MATHEMATICAL SCIENCES

Scientists use superconducting quantum chips to simulate a variety of Chen insulators


The quantum Hall effect is a basic phenomenon in condensed matter physics, and people have developed topological band theory to study such topological states, and found that the band structure of quantum Hall systems is closely related to the boundary state of the system, that is, there is a correspondence between the body phase and the edge, and the use of Chern number to distinguish different topologies, and Chen’s insulator to describe the relevant topological states. Chen insulator materials can be predicted by first-principles calculations, experimentally synthesized and tested, and a series of innovative achievements have emerged in the past few years, and it is expected to develop devices with practical value.

With the development of quantum system regulation technology, various artificial controllable quantum systems have also been used to simulate Chen insulators and reveal their properties. The superconducting quantum computing system has the advantages of stable operation and strong versatility, and will be an ideal platform for simulating Chen insulators.

Recently, Fan Huan, a researcher at the Institute of Physics, Chinese Academy of Sciences, and Xu Kai, an associate researcher, and Xiang Zhongzhong, a joint deputy chief engineer, and other collaborators cooperated to successfully realize the simulation of multiple Chen-type insulators with different Chern numbers by using a ladder-type quantum chip integrating 30 qubits, and demonstrated the body-edge correspondence of theoretical predictions, and the results were published in the journal Nature Communication.

The collaborative team prepared a high-quality quantum chip with 30 bits, and in the experiment, the coupling strength between its qubits was precisely controlled, and the crosstalk between bits was reduced, and the coupling configuration between one-dimensional and ladder-type bits was realized. The simulation scheme designed by the team is to map one dimension of the two-dimensional Chen insulating body point model to the artificial control phase using the Fourier transform, so as to use one-dimensional chained qubits to realize its simulation.

Based on the same idea, the double-layer two-dimensional Chen insulator can be realized by using two one-dimensional chain parallel coupling to form a ladder-type bit-to-bit coupling quantum chip, while the artificial dimensional phase control can also realize different coupling methods of the double-layer Chen insulator. In this way, Chen insulators with different Aged numbers are realized.

A Chern number is a topological invariant used to classify the different topological phases in which a physical system is located. Chen insulator is a two-dimensional topological material with broken time inversion symmetry.

By exciting specific qubits and measuring the energy of different eigenstates, the team directly measured the topological band structure and observed the dynamic characteristics of the boundary local domain of the topological boundary state of the system, and confirmed the body-edge correspondence in the topological band theory on the superconducting quantum simulation platform. In addition, using all 30 qubits, a special topological non-trivial edge state with zero Hall conductance (zero Chen) was experimentally observed for the first time by simulating a double-layer structure Chen insulator on a superconducting quantum simulation platform. In addition, an old insulator with a higher Cherry number was experimentally detected.

This work realizes the reproduction and observation of the topological state properties of quantum many-body systems by accurately controlling the superconducting qubit system and the technical scheme of readout, and also shows the precise controllability of the team’s 30-bit ladder-type coupled superconducting quantum chip. (Source: China Science News Han Yangmei)

Related paper information:Https://doi.org/10.1038/s41467-023-41230-9

30-bit ladder-type quantum chip coupling strength information. (a) Information on the coupling strength between qubits (nearest and sub-nearest neighbors) measured in the 15-bit experiment. (b) Information on the coupling strength between qubits (nearest neighbor, sub-nearest neighbor, and diagonal neighbor) measured in the 30-bit experiment. (Photo courtesy of interviewee)



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