NASA has introduced the Performance-Enhanced Array for Counting Optical Quanta (PEACOQ) detector. This network system can monitor the precise time each photon hits it, within 100 trillionths of a second, at a pace of 1.5 billion photons per second, similar to measuring individual drops of water while being sprayed by a firehose. This robust communication network will help aid in the long-distance communications of quantum computers.
Quantum computers can be millions of times quicker than traditional computers. Quantum computers, however, will require a separate quantum communications network to communicate across large distances. Thus, to address this limitation and help form the necessary network, scientists at NASA’s Jet Propulsion Laboratory and Caltech created a gadget that can count massive numbers of single photons – quantum particles of light – with extraordinary precision, of which no other detector has come at par with its rate.
The PEACOQ detector, created by JPL’s Microdevices Laboratory and funded by NASA’s Space Communications and Navigation (SCaN) program within the agency’s Space Operations Mission Directorate, must be kept at a cryogenic temperature one degree above absolute zero, or minus 458 degrees Fahrenheit (minus 272 degrees Celsius). This maintains the nanowires’ superconductivity, which is essential to convert absorbed photons into electrical pulses that deliver quantum data.
Credits: NASA/JPL-Caltech
The detector itself is quite small. It comprises 32 niobium nitride superconducting nanowires on a silicon chip, with connectors that fan out like the plumage of the detector’s namesake. Each nanowire is 10,000 times thinner than the thickness of human hair.
“Transmitting quantum information over long distances has, so far, been very limited. A new detector technology like the PEACOQ that can measure single photons with a precision of a fraction of a nanosecond enables sending quantum information at higher rates, farther.”
Ioana Craiciu, PEACOQ project team member, postdoctoral scholar at JPL and lead author of the study
Although the detector must be sensitive enough to detect single photons, it must also be robust enough to endure many photon strikes. As a photon strikes one of the detector’s nanowires, it becomes temporarily unable to detect another photon, a period known as “dead time.” However, each superconducting nanowire is designed to have as little dead time as possible. Furthermore, PEACOQ is outfitted with 32 nanowires, allowing others to pick up the slack when one is “dead.”
“In the near term, PEACOQ will be used in lab experiments to demonstrate quantum communications at higher rates or over greater distances,” said Craiciu. “In the long term, it could provide an answer to the question of how we transmit quantum data around the world.”
Ioana Craiciu, PEACOQ project team member, postdoctoral scholar at JPL and lead author of the study
PEACOQ is designed with high-bandwidth optical communications
PEACOQ is based on the detector created for NASA’s Deep Space Optical Communications (DSOC) technology demonstration and is part of a larger NASA effort to provide free-space optical communications between space and the earth. DSOC will launch later this year as part of NASA’s Psyche mission to demonstrate for the first time how high-bandwidth optical communications between Earth and deep space could work in the future.
“It’s all kind of the same technology with a new category of detector. Whether that photon is encoded with quantum information or whether we want to detect single photons from a laser source in deep space, we’re still counting single photons.”
Matt Shaw, who leads JPL’s superconducting detector work
Accordingly, a dedicated free-space optical quantum network could incorporate space “nodes” aboard satellites circling Earth to allow quantum computers to communicate outside these constraints. These nodes would relay data by creating pairs of entangled photons that would be transferred to two quantum computer terminals on the ground hundreds or perhaps thousands of kilometers distant.
Even when separated by a wide distance, pairs of entangled photons are so intimately coupled that detecting one instantaneously impacts the findings of measuring the other. Nevertheless, for these entangled photons to be received on the ground by a quantum computer’s terminal, an extremely sensitive detector such as PEACOQ is required to accurately measure the moment each photon is detected and transfer the data it carries.
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