The Downlink interviewed Dr. Jon Dowling on the implications of the quantum communications satellite launched by China last summer. The quantum physicist and renowned professor provides insight into two superpowers’ race for the future of space, and information supremacy.
When the Long March 5 rocket departed from Jinquan Satellite Launch Center in the Gobi Desert on 16 August of last year, and deployed its satellite Micius, the People’s Republic of China took the global edge in the quantum communications race, raising questions about the US’s defense communication priorities.
Dr. Jon Dowling calls the launch of the satellite, intended to be the first of a network that would enable distribution of un-crackable quantum cryptographic keys, the “Chinese Sputnik moment,” and says the US needs to act fast before China goes silent.
“I’ve been beating this drum for the [Department of Department] guys for the last six years, and only now, when the Chinese launch something, do they start listening to me,” he said in a phone interview in December.
Dowling, professor and co-director for Louisiana State University’s Hearne Institute of Theoretical physics, has worked in quantum physics, computing, and optics for years, and is one of the country’s leading experts in the field. He has completed notable projects through NASA’s Jet Propulsion Laboratory, the Intelligence Advanced Research Project Activity (IARPA), and the US Army Aviation and Missile Research, Development and Engineering Center, among others. And in terms of the Micius satellite, there are not many Westerners with the same degree of familiarity with the project.
“I got a personal tour of the satellite assembly room, a view of the ground-based version of the satellite they use for testing, a presentation of what they are doing, and they gave me a very nice brass scale model of the satellite that now sits on my desk,” he told The Downlink in an interview, adding that the leader of the Micius project, Dr. Pan Jian Wei, was an old friend.
Distinct from (but related to) quantum computing, quantum optics networks rely on the properties of quantum physics as expressed in photons, typically using lasers passed through non-linear crystals to achieve put photons in quantum states. Quantum optical networks have much to teach us about the underlying principles of quantum physics.
They are also capable of transmitting an encryption key via photons in a quantum state. This powerful technology can produce an encoding system unique in cryptography, in that third parties attempting to even observe the key’s transmission change it in a manner that’s immediately detectable to the encrypted parties, allowing them to discontinue its use. Ground-based quantum communication networks, such as one currently established between Shanghai and Beijing, use fiber optic cables to transmit the photons, but are limited by distance, as the fibers themselves absorb too many of the fragile quantum-state photons and introduce turbulence.
The Beijing-to-Shanghai link overcomes the distance obstacle currently with “nodes” distributed along the route, but at each node the key must be identified and replicated, as opposed to sending the initial photon the entire way. The nodes are then weak points in the link, where traditional hacking could be used to intercept the key. Unlike traditional or “classical”optical signals, which are able to go further with the aid of signal boosters called “repeaters”, there is no such analogous technology for quantum optics.
“There is a design for a quantum repeater, which is essentially a small special-purpose quantum computer, and we don’t have quantum computers just yet, so we don’t have quantum repeaters just yet, either,” said Dowling. “So that’s where the satellite comes in.”
The Micius satellite seeks to bypass limitations of ground links by transmitting quantum-state photons through the atmosphere. While clouds and other atmospheric disturbances can interfere with optics transmissions, only a few miles up, absorption and turbulence drop off exponentially. Sending an optical signal any distance at sea level means going through the maximum density of gases and airborne particles the entire distance, while sending it down from space minimizes that interference, as the signal passes through the least-possible area of absorption and interference.
“So a 10-kilometer link sideways, horizontal between two ground stations, is equivalent of the same amount of air going 200 kilometers straight up,” said Dowling.
The satellite uses two lasers: one that provides an alignment link with a receiver on the ground, the other laser sending the quantum particles to the station after the link is established.
‘Alice’ is on the satellite, ‘Bob’ is on the ground
In the shorthand of encryption, “Alice” and “Bob” refer to two hypothetical parties trying to communicate a secret message, with “Eve” as the hypothetical eavesdropper. Dowling explained that, with the single-photon protocol, Alice sends the photons down and establishes a random binary key to Bob in Shanghai. Then, the satellite moves over Beijing, Alice runs the protocol again, sharing the binary sequence with Beijing, transmitting an identical key. They can then use that to communicate with each other, even over a cell phone or fiber optics line, because the key is what’s being transmitted, not the message.
“‘Alice is on the satellite, Bob is on the ground. So as long as the satellite is a secure platform, there’s an operation [Alice] can do there to ensure that at the end of the procedure, Beijing and Shanghai have an identical key to communicate with,” he said.
