The creation of a universal quantum computer is one of the most difficult tasks of modern physics. It will fundamentally change humanity's ideas about the Internet and methods of transmitting information, cybersecurity and cryptography, electronic currencies, artificial intelligence and machine learning systems, methods for synthesizing new materials and drugs, and modeling approaches complex physical, quantum and ultra-large (big data) systems.
The exponential increase in dimension when trying to calculate real systems or the simplest quantum systems is an impossible obstacle for classical computers. However, in 1980, Yuri Manin and Richard Feynman (in 1982, but in more detail) independently put forward the idea of using quantum systems for calculations.
In 1994, Peter Shor proposed a quantum algorithm for decomposing numbers into prime factors. The question of the existence of an effective classical solution to this problem is extremely important and is still open, while the Shor’s algorithm provides exponential acceleration relative to the best classical analog.
In 1996, Lov Grover proposed a quantum algorithm for solving the problem of search with quadratic acceleration. Despite the fact that the acceleration of the Grover’s algorithm is noticeably lower than the Shore algorithm, its wide range of applications, and the obvious impossibility of accelerating the classical version of the search, are important. Today, more than 40 efficient quantum algorithms are known, most of which are based on the ideas of the Shor and Grover’s algorithms, the implementation of which is an important step toward creating a universal quantum computer.
The implementation of quantum algorithms is one of FMN Laboratory’s priority tasks. In this area, our researches are focused on developing multi-qubit superconducting quantum integrated circuits for the creation of universal quantum information processing systems and quantum simulators. The basic element of such schemes are Josephson tunnel junctions consisting of two superconductors separated by a thin barrier – an isolator about one nm thick. Superconducting qubits based on Josephson junctions when cooled in dissolution cryostats to almost absolute zero temperature (~20 mK) exhibit quantum-mechanical properties, demonstrating quantization of electric charge (charge qubits), phase or magnetic field flux (flux qubits) depending on their design.
To combine qubits into circuits, capacitive or inductive connecting elements, as well as superconducting coplanar resonators, are used. Microwave pulses with controlled amplitude and phase carry out the control. Superconducting circuits are particularly attractive because they can be manufactured by planar mass technologies used in the semiconductor industry. At FMN Laboratory, we use equipment (R&D class) from leading manufacturers, specially designed and created for us, taking into account the peculiarities of technological processes for the manufacture of superconducting quantum integrated circuits.
Despite the fact that the quality indicators of superconducting qubits have grown by almost several orders of magnitude over the past 15 years, superconducting quantum integrated circuits are still very unstable compared to classical processors. Building a reliable universal multi-qubit quantum computer requires solving a large number of physical, technological, architectural, and algorithmic problems.
At FMN Laboratory, we have developed a comprehensive program of research and development in the direction of creating multi-qubit superconducting quantum circuits, including:
- Methods of formation and research of new materials and interfaces
- Design and manufacturing technology of elements of quantum circuits
- Scalable manufacturing of highly coherent qubits and high-Q resonators
- Tomography (the measurement of characteristics) of superconducting qubits
- Control of superconducting qubits, quantum switching (entanglement)
- Detection methods and error correction algorithms
- Architecture development of multi-qubit quantum circuits
- Superconducting parametric amplifiers with a quantum noise level
The FMN Laboratory team has developed an aluminum technology for the formation of Josephson Al – AlOx – Al transitions with minimum sizes in the range of 100–500 nm and reproducibility of the transition parameters by a critical current of no worse than 5%. Ongoing technological research is aimed at finding new materials, improving technological operations for the formation of transitions, approaches to the integration with new route technological processes and increasing the reproducibility of manufacturing transitions with an increase in their number to tens of thousands of pieces per crystal.
Highly coherent superconducting qubits
At FMN Laboratory, we develop, manufacture and test charge and flow qubits of various designs (flow, flaxoniums, 2D / 3D transmons, X-monons, etc.) with aluminum Josephson junctions. We conduct research on new materials and methods for creating highly coherent qubits, aimed to improve the basic parameters of superconducting qubits.
High-Q superconducting resonators
We are developing thin-film transmission lines and high-quality superconducting resonators with resonant frequencies in the range of 3-10 GHz. We use them in elements of quantum circuits and memory for quantum computing, providing control of individual qubits, communication between them and reading of their states in real-time. The main task here is to increase the quality factor of the created structures in a single-photon mode at low temperatures.
In order to increase the parameters of superconducting resonators, we conduct research on various types of their structures, thin-film materials (aluminum, niobium, and niobium nitride), film deposition methods (electron beam, magnetron, and atomic layer) and topology formation (explosive lithography, various etching processes) on various substrates (silicon, sapphire) and the integration of various materials in one scheme.
Electrodynamics of quantum circuit elements
QED schemes are extremely attractive both from the point of view of studying the features of the interaction of various elements of quantum systems, and the creation of quantum devices for practical use. We study various types of interaction schemes for elements of QED schemes: effective coupling of qubits and control elements, circuitry solutions for entangling qubits, quantum nonlinearity of interaction of elements with a small number of photons, etc. These studies help to create a base of practical experimental methods for creating multi-qubit quantum integrated circuits.
Multi-qubit quantum integrated circuits
The main goal of research in this direction is to develop a technology for creating the metrological, methodological and algorithmic base for implementing Shor’s and Grover’s algorithms using multi-qubit quantum circuits and demonstrating quantum acceleration compared to classical supercomputers. This ambitious scientific and technical task requires solving a huge number of theoretical, physical, technological, circuitry, metrological and algorithmic problems, which are currently actively working on leading scientific groups and IT companies.
Research and development in the field of quantum computing is carried out in close cooperation with leading Russian research teams of the Institute of Physics and Technology of the Russian Academy of Sciences, MISIS, MIPT, NSTU and the RQC under the supervision of world-famous Russian scientists.