近日，美国谷歌公司研究部门的X. Mi及其团队取得一项新进展。他们对模拟-数字量子模拟器的热化和临界性进行了研究。相关研究成果已于2025年2月5日在国际权威学术期刊《自然》上发表。

该研究团队展示了一个由69个超导量子比特组成的量子模拟器，它同时支持通用量子门和高保真模拟演化，其性能在交叉熵基准测试中超越了经典模拟的能力。与仅支持模拟的模拟器相比，这一混合平台具备更为多样的测量功能。研究人员利用这一优势，揭示了XY模型中由粗化诱导的Kibble-Zurek标度预测失效现象，以及经典Kosterlitz-Thouless相变的特征。

此外，数字门实现了精确的能量控制，使他们能够研究本征谱特定部分中本征态热化假设的效应。他们还展示了成对纠缠二聚体状态的数字制备，并成像了随后在模拟演化过程中能量和涡度的传输。这些结果证明了超导模拟-数字量子处理器在制备多体谱中的状态并揭示其热化动力学方面的有效性。

据悉，理解相互作用粒子如何趋近热平衡是量子模拟器面临的一项重大挑战。要充分发挥这类系统在这一目标上的潜力，需要能够灵活地制备初始状态、精确地进行时间演化以及广泛地探测以表征最终状态。

附：英文原文

Title: Thermalization and criticality on an analogue–digital quantum simulator

Author: Andersen, T. I., Astrakhantsev, N., Karamlou, A. H., Berndtsson, J., Motruk, J., Szasz, A., Gross, J. A., Schuckert, A., Westerhout, T., Zhang, Y., Forati, E., Rossi, D., Kobrin, B., Paolo, A. Di, Klots, A. R., Drozdov, I., Kurilovich, V., Petukhov, A., Ioffe, L. B., Elben, A., Rath, A., Vitale, V., Vermersch, B., Acharya, R., Beni, L. A., Anderson, K., Ansmann, M., Arute, F., Arya, K., Asfaw, A., Atalaya, J., Ballard, B., Bardin, J. C., Bengtsson, A., Bilmes, A., Bortoli, G., Bourassa, A., Bovaird, J., Brill, L., Broughton, M., Browne, D. A., Buchea, B., Buckley, B. B., Buell, D. A., Burger, T., Burkett, B., Bushnell, N., Cabrera, A., Campero, J., Chang, H.-S., Chen, Z., Chiaro, B., Claes, J., Cleland, A. Y., Cogan, J., Collins, R., Conner, P., Courtney, W., Crook, A. L., Das, S., Debroy, D. M., Lorenzo, L. De, Barba, A. Del Toro, Demura, S., Donohoe, P., Dunsworth, A., Earle, C., Eickbusch, A., Elbag, A. M., Elzouka, M., Erickson, C., Faoro, L., Fatemi, R., Ferreira, V. S.

Issue&Volume: 2025-02-05

Abstract: Understanding how interacting particles approach thermal equilibrium is a major challenge of quantum simulators. Unlocking the full potential of such systems towards this goal requires flexible initial state preparation, precise time evolution and extensive probes for final state characterization. Here we present a quantum simulator comprising 69 superconducting qubits that supports both universal quantum gates and high-fidelity analogue evolution, with performance beyond the reach of classical simulation in cross-entropy benchmarking experiments. This hybrid platform features more versatile measurement capabilities compared with analogue-only simulators, which we leverage here to reveal a coarsening-induced breakdown of Kibble–Zurek scaling predictions in the XY model, as well as signatures of the classical Kosterlitz–Thouless phase transition. Moreover, the digital gates enable precise energy control, allowing us to study the effects of the eigenstate thermalization hypothesis in targeted parts of the eigenspectrum. We also demonstrate digital preparation of pairwise-entangled dimer states, and image the transport of energy and vorticity during subsequent thermalization in analogue evolution. These results establish the efficacy of superconducting analogue–digital quantum processors for preparing states across many-body spectra and unveiling their thermalization dynamics.

DOI: 10.1038/s41586-024-08460-3

Source: https://www.nature.com/articles/s41586-024-08460-3