Nature Chinese scientists realize first topological time crystal quantum simulation in superconducting system
In collaboration with Wang Zhen and Wang Haohua's research groups at the School of Physics, Zhejiang University, Deng Dongling's research group at the Institute of Cross-Information, Tsinghua University has experimentally realized the first fully digital quantum simulation of topological time crystals in superconducting systems. The resulting paper, "Digital quantum simulation of Floquet symmetry-protected topological phases," was recently published as an Article in Nature.
Schematic diagram of topological time crystals
The concept of time crystals was first proposed by Nobel Prize winner in physics, Professor Frank Wilczek, in 2012. The familiar crystals, such as diamond and quartz, are composed of atoms that are arranged periodically in space, breaking the continuous spatial translational symmetry. Time crystals extend the characteristics of "crystals" to the time dimension, i.e., some properties of the system repeat periodically in time, breaking the translational symmetry of time. The topological time crystals, however, have special topological properties that break the time translation symmetry only at the boundary of the system.
The study of time crystals has important fundamental theoretical significance and potential application value. Since this concept was proposed, time crystals have made important progress both theoretically and experimentally. On the theoretical side, scientists have proposed the concept of discrete time crystals and elucidated how to realize time crystals in period-driven quantum many-body localized systems. On the experimental side, international research teams have observed discrete-time crystals on quantum platforms such as ion traps, diamond color centers, nuclear magnetic resonance, cold atoms, and superconductors, respectively.
Topology is a branch of mathematics that focuses on spatial properties that are invariant under continuous deformation. For example, a donut can take the shape of a coffee cup by continuous deformation. Therefore, a donut and a coffee cup are exactly equivalent in the topological sense. Physicists have found that many quantum phases and their transitions to each other can be characterized by the concept of topology, and quantum phases with non-trivial topology tend to exhibit physical properties at the edges of the system that are quite different from those inside the system. Combining the concept of topology with time crystals yields topological time crystals. This is a novel form of matter.
Realizing topological time crystals is a very challenging challenge. Dongling Deng's research group at Tsinghua University proposed a theoretical model of topological time crystals and found an optimization scheme for digital quantum simulation of topological time crystals by artificial intelligence algorithms. The research group has successfully observed this novel phenomenon experimentally in collaboration with the superconducting quantum computing team of Zhejiang University.
Diagram of the main experimental results of a superconducting quantum chip simulating a topological time crystal
A one-dimensional chain of 26 superconducting quantum bits is experimentally simulated, and the dynamics of time-shift symmetry is observed to be broken only at the boundary of the system (both ends of the chain) during the evolution of about 240 layers of quantum lines. This is the core feature of topological time crystals that differs from the previously reported conventional time crystals. The combination of topology and time crystals constructs a new kind of non-equilibrium matter phase, which enriches the variety of time crystals and expands the understanding of the quantum world. The superconducting quantum chip used in the experiment adopts an easily scalable nearest-neighbor connectivity architecture with high programming flexibility, which can be used to explore more exotic quantum phenomena.
Corresponding authors of the paper are Dongling Deng, Assistant Professor, Institute of Cross-Information, Tsinghua University, and Zhen Wang, Distinguished Research Fellow, School of Physics, Zhejiang University. Wenjie Jiang, a 2019 PhD student at the Institute of Cross-Information, and Xue Zhang and Jinfeng Deng, PhD students at Zhejiang University, are co-authors of the article. Other authors include some other members of the superconducting quantum computing team at Zhejiang University, as well as Prof. Alexey V. Gorshkov of the University of Maryland, Dr. Fangli Liu (now at QuEra), Prof. Thomas Iadecola of Iowa State University, and Prof. Zhexuan Gong of Colorado School of Mines.
The project was supported by the National Natural Science Foundation of China, the National Key Research and Development Program, a start-up grant from Tsinghua University, and the Shanghai Institute of Terminology.
