores the expansive potential to exploit intricate driving schemes to stabilize non-equilibrium phases of matter otherwise inaccessible through conventional methodologies.

The experiment’s core strength lies in its ability to perform quantum state tomography (QST) to monitor subsystem entanglement entropy as a real-time probe of dynamical evolution. Entanglement, the enigmatic quantum correlation bridging distinct physical regions, plays a pivotal role in characterizing thermalization and heating processes. The researchers detail how the initially coherent and spatially non-uniform entanglement distribution evolves throughout the prethermal plateau, exhibiting coherent oscillations within selected subsystems. Such spatial heterogeneity and oscillatory behavior provide critical insights into the microscopic mechanisms underpinning entanglement generation and its subsequent propagation, especially in two-dimensional architectures where geometric constraints produce rich, nuanced dynamics.

As time progresses, a notable transition emerges from subsystems exhibiting area-law entanglement scaling—typical of low-entropy or localized states—toward volume-law scaling that characterizes fully thermalized, entropy-saturated many-body states. The advent of heating catalyzes this crossover, accelerating entanglement growth and heralding a departure from the prethermal regime to eventual infinite-temperature equilibration. This dynamic enables a detailed mapping of quantum thermalization in regimes where classical computational techniques fail, affirming the unique role of superconducting processors as powerful platforms for simulating and exploring complex quantum many-body phenomena.

Beyond immediate experimental findings, the study lays a fertile groundwork for future inquiries into the deep complexities governing driven quantum systems. Variations in initial state preparation and spatially heterogeneous energy absorption patterns remain open questions, promising to uncover richer physics. Moreover, the delicate interplay between random driving and phenomena like many-body localization or emergent topological order calls for further theoretical and experimental scrutiny, potentially unveiling novel stabilization mechanisms for exotic quantum phases under temporal disorder.

This research also pushes the frontier in identifying prethermalization mechanisms within a broader class of non-periodic or aperiodic drives, expanding the theoretical landscape and providing a robust experimental benchmark. The universality of these heating suppression effects—demonstrated beyond the particular superconducting platform used—foreshadows their applicability across other quantum simulation architectures, including trapped ions, cold atoms, or photonic systems. Such versatility heralds a new era in the control and engineering of quantum states out of equilibrium.

Intriguingly, the n-RMD protocol’s capacity to balance temporal randomness with controlled energy input offers a blueprint for designing drive sequences that optimize system coherence and minimize deleterious heating. By carefully tailoring drive order and frequency, quintessential physical traits such as prolonged prethermal lifetimes become accessible, facilitating intricate quantum phenomena explorations while maintaining experimental feasibility. These insights could be instrumental in advancing quantum information processing techniques, error correction paradigms, and quantum state manipulation strategies.

At the same time, the success in experimentally realizing system sizes marked by tens of qubits in two-dimensional arrays alleviates historic scalability bottlenecks, bringing quantum simulators into uncharted territories of many-body physics. The comprehensive characterization of entanglement dynamics across spatial and temporal domains paves new paths for benchmarking quantum devices and refining theoretical models. This is particularly impactful since understanding heating and thermalization in complex systems constitutes a fundamental challenge of condensed matter physics and quantum statistical mechanics.

Moreover, the direct observation of prethermalization plateaus and their algebraic lifetimes provides a robust platform to dissect dynamical phase transitions governed by competing timescales and energy scales intrinsic to driven systems. This is a pivotal step toward controlling nonequilibrium steady states, with implications spanning from quantum thermodynamics to material science. Additionally, the work vividly illustrates the profound synergy between experimental advancements in superconducting quantum technology and conceptual progress in dynamical quantum control.

By pushing the envelope of high-fidelity control and measurement capabilities, this study demonstrates that elaborate temporal randomness can be engineered, not as a source of decoherence, but as a lever to unlock new quantum phases with prolonged stability. Such a paradigmatic shift inspires optimism for realizing complex quantum devices capable of robust functionality despite environmental noise and intrinsic drive imperfections.

Finally, this experimental tour de force reaffirms the transformative potential of quantum processors, transcending their primary role in computation to become unparalleled tools for probing fundamental physics. As the quantum community seeks to harness quantum mechanical principles for next-generation technologies, the ability to finely tune dynamical properties will be indispensable. The insights gleaned from this research thus not only deepen our understanding of quantum matter under nonequilibrium conditions but also chart a course for innovative approaches to quantum control in the years to come.

