Researchers Propose Vacuum Tube Quantum Network Across Country

Researchers at the University of Chicago Pritzker School of Molecular Engineering have proposed a new method to build a quantum network that spans the country, using vacuum beam guides in which qubits can travel thousands of miles inside small vacuum-sealed tubes. This approach could enable fast and secure communication over long distances, a crucial step towards realizing the full benefits of quantum computers. Led by Professor Liang Jiang, the team’s design involves using arrays of spaced-out lenses to focus photons encoding quantum data as they move through the vacuum tubes.

The proposed network would have ranges of thousands of kilometers and capacities of 10 trillion qubits per second, surpassing any existing quantum communication approach. Collaborating with scientists at Stanford University and the California Institute of Technology, the researchers drew inspiration from the Laser Interferometer Gravitational-Wave Observatory’s use of vacuum tubes to detect gravitational waves. If successful, this technology could be used for secure communication, distributed quantum computing networks, and even new kinds of telescopes and synchronized clocks.

Building a Quantum Network Across the Country

Quantum computers have the potential to revolutionize various fields, including cybersecurity, communications, and data processing. However, to fully harness their power, multiple quantum computers need to be connected to form a quantum network or a quantum internet. Researchers have been struggling to develop practical methods for building such networks, which require the transmission of quantum information over long distances.

A team of researchers at the University of Chicago Pritzker School of Molecular Engineering (PME) has proposed a novel approach to address this challenge. They suggest building long quantum channels using vacuum-sealed tubes with an array of spaced-out lenses. These vacuum beam guides, approximately 20 centimeters in diameter, could have ranges of thousands of kilometers and capacities of 10 trillion qubits per second, surpassing any existing quantum communication approach.

The proposed system would enable photons encoding quantum data to move through the vacuum tubes, remaining focused thanks to the lenses. This innovative method combines the advantages of previous approaches, including fiber-optic cables and satellites, to transmit optical photons that can act as qubits. By using a vacuum environment, the researchers aim to minimize attenuation and maximize the transmission of information.

The Challenges of Quantum Communication

Classical computers rely on conventional bits, represented as 0 or 1, whereas quantum computers utilize qubits, which exhibit quantum phenomena such as superposition and entanglement. These properties enable quantum computers to analyze new types of data and store and pass along information in secure ways. However, connecting multiple quantum computers is crucial to unlock their full potential.

Currently, networks used to connect computers are not ideal for transmitting quantum states because they cannot maintain the quantum properties of qubits. Researchers have explored alternative methods, including using fiber-optic cables and satellites to transmit optical photons. While these approaches have shown promise, they are limited by factors such as photon absorption in fibers and atmospheric interference.

Inspiration from LIGO

The Laser Interferometer Gravitational-Wave Observatory (LIGO) at the California Institute of Technology has successfully built huge ground-based vacuum tubes to detect gravitational waves. The experiments at LIGO have demonstrated that photons can travel thousands of kilometers within a nearly molecule-free vacuum environment.

Inspired by this technology, the researchers at PME began exploring how smaller vacuum tubes could be used to transport photons between quantum computers. Their theoretical work has shown that these tubes, if designed and arranged properly, could carry photons across the country. Moreover, they would only require medium vacuum (10^-4 atmosphere pressure), which is much easier to maintain than the ultra-high vacuum (10^-11 atmosphere pressure) required for LIGO.

Overcoming Technical Challenges

One of the main challenges in implementing this technology is that as a photon moves through a vacuum, it spreads out. To overcome this, the researchers propose placing lenses every few kilometers to focus the beam over long distances without diffraction loss. They are planning tabletop experiments to test the practicality of the idea and then plan to use larger vacuum tubes such as those at LIGO to work on how to align the lenses and stabilize the photon beams over long distances.

Additionally, implementing this technology on a larger scale poses civil engineering challenges that need to be addressed. However, the ultimate benefit is the potential for large quantum networks that can communicate tens of terabytes of data per second.

The proposed vacuum beam guide system has the potential to revolutionize quantum communication and enable the creation of large-scale quantum networks. The researchers’ work is a significant step forward in addressing the challenges of transmitting quantum information over long distances. As they continue to develop and test their idea, it may pave the way for breakthroughs in various fields, from cryptography to materials science.

The funding agencies that supported this research include the Army Research Laboratory, Air Force Research Laboratory, National Science Foundation, NTT Research, Packard Foundation, the Marshall and Arlene Bennett Family Research Program, and the U.S. Department of Energy.