MISiS, RCC and Karlsruhe Institute of Technology: Quantum Sensor

Main article: Quantum Computer and Quantum Communication

2021: Quantum Sensor Development

Scientists at NITU MISiS, the Russian Quantum Center and the Karlsruhe Institute of Technology have developed a quantum sensor that allows detecting defects in the work of quantum systems. The development could be a step towards creating a full-fledged quantum computer. This was announced by NITU MISiS on March 3, 2021.

A quantum computer is a device that stores and processes information within a group of quantum systems, each of which is usually two-level and is called a "quantum bit" or "qubit" (eng. 'qubit' - quantum bit). A promising type of qubit for March 2021 is considered superconducting qubits based on Josephson contacts. On their basis, quantum computing devices are most often developed. It is on Josephsonian qubits that the quantum processors of technology companies IBM and Google work.

The key element of superconducting qubits is Josephson contact from several tens to several hundred nanometers in size. It is two layers of conductor (superconducting metal) separated by a thin layer of dielectric, most often alumina.

At the same time, such a method of "assembling" superconducting qubits inevitably leads to the appearance of so-called two-level defects that affect their behavior and lead to errors in calculations. This is due to the fact that technology does not allow to achieve 100% accuracy in the creation of qubits. As a result of the presence of defects, decoherence occurs - the loss of quantum state by qubits, and the inevitable errors due to this.

Two-level defects in alumina and on the surface of superconductors are an important mechanism for generating fluctuations and energy losses in superconductor qubits, thereby effectively limiting the possibility of using such qubits to perform long quantum algorithms.

The more defects occur in the material, and the more they affect the qubits, the more errors are obtained in the calculations.

The quantum sensor developed by scientists allows you to determine the exact location and concentration of two-level defects in qubit chips. According to one of the authors of the study, the head of the laboratory "Superconducting Metamaterials" of NITU "MISiS" and the head of the group at the RCC, Professor, Doctor of Medical Sciences Alexei Ustinov, the sensor sensor itself is a superconductor qubit and allows you to detect individual defects and even manipulate them.

According to scientists, traditional methods for studying the quality of materials, such as X-ray scattering, are not too sensitive to small point defects, and their results often do not make it possible to understand whether developers are moving in the right direction precisely in terms of creating the best qubits. The proposed approach opens up opportunities for the development of dielectrics and superconducting materials with low losses, necessary for the development of quantum computers.