Using the satellite to deliver the key allows the two recipients to coordinate their encryption keys — combining quantum physics with classical cryptography. The satellite may also prove to function at an even more sophisticated level, using entangled pairs of photons to communicate from Micius, 430 miles above, to the station below instantaneously — at a speed faster than light.
Whether the entangled quantum-state photons are robust enough (and local reality non-real and non-local enough; until Micius’s launch, no one has been able to study the effects of entanglement at such a distance) to survive has yet to be seen.
If breaking a code generated by a secure satellite hundreds of miles away from the nearest spy sounds daunting, it is. In fact, it’s beyond daunting: if anyone tries to listen in, the laws of quantum physics kick in. The act of observing of particles in a quantum state profoundly changes that state. Any party attempting to eavesdrop alert the encrypted parties that the key has been compromised, and should no longer be used.
“This is called the ‘no-cloning theorem,’” said Dowling. “People are more familiar with Heisenberg’s Uncertainty Principle. If Eve tries to measure the state of the photons, she irreversibly changes them, and that can be detected by Alice and Bob, so they know their key is unusable, because it’s been attacked.”
As a large number of photons (in both the single and entangled-pairs protocols) will be lost to atmospheric turbulence, Eve could in theory (and with the right technology) siphon off a small number of these encrypted photons without Alice and Bob noticing.
“The standard thought is that the eavesdropper would measure some small fraction of the photons, because not all the photons make it through; some are lost to absorption in the atmosphere, or in the fiber; so there’s always some level of that,” said Dowling. “So the ideal thing would be for Eve to hide in the noise floor, where she just siphons off a few photons, but not so much to make herself visible.”
The technique is called “photon splitting,” but countermeasures already exist.
“Every once in a while, instead of sending a single photon, they could send a bright classical pulse, which Eve doesn’t know is coming, and the small amount she’s hiding in becomes a large amount and now she’s visible…like a floodlight. It’s called ‘decoy pulses.’
“So, if she’s siphoning away 1% of single photons, she’s not visible, but the decoy pulse might contain 1020 of photons, and 1% of those is a lot, and they’ll see her.”
Separate systems, separate policies
The US maintained a dedicated research-and-development strategy for quantum optics from around 2006 until 2010, when the door shut on quantum optics in favor of semi- and super-conducting quantum computers. Dowling said his program, funded by IARPA, was one of those cut.
“From about 2006 to 2008 there was a fairly large quantum computing maturation concept. It was a four-year program, $1.5 million per year, to develop a scalable, all-optical quantum computer. It was funded by the U.S. intelligence agencies. That program did not have in its statement of scope of work any of the quantum communications stuff — however, many of the gizmos you make for an optical quantum computer are the same gizmos you make for an optical communications network.
He said that, at the end of the four-year project, his team submitted for renewal but they were told there would be no further funding.
“So some people in the US government made a decision to not continue the optical quantum computer research, which inadvertently short-circuited the optical quantum network, because they were one and the same thing,” he explained.
Dowling speculated that the decision was made because the optical quantum computer was considered less scalable. Regardless, the sophistication of the project mandated a relatively large budget – one unlikely to be replaced through other venues.
“Cutting off the funding for the quantum optical computer inadvertently cut off funding for the optical quantum network and nobody else could touch it at the same level of funding,” said Dowling. “Like [the National Science Foundation] – you don’t get $1.5 million a year from the NSF. “You get a $150,000 if you’re lucky.
“So this volcano of optical quantum information processing collapsed, in 2010, into an atoll with just a little bit of peripheral stuff from some of the low-order defense agencies and the NSF,” he continued. “But nobody went in to rebuild that mountain, and that collapse put us behind six years to now.”
And Dowling doesn’t believe there was a “secret plan” for a quantum satellite somewhere else.
“Everyone says, well, the US must have a classified program,” said Dowling. “If they do, they’re hiding it really well. The only program I know of was in Los Alamos [New Mexico]. Parts of it were classified, but it was shut down a few years ago. Their budget was cut to zero by IARPA.”
Whatever the reasoning behind the decision to drop the program, Dowling said doing so put us years behind the Chinese, who approached quantum from a markedly different angle.
While the US focused on building a quantum computer capable of breaking classical encryption techniques, the Chinese are attempting to leave the world of classical encryption altogether. Although a quantum computer with sufficient quantum memory (a technology that has eluded scientists to this point) could be used to break even the most sophisticated codes, it can’t be used to hack quantum cryptography – in fact, nothing can.
