Caught a microwave: quantum memory will help track down stealth drones

A prototype of a quantum RAM device has been created in Russia, a chip that stores the state of quantum signals and is able to reproduce them on demand. The development will allow the implementation of advanced error correction algorithms that improve the accuracy of operations. Quantum chips will also find applications in next‑generation radar systems capable of detecting stealth drones that are invisible to traditional tracking devices. In addition, they can be used in astrophysical instruments that will allow studying the surface of exoplanets at a distance of tens of light-years.

How to save quantum information

Scientists from the Quantum Park cluster of the Bauman Moscow State Technical University and the All-Russian Scientific Research Institute of Automation named after N. L. Dukhov have developed a prototype of a controlled quantum memory. The device can store the signals "packaged" in microwave pulses and reproduce them without loss of information.

— The quantum memory chip is a system of resonator "cells" that operate at different frequencies of the microwave range, and an active "switch" that operates on the basis of the Josephson junction, which provides the quantum effect of particles "seeping" through an insulating material. In the device, the input pulse frequencies diverge through the resonator system, like the notes of an orchestra in their parts, and freeze in anticipation," Alexey Matanin, a junior researcher at the cluster, explained to Izvestia.

The recording process begins with the fact that a stream of photons in the form of a microwave pulse is sent to the resonators and distributed between them. At this point, the "key" closes and separates the system from the outside world. In this form, photons can persist for a long time, he said.

Then, at the reading stage, the user gives nanosecond-long signals that open the "key" and the resonators reconnect to the outside world. At the same time, an exact copy of the original pulse is formed at the output — the same stream of microwave photons, but shifted in time.

Where quantum memory will be useful

According to the scientist, in experiments, the storage time of quantum information was 1.51 microseconds, and the characteristic attenuation time of efficiency was 11.44 microseconds, which is the best performance in the world. The development also demonstrated a storage efficiency of 57.5% during the first reading cycle, several times higher than its foreign counterparts: researchers at Stanford University (USA) reached 21%, and Tsinghua University (China) — 12%.

It is important that the proposed principle eliminates losses at the storage stage, the scientist noted. It is also important that only one control line is involved in the circuit. This simplifies its integration with other systems and makes it more easily scalable.

— For a long time, losses during the transmission and storage of microwave photons were an insurmountable barrier. We have developed a new architecture of a quantum memory cell on a chip, which made it possible to circumvent these limitations and minimize the influence of control elements on the storage of quantum information. For the first time, we have experimentally obtained a device whose theoretical efficiency is unlimited and can potentially reach 100%," said Ilya Rodionov, head of the cluster.

It is also important that the proposed scheme is compatible with superconducting qubits. This paves the way for its integration into real quantum processors, he added.

— The development demonstrated record-breaking parameters, which was an achievement in solving one of the most difficult tasks of quantum engineering. Our device can become the very "quantum RAM" that was lacking to accelerate the development of quantum computing and sensors," said Mikhail Gordin, Rector of Moscow State Technical University.

According to the developers, the use of quantum memory devices will facilitate the implementation of advanced error correction algorithms, which will significantly increase the accuracy of quantum computing. The implementation of the proposed approaches will also make it possible to create distributed quantum systems by increasing the connectivity of qubits.

The development will also be in demand when creating ultra-precise detectors, including quantum sensors and radars. Unlike classical systems, they will be able to register objects with a minimal reflective surface, such as stealth drones.

How to see life on exoplanets

— Quantum memory is an important component of future technologies. These elements, in particular, will ensure the storage and synchronization of information between operations. In quantum communications, they will significantly increase the distance between communication nodes," Maxim Smirnov, an employee of the Kazan Quantum Center, associate professor at the Kazan National Research Technical University named after A.N. Tupolev — KAI, told Izvestia.

Natalia Maleeva, Director of the NUST MISIS Quantum Design Center, noted that the implementation of the resonator system idea is also interesting for quantum sensors. At the same time, when it comes to recording and storing information, the natural requirement is a minimum distortion of the stored information.

— The use of technology in radar looks intriguing. The signal reflected from an aircraft sharpened by stel technology is negligible. The radar does not "see" it, taking it for background noise. The development will allow us to accumulate rare quanta of electromagnetic radiation until there is enough information to confidently identify objects," explained Dmitry Kuzyakin, chief designer of the Center for Integrated Unmanned Solutions.

According to him, this will make modern aircraft camouflage systems useless.

— The advent of quantum storage devices opens up fundamentally new opportunities for air defense systems, intelligence and tactical field complexes. In fact, wherever electronic warfare and detection systems are used, such innovations are in demand," said military expert Dmitry Kornev.

However, a healthy pragmatism should be maintained. Getting things done on paper and prototyping is just the first step. Only after a series of tests in real conditions with interference will it be possible to confirm the technology's transition from the category of advanced research to the category of a serial defense order, he added.

— Based on the development in the future, it is possible to create quantum telescopes that will capture and accumulate individual photons from distant space objects. You can make as many similar devices as you want. Thus, scientists — in theory — will receive a "lens" of almost unlimited diameter and angular resolution, — says Vladimir Afanasyev, an astrophysicist and popularizer of science.

In particular, such systems will make it possible to examine the surface of exoplanets at a distance of 10-20 light-years from Earth, he suggested. If, for example, clouds get into the "lens", this will suggest the possibility of life on the object.

The research results are published in Physical Review Letters, the world's leading physics journal.