Information scrambling in quantum circuits

Creators: Mi, Xiao; Roushan, Pedram; Quintana, Chris; Mandrà, Salvatore; Marshall, Jeffrey; Neill, Charles; Arute, Frank; Arya, Kunal; Atalaya, Juan; Babbush, Ryan; Bardin, Joseph C.; Barends, Rami; Basso, Joao; Bengtsson, Andreas; Boixo, Sergio; Bourassa, Alexandre; Broughton, Michael; Buckley, Bob B.; Buell, David A.; Burkett, Brian; Bushnell, Nicholas; Chen, Zijun; Chiaro, Benjamin; Collins, Roberto; Courtney, William; Demura, Sean; Derk, Alan R.; Dunsworth, Andrew; Eppens, Daniel; Erickson, Catherine; Farhi, Edward; Fowler, Austin G.; Foxen, Brooks; Gidney, Craig; Giustina, Marissa; Gross, Jonathan A.; Harrigan, Matthew P.; Harrington, Sean D.; Hilton, Jeremy; Ho, Alan; Hong, Sabrina; Huang, Trent; Huggins, William J.; Ioffe, L. B.; Isakov, Sergei V.; Jeffrey, Evan; Jiang, Zhang; Jones, Cody; Kafri, Dvir; Kelly, Julian; Kim, Seon; Kitaev, Alexei; Klimov, Paul V.; Korotkov, Alexander N.; Kostritsa, Fedor; Landhuis, David; Laptev, Pavel; Lucero, Erik; Martin, Orion; McClean, Jarrod R.; McCourt, Trevor; McEwen, Matt; Megrant, Anthony; Miao, Kevin C.; Mohseni, Masoud; Montazeri, Shirin; Mruczkiewicz, Wojciech; Mutus, Josh; Naaman, Ofer; Neeley, Matthew; Newman, Michael; Niu, Murphy Yuezhen; O'Brien, Thomas E.; Opremcak, Alex; Ostby, Eric; Pato, Balint; Petukhov, Andre; Redd, Nicholas; Rubin, Nicholas C.; Sank, Daniel; Satzinger, Kevin J.; Shvarts, Vladimir; Strain, Doug; Szalay, Marco; Trevithick, Matthew D.; Villalonga, Benjamin; White, Theodore; Yao, Z. Jamie; Yeh, Ping; Zalcman, Adam; Neven, Hartmut; Aleiner, Igor; Kechedzhi, Kostyantyn; Smelyanskiy, Vadim; Chen, Yu

Abstract

Interactions in quantum systems can spread initially localized quantum information into the exponentially many degrees of freedom of the entire system. Understanding this process, known as quantum scrambling, is key to resolving several open questions in physics. Here, by measuring the time-dependent evolution and fluctuation of out-of-time-order correlators, we experimentally investigate the dynamics of quantum scrambling on a 53-qubit quantum processor. We engineer quantum circuits that distinguish operator spreading and operator entanglement and experimentally observe their respective signatures. We show that whereas operator spreading is captured by an efficient classical model, operator entanglement in idealized circuits requires exponentially scaled computational resources to simulate. These results open the path to studying complex and practically relevant physical observables with near-term quantum processors.

Additional Information

© 2021 American Association for the Advancement of Science. Received 9 January 2021; accepted 19 October 2021. Published online 28 October 2021. P.R. and X.M. acknowledge fruitful discussions with P. Zoller, B. Vermersch, A. Elben, and M. Knapp. S.Ma. and J.Ma. acknowledge support from the NASA Ames Research Center and support from the NASA Advanced Supercomputing Division for providing access to the NASA HPC systems, Pleiades and Merope. S.Ma. and J.Ma. also acknowledge support from the AFRL Information Directorate under grant no. F4HBKC4162G001. J.Ma. is partially supported by NAMS contract no. NNA16BD14C. S.Ma. is also supported by the Prime contract no. 80ARC020D0010 with the NASA Ames Research Center. Author contributions: V.Sm., K.K., X.M., and P.R. devised the experiment. X.M., C.Q., and P.R. executed the experiment on the Google quantum hardware. X.M., P.R., K.K., and Y.C. wrote the manuscript. X.M., S.Ma., J.Ma., and K.K. wrote the supplementary materials. V.Sm., I.A., X.M., K.K., S.Ma., and J.Ma. provided theoretical support, analysis techniques, and numerical computations. I.A. and K.K. developed the Markov process model. S.Ma. designed and performed the large-scale numerical simulation, including the algorithms and software development. J.Ma. performed the noisy numerical simulations. P.R., Y.C., V.Sm., and H.N. led and coordinated the project. Infrastructure support was provided by the Google Quantum AI hardware team. The NASA Advanced Supercomputing Division at NASA Ames provided the infrastructure to run high-performance computing (HPC) simulations. All authors contributed to revising the manuscript and the supplementary materials. The authors declare no competing interest. Data and materials availability: All experimental and numerical data in the main text and supplementary materials, along with the software code for generating quantum circuits, measurements, population dynamics simulation, and tensor contraction simulation are available at Zenodo (43).

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