“It’s immune to an attack by even a quantum computer,” said Dowling. “It’s unbreakable by any means, actually; that’s been proven mathematically.”
So, why did the US cut funding to a program developing an unbreakable quantum encoder? Perhaps because they didn’t truly realize they were developing one.
“Most of this was driven by the Department of defense and the intelligence agencies, and for whatever reason they became enthralled with this quantum codebreaker, the quantum computer, and put all of their money into that,” he said. “I think they thought ‘we don’t really need a quantum communications system until the quantum computer is built, and we haven’t built that first’ — because the quantum computer will break the old post-key encryption systems, the classical ones. But the Chinese took the reverse logic.”
The effects could be profound. The United States relies on a variety of human and signals intelligence coming from the People’s Republic to make broad, strategy-level decisions, as well as narrower tactical policy. The Chinese plan to have a network of quantum-encryption satellites orbiting the globe by 2030, a fleet of spy-proof communications platforms.
They also see the satellites, and space in general, as essential to the China-centric future they’re working toward. In fact, the satellite’s name, Micius, is a Latinized spelling of Mohi, the ancient Chinese philosopher known for both moral austerity and military engineering. Mohi designed the “cloud ladders” that enable armies to breach walled fortifications.
Indeed, in the parlance of the People’s Liberation Army, “zhi tian quan” (the domination of space) is a critical step toward “zhi xinxi quan” (the domination of information). From a strategic perspective, the two are inseparably linked.
“Here’s the real concern. The NSA, as you know, regularly tap encrypted information from other countries. They have banks of supercomputers, the biggest super computer farms in the world, where they crack these secret codes, public key encryptions,” said Dowling. “If China rolls out an entire quantum encryption system, the NSA classical attacks will be useless, and their entire country will go black: we won’t be able to see anything that they’re doing, either financially or militarily, and that could happen within ten years. That’s pretty scary, that we would no longer have any information intelligence coming out of Chinese communications whatsoever. I would be worried, if I was the new administration.”
The race to quantum superiority
Dowling also noted that, in terms of quantum information processing, China isn’t the US’s only problem. While no one yet has a functioning universal quantum computer, many private companies are on the verge of major breakthroughs. Big announcements in quantum computing from Google, Microsoft, IBM, and D-wave, which recently released an open source version of its basic quantum-computing software to developers, indicate that any one of them could have a fully functioning universal quantum computer in the next few years.
The implications are serious, and not constrained to military codebreakers. Nearly all secure information systems rely on public key encryption, from the financial sector to systems shielding electronic healthcare records – and a quantum computer in the wrong hands could be a powerful destabilizing force.
“Ten years ago, they thought [the quantum computer] was fifty years off, and now it might be five or ten. So that’s scaring them, too, as that’s the entire crypto system,” Dowling said.
Even so, Dowling is convinced that, with the proper motivation, the U.S. can rebound – if they move fast.
“Part of my goal talking to you is to get this to the front of everyone’s mind,” he said. “We need to react, and I think making this known widely to the public is important, that the US program is behind in all of this.
Although Dowling thinks that, in the end, cooperation between the U.S. and China would be ideal, he believes the U.S. has every reason to play catch-up.
“I wrote in my book [‘Schrödinger’s Killer App’], ‘the future quantum Internet will have China stamped all over it.’ I wrote that in the fall of 2012, so a little over four years ago. And nobody listened to me. I sent threat assessments, I went to conferences, I beat on the table and…‘what are the Chinese doing?’… now I’m going to a two-day conference in the Washington area where all those talks are classified except mine. So I can’t attend any of these talks. And you can bet that’s what they want to hear about. Now they’re listening to me.”
He said that catching up was possible based on examples of US history, referencing the Manhattan Project, which saw the production of the A-bomb in around two years. Dowling believes that an effort on that order is required, but noted the US doesn’t linger behind in space for long.
“You know it’s interesting, if you think about Sputnik. The first man in space was Yuri Gagarin, and Sputnik was a Russian thing, but once we geared up, the US were the first to land on the moon. So the US has the propensity to move quickly when they see there’s a need. There’s another example in the Manhattan Project, right? Never underestimate the US’s ability to play catch-up and then trounce the competition, I think,” he said.
“But it’s going to take something like a Manhattan project in quantum networks to do it,” he added.