Research team takes fundamental step toward working quantum internet

Research into quantum computing and quantum networks is underway around the world in hopes of developing a quantum internet in the future. A quantum internet would be a network of quantum computers, sensors and communication devices that create, process and transmit quantum states and entanglements. It is expected to improve the company’s Internet system and provide some services and security that the current Internet does not have.

A team of Stony Brook University physicists and their collaborators have taken an important step toward building a quantum Internet testbed by demonstrating a fundamental quantum network measurement using room-temperature quantum memories. Their findings are described in an article published in npj Quantum information.

The field of quantum information essentially combines aspects of physics, mathematics, and classical computing to use quantum mechanics to solve complex problems much faster than classical computing and to transmit information in impossible ways. to hack.

As the vision of a quantum Internet system grows and this area sees renewed interest from researchers and the general public, accompanied by a large increase in invested capital, a true prototype of a quantum Internet n was not built.

According to the Stony Brook research team, the main obstacle to realizing the potential to make communications networks more secure, measurement systems more precise, and algorithms for certain scientific analyzes more powerful, lies in the development of systems capable to transmit quantum information and entanglement across many nodes. and over long distances. These systems are called quantum repeaters and constitute one of the most complex challenges in current physics research.

Researchers have advanced the capabilities of quantum repeaters in their latest experiments. They built and characterized quantum memories operating at room temperature and demonstrated that these memories had identical performance, an essential characteristic when it comes to building large-scale quantum repeater arrays that will include several of these memories.

They tested the identity of these memories in their functionality by sending identical quantum states into each of the memories and performing a process called Hong-Ou-Mandel interference on the memory outputs, a standard test for quantifying the indistinguishability of the memories. properties of photons.

They demonstrated that the process of storing and retrieving optical qubits in their room-temperature quantum memories does not significantly distort the joint interference process and enables memory-assisted entanglement exchange, a protocol for distributing the entanglement over long distances and the key to building an operational quantum system. repeaters.

“We believe this is an extraordinary step toward developing viable quantum repeaters and the quantum Internet,” says lead author Eden Figueroa, Ph.D., Presidential Professor of Innovation at Stony Brook and director of the Center for Distributed Quantum Processing, which holds a joint appointment at the U.S. Department of Energy’s Brookhaven National Laboratory.

Additionally, the quantum hardware developed by the team operates at room temperature, which significantly reduces operating costs and makes the system much faster. Much quantum research takes place not at room temperature, but at temperatures near absolute zero, which are more expensive, slower and technically more difficult to network. Thus, room temperature technology is promising for building large-scale quantum networks.

The team not only achieved results in quantum memory and room temperature communication, but also patented their approach. They received US patents relating to room temperature quantum storage and high repetition rate quantum repeaters.

“Having these fleets of quantum memories work together at a quantum level and at room temperature is something essential for any quantum Internet, at any scale. To our knowledge, this feat has never been demonstrated before, and “We hope to build on this research,” Figueroa points out, noting that their patented technology allows them to further test the quantum network.

Co-authors Sonali Gera, a postdoctoral researcher, and Chase Wallace, a doctoral student, both in the Department of Physics and Astronomy, worked closely with Figueroa, along with other colleagues, during the experiment, which, in in a sense, aims to effectively “amplify” the entanglement over distances, the essential function of a quantum repeater.

“As the memories are capable of storing photons with a user-defined storage duration, we were also able to show the temporal synchronization of photon retrieval despite the photons arriving in the memories at random times, which Another feature that is necessary for a quantum repeater system to work is another feature,” Gera explains.

She and Wallace add that some of the next steps in the team’s research include building and characterizing sources of entanglement compatible with quantum memories and designing mechanisms to “announce” the presence of photons stored in many quantum memories .