NISQ Simulators Discover Novel Quantum Dynamics, Advancing Understanding of Complex Physics after Four Decades

Understanding the behaviour of interacting systems represents a central challenge in modern physics, as many technological advances rely on comprehending these complex scenarios. Pedram Roushan and Leigh S. Martin, both from Google, investigated whether current quantum simulators are capable of revealing previously unknown physical phenomena, building on Richard Feynman’s long-held vision of using controllable quantum systems to model complex problems. Their work demonstrates that these simulators have, in several instances, advanced our understanding of complex dynamics, achieving insights that, while theoretically possible, were first realised using quantum processors. This finding encourages further exploration, suggesting that quantum simulators are already beginning to challenge and refine established scientific understanding. NISQ Devices Reveal Unexpected Quantum Dynamics This work highlights how Noisy Intermediate-Scale Quantum (NISQ) devices are contributing to scientific discovery, moving beyond simply demonstrating quantum computation. The authors present examples where NISQ experiments have yielded insights not readily obtainable through classical methods or existing theoretical understanding, categorizing these discoveries into three main areas. Firstly, NISQ devices are observing unexpected dynamics that challenge or refine existing theoretical models, such as quantum many-body scarring, where systems exhibit persistent oscillations in excited states, defying typical thermalization. Researchers are also observing robust bound states in perturbed systems, unexpectedly stable even with significant disturbances, contradicting predictions from Fermi’s Golden Rule. Furthermore, these devices reveal faster-than-linear growth of correlations, indicating a propagation of information faster than predicted by standard models. Secondly, NISQ experiments are being used to verify or challenge theoretical predictions, sometimes confirming them and sometimes revealing discrepancies. For example, experiments confirm the applicability of Kardar-Parisi-Zhang (KPZ) universality to the dynamics of one-dimensional Heisenberg spin chains, but also reveal deviations from the theory under certain conditions, particularly closer to equilibrium. Finally, NISQ devices are enabling the measurement of physical parameters in complex materials, like the Fermi-Hubbard model, that are difficult to calculate classically. Researchers are measuring spin diffusion coefficients and resistivity in a challenging parameter regime, potentially shedding light on high-temperature superconductivity. These experiments demonstrate that NISQ devices are generating new scientific insights, allowing researchers to undertake exploratory experiments, and shifting the burden of proof to demonstrate that observed dynamics are not artifacts of the noisy hardware. The authors anticipate that NISQ devices will increasingly lead the path of discovery, eventually exceeding the capabilities of classical computers in certain areas, emphasizing the importance of continued investment in both hardware and theoretical development. In essence, the paper argues that NISQ devices are no longer just tools for testing theories, but are becoming instruments for making discoveries. NISQ Processors Simulate Quantum Many-Body Systems Scientists are increasingly turning to quantum processors to investigate complex physical systems, building on the foundational work initiated decades ago by Richard Feynman who proposed using controllable quantum devices to simulate less understood quantum systems. This work leverages advances in manipulating large, interacting quantum systems, moving beyond the simplification of treating particles as independent entities, a common approach in traditional physics. Researchers currently employ moderately-sized NISQ (Noisy Intermediate-Scale Quantum) processors, achieving control over individual quantum degrees of freedom such as superconducting qubits, atoms, and crystalline defects. This study pioneers a methodology where these NISQ processors are used not simply to confirm existing theories, but to explore regimes where conventional computational methods fail, particularly in understanding the behavior of highly entangled systems. Experiments employ stroboscopic, or digital, and analog time evolution techniques to simulate quantum dynamics, allowing scientists to observe phenomena inaccessible to classical computers due to the exponential growth in computational complexity. This approach enables investigation of non-equilibrium quantum phases of matter, where interactions between particles are crucial and single-particle approximations are inadequate. Recent work demonstrates the power of this methodology through the successful observation and characterization of many-body localization and time crystalline behavior. Scientists meticulously control and measure the quantum states of these systems, validating the performance of the processors and identifying key limitations. These experiments, while often reproducing known phenomena, progressively increase in complexity, pushing the boundaries of what is computationally feasible and providing crucial insights into the behavior of complex quantum systems.

Quantum Scars Stabilized by Periodic Driving Recent work demonstrates that quantum simulators are not merely validating existing theories, but are actively driving new discoveries in complex physical systems. Researchers have observed phenomena on these platforms that were previously unknown, offering insights into non-equilibrium dynamics and challenging conventional wisdom. One notable example involves the observation of “quantum many-body scars” in a one-dimensional chain of atoms, where the system unexpectedly exhibited periodic revivals of an initial state, defying the expectation of monotonic relaxation to thermal equilibrium. Experiments revealed that these oscillations could be stabilized through periodic driving, prompting ongoing investigation into the conditions under which such scars appear. Further studies using superconducting circuits demonstrated resilient bound states in a system initially designed to be integrable, but perturbed to break that integrability. Simulations revealed that these photon bound states, expected to decay rapidly with perturbation, exhibited unexpectedly slow decay rates. Numerical studies confirm these findings, yet a comprehensive explanation for this behavior remains elusive, prompting further analytical and numerical investigation. Additionally, researchers observed faster-than-linear propagation of quantum correlations in spin chains with tunable interaction range, simulated using trapped 171Yb ions. This behavior, observed for relatively short-range interactions, challenges current understanding of correlation propagation and lacks a clear consensus explanation. Quantum simulators are also playing an active role in testing scientific conjectures, particularly regarding universal aspects of dynamics in one-dimensional quantum magnets. Experiments studying magnetic domain-wall relaxation in a chain of 87Rb atoms and superconducting qubits confirmed that the first three moments of transferred magnetization align with predictions from the Kardar-Parisi-Zhang (KPZ) equation. However, deviations from KPZ predictions were observed when starting with initial states closer to equilibrium, and analysis of the fourth moment revealed further discrepancies, suggesting that current theoretical models may be inadequate to fully describe the dynamics of Heisenberg spin chains. These findings highlight the potential of quantum simulators to refine our understanding of complex quantum systems and push the boundaries of theoretical physics.

Quantum Simulation Reveals Unexpected Dynamic Behaviour Recent investigations demonstrate that programmable quantum simulators are beginning to yield novel insights into complex physical phenomena, extending beyond the capabilities of traditional theoretical or numerical approaches in certain areas. Researchers have successfully employed these simulators to explore dynamics in systems where interactions between components are crucial, achieving results that refine existing understanding. Specifically, studies have revealed unexpected behaviours in areas such as the persistence of bound states despite perturbations, faster-than-linear growth of correlations, and the observation of dynamics consistent with the Kardar-Parisi-Zhang (KPZ) universality class. 👉 More information 🗞 Discovering novel quantum dynamics with NISQ simulators 🧠 ArXiv: https://arxiv.org/abs/2512.08293 Tags: