China’s hack-proof quantum satellite leap into space leads the world
Groundbreaking project could result in breakthroughs in cryptography and teleportation
China launched the world’s first quantum science satellite into space early on Tuesday morning, with the project carrying the hopes of scientists around the world.
But its first mission, to establish a hack-proof communication line between China and Europe, will also have major national security implications.
At 1.40am, the small satellite, recently named Micius after an ancient Chinese philosopher and engineer, began a journey into the big unknown on top of a Long March 2D rocket launched from the Jiuquan Satellite Launch Centre in Inner Mongolia’s Gobi Desert.
Eight years ago, quantum physicist Pan Jianwei and space engineer Wang Jianyu teamed up to build the world’s first quantum satellite in the hope of finding the portal to a whole new universe.
“Pan has some big ideas, my job is to squeeze them in a satellite,” Professor Wang, commander in chief of China’s quantum science satellite (QSS) project, told the South China Morning Post in an exclusive interview.
The satellite was initially called QUESS (quantum experiments at space scale) and then QSS. Pan, the project’s chief scientist, said they had been scratching their heads for a long time to find a proper name for it.
Micius was chosen not only because it fit the pioneering nature of the experiments, but also as a nod to Chinese culture, Pan told state media on Monday. More than 2,400 years ago, Micius proposed that light always travelled in a straight line and that the physical world was made up by particles. He also built the world’s first pinhole camera.
The QSS project began at the Shanghai Institute of Technical Physics, a subsidiary of the Chinese Academy of Sciences (CAS), in 2008.
The satellite, weighing less than a Smart car, will be looking for a universe different from Einstein’s. One where a cat can be alive and dead at the same time, where bits of information can be “teleported” from one galaxy to another faster than the speed of light, where the internet cannot be hacked, and where a calculator can run faster than all the world’s super computers combined.
“The QSS missions are something never attempted by other nations,” Wang said. “China has been trailing the footsteps of others for more than a century. QSS will be our first step ahead of others [in space].
“It is a tiny step, but it is a step for the human race.”
In ancient times, China was the land of innovation, inventing black powder, paper, printing and the compass. Now, after decades of rapid economic development, it has built up the world’s largest army of scientists and engineers, some armed with cutting-edge technology and state-of-the-art hardware, and is ready to reclaim the glory of the past with ambitious projects.
Wang said the quantum satellite had three successively more challenging missions, with the first being the establishment of the hack-proof communication line.
A message would encrypted by a unique cryptographic key chain in Beijing and sent to Vienna through the conventional telecommunications network. At the same time, the key chain would be beamed to the quantum satellite by Beijing in the form of photons with various quantum properties such as clockwise or counterclockwise spins, and then the satellite would relay the cryptographic keys to the receiver in Vienna to decipher the message.
Quantum properties – the states of a particle – cannot be measured or cloned without destroying the particle’s original quantum states, so the cryptographic keys, in theory, could not be stolen.
The technology had obvious military value and Micius would have ended up as a secret military satellite if not for a rare fight led by Professor Pan and other Chinese scientists against the generals of the People’s Liberation Army.
“Originally, the army wanted to take over the responsibility [to bring quantum technology to space],” Pan told Nature magazine in January. “We at the CAS really worked hard to convince our government that it is important that we have a way to launch science satellites … it was finally agreed that CAS is the right organisation.”
The Chinese scientists’ efforts won respect and applause from colleagues and competitors in Europe, the United States, Russia, Canada and Japan who had proposed similar plans to take quantum technology into space to their governments only to face delays or postponements for a range of reasons, including budget cuts.
Professor Anton Zeilinger, who was Pan’s mentor when he was a PhD student in Vienna and now leads a quantum satellite project in Europe, said the launch of Micius launch would benefit everyone.
“The quantum satellite will for the first time prove that quantum communication on a worldwide scale is possible,” he said. “This is a crucial step to the future quantum internet.”
But it is the satellite’s second and third missions that reveal the scale of the Chinese scientists’ ambitions and have physicists around the world holding their breath.
One of the most intriguing elements of quantum theory is the entanglement of particles. If two particles are entangled, the change of quantum state on one particle would immediately trigger a counter-change on the other. In theory, the entanglement would occur regardless of the distance between the particles, but the greatest distance of entanglement on the ground, achieved by a team led by Pan and Wang, was only 100km.
Micius will seek to improve on that by an order of magnitude, beaming one entangled photon to a ground station in Delingha, Tibet, and the other to a station in Lijiang in Yunnan or Nanshan in Xinjiang, so see if the entanglement can be maintained between two ground stations more than 1,000km apart.
If the results of the second mission are positive, the satellite’s third mission will take quantum theory to its most exciting application: quantum teleportation in space.
Researchers will generate a pair of entangled photons at a ground station. One photon will be beamed to the satellite, the other kept on the ground. Then, the scientists will alter the quantum state of the particle on the ground, such as giving it a clockwise spin. A detector on the satellite will tell if a counterclockwise spin occurs simultaneously on the particle in space.
Many problems remain to be solved, such as maintaining the entangled state of quantum particles, which is fragile and can be lost in long-distance space flight, but Wang said the first glimpse of hope was on the horizon.
“Before the appearance of television, sending images from one place to another was considered magic,” he said. “Quantum teleportation is magic, but it may become as simple and common as television in the future.”
Wang still has many practical issues to worry about. Though all the technology and equipment has been tested on the ground, there’s no guarantee it will all work in space. In a ground experiment, the equipment can be fine-turned or fixed; once in space, the hardware on the satellite cannot be modified.
But Wang said their biggest challenge was distance. To beam a single photon from the satellite to a one-metre-wide telescope on the ground, or to catch a single photon from the ground with a satellite moving at 7,000km/h to 8,000km/h, with rain, clouds and air turbulence in between, would be “the most difficult sniper shot ever”, he said.
Development of the quantum satellite had taken China’s space technology to new heights in many areas, he said, including ultra-precise tracking, timing and spacecraft control.
But what if the experiments do not find what they are looking for, for instance the particles fail to entangle beyond a certain distance. Wang said it was something he had discussed with Pan.
“If the QSS shows some fundamental laws of quantum physics do not work in the universe, we will be equally thrilled,” he said. “It will open another door to the unknown.”