Vacuum tubes could revolutionize quantum networks

The new approach to quantum networks involves using vacuum tubes with spaced lenses to transmit quantum data via photons over long distances. The method, developed by scientists at the University of California, Los Angeles, University of Chicago Collaborators, aim to enable secure, high-capacity quantum communication across vast distances.

Quantum computers offer powerful ways to improve cybersecurity, communications, and data processing, among other areas. However, to fully reap these benefits, many quantum computers must be connected to create quantum networks or a quantum internet. Scientists have struggled to find practical ways to build such networks, which must transmit quantum information over long distances.

To make the quantum network a reality, researchers from Jiang's group at the Pritzker School of Molecular Engineering at the University of Chicago have proposed building long quantum channels using vacuum tubes sealed with an array of spaced lenses. Credit: Jiang's group

Innovative quantum communications

Researchers at the Pritzker School of Molecular Engineering (PME) at the University of Chicago have proposed a new approach: building long quantum channels using vacuum tubes and a series of spaced lenses. The vacuum beam guides would be about 20 centimeters in diameter, have a range of several thousand kilometers, and a capacity of 10 trillion qubits per second, better than any other approach to quantum communications. The photons of light encoding quantum data would travel through the vacuum tubes and be kept focused by the lenses.

“We think this kind of network is possible and has a lot of potential,” said Liang Jiang, a professor of molecular engineering and lead author of the new work. “It can be used not only for secure communication, but also to create distributed networks. Quantitative statistics “Networks, distributed quantum sensing technologies, new types of telescopes, and synchronized clocks.”

Jiang collaborated with scientists from Stanford University and the California Institute of Technology on the new work, published July 9 in Physical examination messages.

Professor Liang Jiang of the Pritzker School of Molecular Engineering at the University of Chicago tests the proposed quantum network using vacuum beam guides, which would have a range of several thousand kilometers and a capacity of 10 trillion qubits per second, better than any other existing quantum network. Communication approach. Credit: UChicago Pritzker School of Molecular Engineering/John Zich

Quantum Properties and Data Transfer

While classical computers encode data in conventional bits (represented by 0 or 1), quantum computers rely on qubits, which can exhibit quantum phenomena. These phenomena include superposition (a kind of mysterious combination of states) as well as entanglement, which allows two quantum particles to be linked to each other, even over large distances.

These properties give quantum computers the ability to analyze new types of data and store and transmit information in new and secure ways. Connecting multiple quantum computers could make them more powerful, because they could share their data processing capabilities. However, the networks typically used to connect computers are not ideal, because they cannot retain the quantum properties of qubits.

“You can’t send a quantum state over a classical network,” Jiang explains. “You can send data in a classical way, and a quantum computer can process it, but the result is sent back in a classical way.”

Some researchers have tested ways to use fiber-optic cables and satellites to transmit light photons, which can act like qubits. Photons can travel a short distance through existing fiber-optic cables, but they typically lose their information quickly when they are absorbed. Photons that bounce back to satellites and return to Earth in a new location are less absorbed by the vacuum of space, but their transmission is limited by atmospheric absorption and the availability of satellites.

“We wanted to combine the advantages of both of these previous approaches,” says Yuexun Huang, a graduate student at PME and first author of the new study. “In a vacuum, you can send a lot of information without attenuation. But being able to do that on Earth would be ideal.”

“We believe that this type of network is possible and has great potential.”

— Professor Liang Jiang

Terrestrial vacuum tubes and quantum information

Scientists working on the Laser Interferometer Gravitational-Wave Observatory (LIGO) at the California Institute of Technology (Caltech) have built massive ground-based vacuum tubes to carry moving photons of light that can detect Gravitational waves. Experiences in lego He showed that within a vacuum almost devoid of particles, photons can travel thousands of kilometers.

Inspired by this technology, Jiang, Huang, and their colleagues began to sketch out how smaller vacuum tubes could be used to transmit photons between quantum computers. In their new theoretical work, they show that these tubes, if designed and arranged correctly, could transmit photons across the country. What’s more, they would only need a moderate vacuum (10^-4 atmospheres of pressure), which is much easier to maintain than the ultrahigh vacuum (10^-11 atmospheres of pressure) required at LIGO.

The main challenge is that Photon “When you move in a vacuum, the beam spreads out a little,” Jiang explains. “To address this problem, we propose placing lenses every few kilometers that can focus the beam over long distances without losing diffraction.”

Working with researchers at the California Institute of Technology, the group plans to conduct tabletop experiments to test the practicality of the idea, and then plans to use larger vacuum tubes like LIGO to work out how to align lenses and stabilize photon beams over long distances.

“A broader application of this technology poses some civil engineering problems that we also need to solve,” Jiang said. “But the ultimate benefit is that we have large quantum networks capable of transmitting tens of terabytes of data per second.”

Funding: This work was supported by the Army Research Laboratory, Air Force Research Laboratory, the National Science Foundation, NTT Research, the Packard Foundation, the Marshall and Arlene Bennett Family Research Program, and the U.S. Department of Energy.