Researchers have built an electrical circuit that can retain quantum information over time, which may improve the performance of future quantum computing
Quantum mechanics describes the behavior of nature on a very small scale, and the world of quantum computing aims to use it for advanced and fast data processing. Its main operating principle is superposition - a quantum phenomenon in which one system can be in two states at the same time. In the quantum computer, this system is the qubit - the quantum bit (unit of information) - which can be both 0 and 1 at the same time (as opposed to the bits in the classical computer which can be in one state of operation at a time, 0 or 1). Therefore it has tremendous computational potential.
In the last 20 years, a technological-scientific race has begun to build quantum computing, and countries and giant companies (such as Google, Microsoft, Amazon and IBM) have begun to invest a lot of effort in its development. The main infrastructure of this computing is superconducting electric circuits (which conduct electric current without resistance). When they are cooled to zero degrees, they behave quantumly. This is also how a connection is made between qubit and qubit, which enables the formation of quantum computing.
Dr. Michael Stern from the Physics Department at Bar Ilan University and his team are building superconducting electrical circuits (that is, the basis of the future quantum computer) and trying to improve their properties. This is to keep as long as possible the quantum information resulting from the electrical circuits (for example the flow of electrons in the circuit, clockwise, counterclockwise or in both directions at the same time) and its stability, so that it is not lost.
According to Dr. Stern, "The quantum calculation should be as stable as possible, otherwise the quantum information is lost. That is why we are trying to build new types of qubits and improve them and the electrical circuits that flow in them so that the quantum information is preserved as long as possible. In addition, we try to connect to microscopic external systems, outside the superconducting quantum circuits. These systems are impurities (foreign atoms) within a semiconductor, such as a silicon crystal. These impurities have tremendous potential for storing quantum information. They can keep it almost indefinitely and when necessary transfer it back to the qubits, like the tape (BUS) that connects the processor to the memory in the classic computer."
In one of their latest studies, which won a research grant from the National Science Foundation, the researchers developed a flux qubit that includes a superconducting circuit that consists of a silicon substrate topped with aluminum fans. In addition, it includes several Josephson junctions - a central component in the infrastructure of any superconducting quantum computer, which consists of two aluminum units (superconductors) with a thin layer of oxide (insulating material) between them. Thus they created a macroscopic electric current circuit that can move simultaneously to the right and to the left (superposition mode), clockwise or counterclockwise. At the same time, the researchers built a resonator circuit - a superconducting electric circuit that is based on aluminum and makes it possible to read the state of the qubit (that is, if the electric circuit inside it moves in one or two directions, or in both directions at the same time); This circuit is coupled to the qubit, its frequency changes according to its state, and thus it is possible to know if the qubit is working correctly and preserving the quantum information.
The researchers produced about 30 such qubits, and using a resonator circuit measured their function and measured the length of time they behaved quantumly and retained the quantum information. This is how they discovered that this information was able to be saved for 30 microseconds.
The researchers produced about 30 such qubits, and using a resonator circuit measured their function and measured the length of time they behaved quantumly and retained the quantum information. This is how they discovered that this information was able to be preserved for 30 microseconds - coherence (the duration of the superposition) is prolonged compared to that which exists today (five times). In the next step, they plan to attach the new qubit to impurities inside diamond and silicon crystals and test how well they can preserve the quantum information. Thus they hope to continue building a solid and reliable foundation for quantum computing.
Life itself:
Dr. Michael Stern, 45 years old, lives in Givat Shmuel, married + four daughters (19-9), immigrated to Israel from France when he was 24 years old. He earned a bachelor's and master's degree in electrical engineering at the CentraleSupelec university institution in Paris and a third degree in semiconductor optics at the Weizmann Institute of Science. He did his postdoctoral research in the field of superconducting circuits at the Institute of Atomic Energy (CEA) in Paris. He then established the Laboratory for Hybrid Quantum Systems at Bar Ilan University, and today most of his time is devoted to its management.