Subject of Research:
Non-equilibrium dynamics and prethermalization in two-dimensional interacting quantum systems driven by random multipolar protocols, explored through quantum state tomography on a 78-qubit superconducting processor.

Article Title:
Prethermalization by random multipolar driving on a 78-qubit processor.

Article References:
Liu, ZH., Liu, Y., Liang, GH. et al. Prethermalization by random multipolar driving on a 78-qubit processor. Nature (2026). https://doi.org/10.1038/s41586-025-09977-x

Image Credits:
AI Generated

DOI:
https://doi.org/10.1038/s41586-025-09977-x

The foundational framework of this research lies in non-Hermitian physics, which describes open quantum systems exchanging energy and information with their surroundings. Unlike closed quantum systems described by Hermitian operators guaranteeing real eigenvalues and thus stable energies, non-Hermitian systems can host exceptional points (EPs). These EPs are unique singularities in parameter space where not only the eigenvalues but the associated eigenvectors simultaneously coalesce, giving rise to rich and often counterintuitive physical phenomena, including chiral state evolution, where the final system state depends intricately on the trajectory taken around such EPs.

Traditionally, chiral dynamics emerging from exceptional points have been analyzed and observed primarily in single-particle or few-particle quantum systems, which are amenable to direct experimental control and theoretical modeling. However, the realization of such non-Hermitian topological effects in genuine many-body systems, especially those involving strong interactions and dissipations, has remained elusive due to the complex interplay of interactions and decoherence. The work by the USTC team closes this crucial gap by engineering a strongly correlated Rydberg atomic ensemble serving as a prototypical many-body open quantum system with tunable parameters.

In their experimental setup, the researchers utilized a room-temperature vapor cell containing Rubidium atoms. The atoms were excited to high-lying Rydberg states by precisely controlled laser fields. These Rydberg states are characterized by exaggerated dipole moments, which engender substantial long-range interactions between atoms, mediating a strongly correlated many-body environment. The continuous laser drive and the inevitable dissipation through spontaneous emission and dephasing render the system inherently non-Hermitian, thus effectively embedding themselves in a dissipative quantum many-body framework.

Key to the observed phenomena is the manifestation of optical bistability within the system—a regime in which the system can stably reside in one of two distinct steady states distinguished by their Rydberg populations and associated optical transmission properties. Crucially, this bistability does not arise from simple metastability or local nonlinearities but instead corresponds to a richer underlying non-Hermitian structure in parameter space. The team demonstrated that the boundary of this bistable region corresponds to a complex exceptional structure comprising exceptional lines, which converge at a higher-order exceptional point, reflecting a sophisticated topology of the system’s dynamical generator, known as the Liouvillian superoperator.

Exploring the parameter landscape constructed from laser detuning and laser power, the researchers employed slow cyclic variations encircling this exceptional structure. Remarkably, they recorded chiral state-switching behavior: traversing the loop in one direction transformed the system from a high optical transmission state to a low transmission state, while reversing the cycle direction restored the original state. This directional dependence is a striking manifestation of the global topological properties of the exceptional structure rather than a trivial hysteresis typically encountered in nonlinear optical systems.

The unique topology of the Liouvillian exceptional structure endows the system with a form of path-dependent memory and control, reminiscent of a molecular-scale “revolving door” that permits state transitions only upon encircling the exceptional structure in a particular direction. This chiral switching differs fundamentally from conventional bistable hysteresis, as the final state depends on a global geometric property of the trajectory in the multi-dimensional control parameter space, reflecting the underlying non-Hermitian topology rather than local local-bistable energy landscape features.

Prof. Wei Yi emphasized that this phenomenon is intrinsically many-body in nature, arising from the collective interactions among the Rydberg atoms and their interplay with coherent driving and dissipation. The many-body effects enrich the topology and spectral properties of the Liouvillian operator governing the system’s time evolution, enabling control paradigms that surpass single-particle scenarios. This non-trivial many-body topological control could pave new pathways for designing quantum devices that exploit dissipative engineering and non-Hermitian dynamics.

The experimental flexibility was further showcased by demonstrating external tunability of the chiral dynamics. By varying the atomic density through temperature control, the researchers modulated the effective interaction strength and dissipation rates, thereby tuning the exceptional structure’s landscape. Additionally, dressing the Rydberg states with microwave fields introduced further control knobs, allowing for modulation of energy levels and interaction pathways. This tunability offers practical avenues for harnessing and exploiting chiral state-switching in future quantum technologies.

The significance of this discovery lies not only in advancing fundamental understanding of non-Hermitian topology in many-body open quantum systems but also in establishing a new paradigm for controlling quantum states dynamically via their non-Hermitian spectral singularities. These insights inform future explorations into dissipative phase transitions, quantum information processing, and the design of novel optical and quantum devices with inherent directionality and robust control via parameter-space topology.

This research bridges experimental quantum optics, atomic physics, and mathematical physics by unveiling how complex exceptional-point structures govern emergent many-body quantum dynamics. By manipulating the topology of the Liouvillian spectrum, the team realized directional switchable states in a Rydberg gas, bringing theoretical predictions of non-Hermitian topological phenomena firmly into the realm of experimental reality. This opens exciting prospects for further exploring how topology, dissipation, and many-body interactions interplay to produce rich quantum phenomena inaccessible in closed or weakly interacting systems.

The experimental observation of chiral switching via encircling exceptional points in a dissipative Rydberg gas thus sets a precedent for future exploration of non-Hermitian many-body systems. It spotlights the importance of topological structures within Liouvillian frameworks and outlines strategic control methods using accessible parameters such as laser characteristics, atomic density, and microwave dressing. This novel approach deepens our grasp of open quantum system dynamics, particularly in strongly interacting regimes, and promises transformative applications in quantum optics and photonic device engineering.

As researchers delve further into the underlying mathematics and physics of these exceptional structures, potential applications include robust quantum memories, direction-dependent optical switches, and sensors with unprecedented sensitivity reliant on non-Hermitian topological features. The emergent control methodology through many-body parameter modulation provides a versatile platform for engineering quantum states with bespoke dynamical behaviors, a crucial step towards practical quantum technologies leveraging the subtle balance between coherence and dissipation.

This pioneering work embodies an elegant synergy between experiment and theory, highlighting how fundamental concepts such as exceptional points and non-Hermitian topology can manifest spectacularly in complex quantum many-body systems. The integration of Rydberg physics with non-Hermitian dynamics opens new horizons for understanding and harnessing quantum phenomena shaped by their environment, interactions, and global parameter-space geometry.

Subject of Research: Experimental observation and control of chiral state-switching in a dissipative Rydberg gas through Liouvillian exceptional structures in non-Hermitian many-body quantum systems.

Article Title: Chiral Switching Between Collective Steady States in a Dissipative Rydberg Gas via Liouvillian Exceptional Topology

News Publication Date: Not explicitly provided

Web References:

• DOI: 10.1016/j.scib.2025.08.051

References: Published in Science Bulletin, University of Science and Technology of China (USTC) research team.

Image Credits: USTC

Keywords

Non-Hermitian physics, exceptional point, chiral state-switching, dissipative quantum systems, Rydberg atoms, Liouvillian exceptional structure, many-body quantum dynamics, optical bistability, quantum topology, open quantum systems, laser-driven atomic vapor, topological control, quantum optics.

A recent breakthrough realized by a collaborative research effort across several prestigious institutions—including Northwestern University, the University of Hong Kong, the Chinese Academy of Sciences, the University of Houston, and Zhejiang University—marks a significant stride forward in this area. The team reported the first exact numerical solution of the spectral function of one-dimensional Bose gases across arbitrary interaction strengths, a longstanding open problem in quantum many-body physics. Utilizing an ingeniously developed multi-label classification algorithm, the researchers successfully decoded the intricate spectral features, including salient singularities at the spectral thresholds. This accomplishment stands as a vital experimental and theoretical verification of the nonlinear Luttinger liquid (NTLL) theory at an unprecedented scale, simulating systems containing up to 4000 particles.

