Quantum Critical Dynamics Achieves Universal Scaling with 120 Qubit Processors
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The behaviour of systems undergoing rapid change near critical points is a fundamental problem in physics, with implications for technologies ranging from materials science to quantum computing. Brendan Rhyno, Swarnadeep Majumder, Smitha Vishveshwara, and colleagues at the University of Illinois at Urbana-Champaign, IBM Quantum, and MIT investigate how imperfections, specifically noise, affect these critical transitions in digital quantum processors.
The team demonstrates that even with significant noise, clear and predictable scaling relationships emerge during these transitions, revealing a surprising persistence of universal behaviour.
This research challenges existing theoretical predictions and suggests that noise doesn’t simply destroy the expected patterns, but instead shapes a new, distinct regime of universality, offering a novel way to characterise and assess quantum hardware beyond traditional performance metrics.
Quantum Quench Dynamics and Hardware Noise This supplementary material details research investigating the behaviour of a quantum system, specifically the transverse field Ising model, as it undergoes a rapid change near a critical point. Researchers combined theoretical simulations with experiments performed on IBM Quantum hardware to understand how hardware noise affects observed behaviour and whether universal predictions still hold true.
The team carefully considered practical aspects of the quantum hardware experiments, utilizing 220 measurements to achieve a standard error of approximately 10^-3 in key quantities like local magnetization and correlations. Minimal error mitigation techniques, including Pauli twirling and dynamical decoupling, were employed to focus on the inherent noise of the hardware. Extensive experimental data showcases the dynamics of equal-time connected spin-spin correlation functions for systems containing up to 20 qubits. Analyses over multiple dates and with varying qubit numbers, 100 and 120, demonstrate consistent results. The findings confirm the presence of noise, leading to differences in fitted scaling exponents compared to theoretical predictions. Despite this noise, re-scaled data consistently collapses, indicating that universal behaviour persists even in the presence of decoherence. This suggests that the experimental setup effectively controlled for standard errors and that the minimal error mitigation strategy successfully isolated the effects of inherent hardware noise. Simulating and Observing Kibble-Zurek Dynamics in Qubits This study investigated the impact of noise on critical dynamics in quantum systems undergoing rapid change, employing both numerical simulations and experiments on superconducting quantum processors. Researchers first performed extensive simulations of spin chains, systematically varying noise strength to understand its influence on universal scaling behaviour predicted by the Kibble-Zurek mechanism. These simulations provided a precise benchmark for interpreting experimental results obtained on superconducting processors containing between 80 and 120 qubits.
The team studied linear quenches in the transverse-field Ising model, measuring equal-time connected correlations, defect densities, and excess energies across a range of quench times. Surprisingly, clear scaling relations emerged despite the presence of noise, indicating persistent universal structure shaped by decoherence. Detailed analysis of extracted scaling exponents revealed discrepancies from both ideal theoretical predictions and simplified noise models. This suggests the emergence of a distinct noise-influenced universality regime, where noise actively reshapes universal behaviour rather than simply masking it. The innovative experimental setup leveraged the capabilities of advanced superconducting processors, enabling the exploration of complex quantum dynamics beyond the reach of classical simulations. This approach opens the possibility of using universal dynamical scaling as a high-level descriptor of quantum hardware performance, complementing traditional gate-level metrics. Kibble-Zurek Mechanism Verified in Superconducting Qubits This work presents a detailed investigation into how noise impacts the universal scaling predicted by the Kibble-Zurek mechanism during rapid changes in a quantum system. Researchers utilized digital superconducting quantum processors, specifically an IBM Fez Heron processor with 156 qubits, to simulate the one-dimensional transverse field Ising model, a standard system for studying quantum phase transitions. Experiments involved driving the system through a critical point at varying rates and measuring the resulting defect density and excess energy.
The team successfully performed simulations on systems ranging from 80 to 120 qubits, meticulously measuring equal-time connected correlations, defect densities, and excess energies across a range of quench times. Surprisingly, clear scaling relations emerged despite the presence of noise, indicating persistent universal structure shaped by decoherence, unlike previous observations where noise masked these behaviours. The results demonstrate that the extracted scaling exponents deviate from both ideal Kibble-Zurek predictions and those derived from simplified noise models. This suggests the emergence of a distinct noise-influenced universality regime. Measurements confirm that the observed exponents are modified compared to standard Kibble-Zurek predictions and values reported under nondemolishing noise, extending beyond the capabilities of classical simulations. The study’s findings suggest that universal dynamical scaling can serve as a high-level descriptor of quantum hardware performance, complementing conventional gate-level metrics, and providing a new avenue for characterizing and optimizing quantum systems.
Noise Alters Universal Quantum Dynamical Scaling This research demonstrates that noise fundamentally alters universal scaling behaviour observed during rapid changes in quantum systems, offering new insights into how these systems evolve. By examining the dynamics of spin chains and implementing experiments on superconducting processors with up to 120 qubits, scientists observed clear scaling relations even in the presence of noise, challenging previous findings where noise obscured universal behaviour. The extracted scaling exponents differed from both ideal theoretical predictions and simplified noise models. This indicates the emergence of a distinct universality regime influenced by noise. These findings suggest that universal dynamical scaling can serve as a valuable high-level descriptor of quantum hardware, complementing traditional gate-level performance metrics.
The team distinguished deviations from ideal quantum dynamics, providing a quantitative method for characterizing effective universality classes associated with different quantum platforms. While the study focused on one-dimensional systems, the approach readily extends to two-dimensional systems, potentially enabling exploration of geometry-dependent dynamics and new universality classes. Future work in this area could not only test quantum advantage in nonequilibrium dynamics but also establish a unifying framework for comparing quantum simulators across diverse architectures and spatial dimensions. 👉 More information 🗞 Quantum critical dynamics and emergent universality in decoherent digital quantum processors 🧠 ArXiv: https://arxiv.org/abs/2512.13143 Tags: