- A new Chinese experiment shows that quantum teleportation works between the ground and space. The experiment was performed using a quantum research satellite called Micius, which China launched in 2016. It worked at a distance of 870 miles (1,400 kilometers), many times as far as the previous teleportation record. A quantum physicist says the experiment is “profound” in that it could help lead to supersecure, superfast quantum internet.
In early July, scientists in China revealed they had used a “spooky” property of the universe to pull off teleportation between the ground and space for the first time.
No people or things were teleported, only properties of photons – or particles of light – using a physics theory called quantum mechanics. The experiment was a proof of concept.
But that should not undercut the feat’s importance: This quantum-teleportation experiment worked at distances of up to 870 miles (1,400 kilometers), about eight times as far the previous record. What’s more, according to at least one researcher, the ability to teleport to satellites represents a huge leap toward developing technologies that could reshape the modern world.
J.C. Séamus Davis, a physicist at Cornell University who studies quantum mechanics, said the latest study was “profound” because it demonstrated the basis of a fully “quantum internet” – a technology likely to make our world wide web obsolete.
“Such an internet would be both vastly more powerful, in terms of speed, and vastly more secure, in terms of inability to access private information,” Davis told Business Insider. “There’s no way for eavesdropping to occur without knowing that it’s happened.”
Thirty-two researchers from academic institutions around China posted a draft of the latest study on July 4 to Arxiv, a preprint server for science papers. While scientists haven’t yet peer-reviewed the new study, it follows a related study, published June 15 in the journal Science, that used the same quantum-teleportation satellite, called Micius.
Davis couldn’t say when a quantum internet would go online or what its exact consequences might be. But he believes the impact will be huge, though its development may resemble the inception of the internet in the 1980s.
That moment was initially marked by curiosity and, in some cases, ambivalence. However, the birth of the web led to a decadeslong period of extreme disruption and innovation, and the reshaping of the modern world. A public and fully quantum internet could trigger something similar.
“Quantum physicists can see it coming: the quantum internet, quantum information technology, quantum computing, quantum cryptography,” said Davis, who wasn’t involved in the study. “These are just now coming over the horizon, and in 30 to 50 years from now, they’re going to dominate the way the world works. That’s why I find this paper so striking.”
Harnessing the spookiness of quantum teleportation
Researchers proved in 1992 that teleportation works, at least mathematically, then demonstrated it in the lab for the first time in 1998 using photons. Scientists around the world have replicated and built upon that work ever since.
Quantum teleportation isn’t like the “Star Trek” version of teleportation, where a person is scanned and reassembled somewhere else in the universe. Instead, it involves “entangling” two tiny particles, separating them, and keeping them stable enough to remain linked together.
Entangling binds certain states of particles, like spin or polarization, but traps knowledge of those states in a murky and bizarre situation called “superposition.” When entangled, a particle’s state is considered to be, for example, up, down, or both.
“It’s a weird situation – as weird as if you could have an alive cat and a dead cat at the same time,” Davis said.
Yet when one of the particles is directly measured (or jostled a bit too hard), its state becomes known, and the other particle instantly shows the opposite state. It’s as if the two particles are the same particle, in the same spot and at the same time, no matter how far they’re separated – they somehow “teleport” their hidden states faster than the speed of light.
Albert Einstein called the effect “spooky action at a distance,” mainly to suggest that he thought the idea absurd.
“Einstein couldn’t accept this,” Davis said. “He essentially went to his grave not accepting this as fact, but it’s now been shown millions of times to work.”
How and why photons, atoms, and other particles can be entangled and quantum-teleport their states to one another makes no sense in the context of our everyday lives. At tiny scales, the universe appears to play by different rules, many of which are paradoxical and defy reason. In some quantum-mechanical scenarios, for instance, an effect doesn’t always follow a cause; the effect can, in fact, happen before its cause occurs. (“I didn’t make this up,” Davis said.)