The core theoretical framework underpinning this breakthrough is the Bethe ansatz technique, a powerful method for solving integrable models. The researchers innovated by conceptualizing an algorithm based on the notion of “relative excitations,” which allowed them to elegantly unify the treatment of ground, finite-temperature equilibrium, and nonequilibrium steady states within a consistent computational scheme. A critical advancement involved the introduction of four quantum numbers—denoted as Pm, Np, Pl, and Nl—that possess transparent physical interpretations as quantum labels partitioning the infinitely dimensional Hilbert space into computationally tractable finite-dimensional subspaces. This mathematical stratification substantially enhanced the numerical efficiency without sacrificing accuracy, opening the door to large-scale exact computations previously deemed infeasible.

By leveraging this method, the team delineated the full spectral function of the one-dimensional Bose gas mapped onto the momentum-energy plane. Their results, graphically depicted through contour plots, vividly illustrate how spectral weight evolves with interaction strength. Particularly striking is the manifestation of power-law scaling behaviors near the spectral thresholds, a hallmark predicted by NTLL theory that had eluded verification in systems of comparable size until now. The computed critical exponents exhibited remarkable concordance with theoretical predictions, falling within tight quantitative agreement which lends robust support to the foundational premises of nonlinear Luttinger liquid phenomenology.

Beyond spectral function analysis, the study extended to important correlation functions such as the momentum distribution. Here, distinct regimes emerged, governed respectively by linear TLL theory in the low-momentum limit and Tan’s Contact relationships dominating at high momenta. This duality elegantly encapsulates the interplay between universal low-energy excitations and high-energy short-range correlations, reflecting the nuanced nature of strongly interacting quantum gases. The ability to capture these varied regimes within a single computational framework speaks to the versatility and depth of the multi-label classification approach pioneered by the team.

The significance of these findings transcends mere computational achievement. They provide a new theoretical foundation experimentally accessible via state-of-the-art ultracold atomic platforms, which have steadily advanced in their control and measurement precision. This synergy between exact integrable model results and empirical realizations promises to unlock further mysteries in low-dimensional quantum systems, such as understanding non-equilibrium dynamics, exploring exotic phases, and manipulating quantum information. Moreover, this work paves the way for systematic investigations of other integrable models and extensions involving higher dimensions or additional interaction channels.

Importantly, the algorithmic innovations introduced in this study resonate beyond quantum gases, offering potential applications in broader areas of physics where complex many-body interactions are paramount. The partitioning technique inspired by physical quantum numbers suggests new computational paradigms that reconcile analytical rigor with scalable numerical methods. As quantum simulation and quantum computing technologies mature, such methods will become invaluable for benchmarking and guiding experiments, ultimately bridging the gap between abstract theoretical models and concrete physical systems.

The collaboration behind this breakthrough exemplifies the power of international scientific cooperation, seamlessly integrating expertise in theoretical physics, computational science, and experimental techniques. Supported by major funding agencies, including the National Natural Science Foundation of China, the Hong Kong Research Grants Council, and the Chinese Academy of Sciences, the research sets a high standard for multidisciplinary synergy aimed at unraveling quantum complexity.

Looking ahead, the precise determination of spectral functions and related correlators offers a fertile testing ground for novel quantum technologies. Potential applications span from quantum simulators designed to emulate complex materials to enhanced metrology exploiting many-body entanglement. Additionally, understanding the signature singularities and critical scaling behaviors provides indispensable insights into critical phenomena and phase transitions beyond the conventional paradigms.

In summary, this groundbreaking work elevates our comprehension of one-dimensional strongly correlated Bose gases by harnessing an elegant blend of rigorous integrable model techniques and advanced computational algorithms. The successful validation of nonlinear Luttinger liquid theory predictions in large-scale systems propels the field forward, making concrete strides toward a universal understanding of quantum many-body physics in low dimensions. It stands as a milestone that beckons further theoretical refinement, experimental validation, and technological exploitation in the burgeoning era of quantum science.

Subject of Research: Exact solutions and spectral function characterization of one-dimensional strongly correlated Bose gases using integrable models and multi-label classification algorithms.

Article Title: Precise Determination of Spectral Functions in One-Dimensional Bose Gases Validates Nonlinear Luttinger Liquid Theory at Large Scales

Web References: DOI: 10.1093/nsr/nwaf294

Image Credits: ©Science China Press

Keywords

Quantum many-body physics, one-dimensional Bose gas, spectral function, nonlinear Luttinger liquid, Bethe ansatz, integrable systems, multi-label classification algorithm, strongly correlated systems, ultracold atoms, critical exponents, momentum distribution, Tan’s Contact