In a joint effort by Yale University, Stony Brook University, and Brookhaven National Laboratory, scientists have been working on a project using free-space optics to transmit quantum signals through the air using lasers. The specific project is called Q-LATS for Quantum Laser Across the Sound, where signals are being transmitted 27 miles from a tower at Yale across Long Island Sound to a tower at Stony Brook University.

Quantum computers are used to create qubits, which have the ability to exist as both a one and a zero simultaneously. This allows a quantum computer to explore multiple scenarios at the same time. Qubits can be created using trapped ions or photons. Quantum communications function by generating entangled photon pairs. One photon is retained and used for calculations, while the other is sent to a distance location. Anything done with the retained photon is sensed at the distant end, thus transmitting the details of the computations.

The project is looking for alternatives to using fiber cables. It turns out to be very challenging to transmit quantum signals through fiber since some of the qubits are lost during the transmission. Fiber cables used to transmit quantum signals work best when heavily shielded and buried, making it costly to establish paths for future quantum communications.

The Q-LATS project hopes to show a reasonable alternate to fiber in places where costly fiber routes are impractical, such as across the Sound. Free-space optics can be used to transmit quantum signals in urban locations, across water, and even into space.

Transmitting light signals through the air has limitations due to rain, fog, and atmospheric turbulence, but the scientists believe these shortcomings can be more easily overcome than finding the funding to build specialty fiber routes.

For now, quantum transmissions are mostly of interest in academia to transmit signals between universities. But quantum computing holds some interesting properties that should eventually make it of use for data centers, large businesses, the military, and others. Quantum signals are seemingly nearly impossible to intercept or hack because the effort to do so instantly interferes with the transmission of qubits. That’s even more so with free-space optics, where a hacker would have to somehow intercept a line-of-sight transmission through the air.

Quantum communications might eventually become the standard for sending highly confidential or sensitive information. It’s not hard to imagine using free-space lasers to transmit quantum signals between Wall Street firms, between large businesses and data centers, and between government and military locations that require a secure path.