Davis added that no one could be blamed for being confused by quantum mechanics, since “we didn’t evolve to understand” the theory and its counterintuitive ramifications.
“But the math, the predictions starting in the 1920s, have all turned out to be correct,” he said. “It’s the most successful scientific theory in the human race.”
In all those decades of math and experiments, however, no one has ever achieved teleportation from the ground into orbit – until now, anyway. And Davis suspects it’s a game-changer.
Why and how to teleport into space
The reason anyone would want to teleport into space is that the usual way of separating entangled photons, using fiber-optic cables – which the internet partly relies on – is problematic.
Laying fiber-optic cables is expensive and takes a long time. The longer a cable is, the lossier it gets and the more likely it is that entanglement will be destroyed. Even beaming entangled photons through the air by laser doesn’t work after a certain distance; atmospheric disturbances jostle and ruin entanglement.
“A promising solution to this problem is exploiting a satellite platform and space-based link,” since space is mostly empty and less likely to mess with entanglement, the authors wrote. “This work establishes the first ground-to-satellite up-link for faithful and ultra-long-distance quantum teleportation, an essential step toward global-scale quantum internet.”
To pull it off, the researchers used a special transmitter called Ngari, which sits on a Tibetan mountain range. The high altitude put as little air as possible between the transmitter and Micius, which was launched in 2016 and is equipped with a very sensitive photon detector. This vastly improved the chances entangled photons would make it to space intact.
To entangle photons, researchers beamed an ultraviolet laser through a special crystal, which created pairs of photons with opposite – yet unknown – states of polarization. (Polarization is the same property of light that polarized sunglasses can filter out to improve contrast.) In doing so, they created objects called qubits, or quantum-entangled bits.
Mirrors then split up the laser beam and its pairs of quantum-entangled photons. The experiment kept one photon on the ground and sent the other to Micius at a rate of about 4,080 entangled photons per second.
To ensure the satellite was detecting entangled photons at the right times, and to keep the transmitter’s signal strong, engineers took all sorts of precautions.
Micius, for example, carefully blocked light from the moon, tracked stars to know its precise position in orbit, operated at a very cold temperature – since warm objects emit infrared light – and passed overhead at the exact same time every night. Precise timers also helped sync up the devices so they could predict when each photon that left the transmitter would reach the satellite.
The satellite was in view of the transmitter from as far as 870 miles, when it was on the horizon, and as close as 310 miles, when it flew directly overhead.
Over 32 evenings, 911 photon pairs showed teleportation when the scientists measured their states. That may not sound like a lot, especially out of millions and millions of pairs, but it’s a breakthrough.
“It is straightforward to check that one would have to wait for 380 billion years (20 times the universe’s lifetime) to witness one event” with a similar setup through a fiber-optic cable, the authors wrote.
The work that remains
What is not straightforward is getting a public quantum internet up and running.
Although a few small-scale quantum internets have been built, they use fiber-optic cables (not satellites), are small-scale, and generally make compromises for speed and security to interface with traditional computers.
To make a global quantum internet work, China or some other entity would have to figure out how to improve the fidelity of its quantum-internet signals. Likewise, we would need affordable, reliable, and ultimately useful commercial quantum computers and quantum routers to take full advantage of a quantum internet’s speed and security.
On the security side, someone would need to show that strings of many qubits could be reliably sent to and from space to form “quantum keys.” Doing so would blow away all other forms of encryption, since they’d be randomly generated by nature – and thus unbreakable. (Any attempt to listen in on quantum-encrypted data would collapse an entangled pair’s state and produce revealing errors.)
Davis thinks that this moment, when all these technologies jell, is still many years away. But if it happened, he said, we could all reap an unknowable number of new benefits – aside from improving those of our global, public internet.
“Take what we do now and say we’re just going to do it better,” he said. “Your laptop works faster. Your Netflix season downloads in 10 seconds instead of 10 hours. Your medical records are complete and present and secure in any medical system in the world.”
And – of critical importance – “airlines could sell the correct number of seats every flight,” he said.