China’s achievement with quantum satellite challenges reporters
Jian-Wei Pan (left) and Anton Zeilinger prepare for the launch of the Micius satellite last year.
University of Vienna
The word coopetition, oxymoronically yoking cooperation with competition, presents a social paradox as exploitable. Quantum-entanglement experiments, spookily yoking separated photons, present a physics paradox as exploitable. The latest such investigation, announced by Chinese scientists in a US publication, illustrates coopetition’s routineness in science—even though much of the media coverage emphasizes the competition over the cooperation.
The editors of that US publication, Science, summarized the news:
Quantum entanglement has moved out of this world and into space. In a study that shows China’s growing mastery of both the quantum world and space science, a team of physicists reports that it sent eerily intertwined quantum particles from a satellite to ground stations separated by 1200 kilometers. Quantum physics says the quantum states of entangled objects remain linked until one of them is measured. That measurement instantly determines the quantum state of the other, no matter how far away—the “spooky action” at a distance that Albert Einstein was suspicious of. Results from China’s Micius satellite show that the effect is real at a record distance, and the achievement foreshadows other quantum experiments in space.
In the same 16 June issue of Science, Jian-Wei Pan and that team of physicists began their paper with an abstract offering more technical detail:
Long-distance entanglement distribution is essential for both foundational tests of quantum physics and scalable quantum networks. Owing to channel loss, however, the previously achieved distance was limited to ~100 kilometers. Here we demonstrate satellite-based distribution of entangled photon pairs to two locations separated by 1203 kilometers on Earth, through two satellite-to-ground downlinks with a summed length varying from 1600 to 2400 kilometers. We observed a survival of two-photon entanglement and a violation of Bell inequality by 2.37 ± 0.09 under strict Einstein locality conditions. The obtained effective link efficiency is orders of magnitude higher than that of the direct bidirectional transmission of the two photons through telecommunication fibers.
(Physics Today Online posted a somewhat longer summary at a similar technical level.)
Pan, from the University of Science and Technology in Hefei and the youngest researcher ever inducted into the Chinese Academy of Sciences, heads China’s $100 million Quantum Experiments at Space Scale (QUESS) program. He told the Guardian that a quantum network, with security unconditionally ensured by physical law, would benefit all humanity. He says the Galileo Jupiter probe and Kepler space observatory inspired the naming of the quantum satellite for China’s own Micius, who conducted optical experiments in ancient times. Space.com quoted Pan’s hope that “this will promote and boost confidence in Chinese culture.”
For that promoting, China’s government media agency Xinhua exulted over the achievement, thereby emphasizing the competition dimension. Playing on the word entanglement, the agency explicitly linked one of the experiment’s ground stations, Delingha, with the US capital, Washington, DC. Xinhua proclaimed the Chinese team “clearly demonstrated their world leadership,” such that “many world-renowned media have swarmed to report” this news from the “quantum space race.”
“Definitely,” predicted satellite team member Chaoyang Lu to Nature last year, “I think there will be a race.” This year at Australia’s news.com.au, a subhead citing “a new kind of space race” appeared above an article declaring China now “well ahead of the pack.” Jacob Koshy, deputy science editor at The Hindu—a century and a half old and printed in 17 places in India—went so far as to see China’s experiment underlining erosion of Western science dominance. At the Washington Post, the opinion piece “China’s on track to surpass our investment in science” fretted that US science is stagnating.
Some of the “race” framing involves military implications, as seen in a Reuters piece posted online at the New York Times (which bizarrely categorized it with sports). The Wall Street Journal linked China’s motivation to what was learned from Edward Snowden’s 2013 disclosures about “the degree of sophisticated threat Chinese counterespionage and cyberdefenses were facing.” Scientific American suggested that the US might be succeeding but purposefully silent concerning free-space satellites and quantum key distribution. Nature commented similarly.
Scientific American too used “race” framing, but went deeper , engaging the coopetition. It reported that important antecedents of China’s achievement go back two decades, to when Anton Zeilinger of the University of Innsbruck, Austria (he’s currently at the University of Vienna), was Pan’s PhD adviser. Later the two would “compete fiercely” in ground-based photon-entanglement research. Still later they resumed collaborating. The Austrian Academy of Sciences, a QUESS partner, has plans for using Micius to conduct an intercontinental quantum key distribution experiment between ground stations in Vienna and Beijing.
Nature five years ago portrayed Pan and Zeilinger as “fierce rivals” in a “quantum space race,” but also reported their long friendship. The two were planning “the first intercontinental quantum-secured network, connecting Asia to Europe.” The article quoted Pan: “There’s an old Chinese saying, ‘He who teaches me for one day is my father for life.’ In scientific research, Zeilinger and I collaborate equally, but emotionally I always regard him as my respected elder.”
That article also looked forward to “tantalizing” research beyond the physics of a quantum network. There could be tests of quantum theory’s foundations in relation to the general theory of relativity, Nature explained:
Quantum theory and general relativity present fundamentally different conceptions of space and time, and physicists have struggled to meld them into one unifying framework of quantum gravity. In Einstein’s picture, space-time is perfectly smooth, even when examined at infinitesimal scales. Quantum uncertainty, however, implies that it is impossible to examine space at such small distances. Somewhere along the line either quantum theory or general relativity, if not both, must give way, but it is not yet clear which. The satellite experiments could help by testing whether the rules of quantum theory still apply over scales across which gravity’s pull cannot be ignored.
The article also reported that Pan, Zeilinger, and their teams had been looking at satellite-testable foundational questions generated in workshops at the Perimeter Institute for Theoretical Physics in Waterloo, Canada.
The satellite team’s Science paper ends with this: “The satellite-based technology that we developed opens up a new avenue to both practical quantum communications and fundamental quantum optics experiments at distances previously inaccessible on the ground.” But for the most part, press coverage of China’s achievement has overlooked, or at best only glanced at, the fundamental research potential that Micius represents for all of science. Scientific American did report that such research is in planning at the Canadian Space Agency, the National University of Singapore, the University of Illinois, and the Max Planck Institute for the Science of Light in Germany. The South China Morning Post, an international newspaper in Hong Kong, reported similarly.
Concerning applied-physics cooperation, the Guardian reported that Zeilinger, working with Pan, “hopes to have results to report before the end of the year” on an intercontinental quantum network. Concerning fundamental physics, Nature observed in 2016 that Micius could lead not to shooting for the Moon, but to shooting for the moons. The present work could eventually “allow researchers to combine photons from satellites to make a distributed telescope with an effective aperture the size of Earth—and enormous resolution.” The article quoted University of Illinois physicist Paul Kwiat: “You could not just see planets, but in principle read licence plates on Jupiter’s moons.”
Steven T. Corneliussen is Physics Today‘s media analyst. He has published op-eds in the Washington Post and other newspapers, has written for NASA’s history program, and was a science writer at a particle-accelerator laboratory.