In 2009, the Great Wall of China was struck by lasers in the hills of North Beijing. This wasn’t a Star Wars remake or any other sci-fi spin off taking place, but a team of physicists from the University of Science and Technology of China (USTC) attempting to bring science fiction into reality.
From the base location of USTC, lasers were aimed at a detector placed on a rooftop 16 kilometers away. Using quantum properties of the laser’s photons, information was “teleported” across space.
That was seven years ago, and it marked the world distance record for quantum teleportation. However, this was only the beginning for the ambitious team of Chinese physicists.
The achievement was a major step towards ultimately transferring information via photons to a satellite in space—creating the largest quantum information network in the world.
Successfully beaming that information over the Great Wall helped establish the foundational knowledge to create a quantum internet that uses subatomic physics to build a global communication network that many deem “unhackable.” With this knowledge, China is launching the world’s first satellite specialized for quantum-science experimentation in 2016.
The move represents a global statement for China. It signifies the country as a powerhouse in the most advanced quantum sciences and technologies and places them ahead of both Europe and North America in this respect. It is also a new platform for quantum experimentation and its ability to fit together with the general theory of relativity—finally pitting Einstein’s theory of space, time, and gravity against quantum theory.
The Man Behind the Quantum Feat
The man behind the quantum mission is physicist, Jian-Wei Pan. This year is proving to be a culmination in Pan’s long, competitive journey to place this satellite into space.
In 2001, he established China’s first lab for manipulating quantum properties of photons. It was during that time that he began envisioning the concept of quantum satellite communication from space. At age 41, he was the youngest to be inducted into the Chinese Academy of Sciences.
“He almost single-handedly pushed this project through and put China on the quantum map,” said Yu-Ao Chen, a physicist on the team at the USTC, in an interview with nature.com.
Pan’s passion for manipulating quantum properties dates back to the late 1980s in his years of undergraduate study at the USTC. The fascination grew from learning about the paradoxes existing in the atomic realm. It’s the understanding that these elements change when observed that enticed him into a lifelong study in the field.
“I was obsessed with these quantum paradoxes,” said Pan in an interview. “They distracted me so much that I couldn’t even study other things.” He wanted to test the veracity of these almost inconceivable claims, but he could not find a suitable experimental quantum physics lab in China.
Even more perplexing is the quantum property of entanglement, where two or more particles are involved. Both the paradoxes and the entanglement will serve Pan great use in his mission to pioneer a quantum space satellite.
However, most Chinese physicists bursting with intellect and ideas are sent to study in the United States. Pan was adamant about pursuing his scholarly journey in the field but maintained that his big ideas would be brought to his home country of China.
He set out to mentor under the tutelage of a world-leading quantum experimental master Anton Zeilinger, a physicist at the University of Vienna. Zeilinger became Pan’s PhD adviser and then fierce competitor in the quantum-teleportation race in the atmosphere. Now, after seven years of rivalry, the two are collaborators on the satellite launch.
Quantum Paradoxes & Entanglement
To even be impressed by the idea of a quantum-teleportation satellite, one must at least gain a sweeping overview of the physics behind the achievement.
Surendra P. Singh, Professor of Quantum Optics at the University of Arkansa, sat down with BTR to simplify both the details of quantum theory and his ideas on the challenging feat of creating the largest quantum communication network.
Singh explained that the big ideas that allow for this system to work involve both quantum paradoxes and entanglement theory.
“It relies on properties in a system that can exists in multiple states, multiple quant-machanical states,” says Singh. “The idea behind using this superposition of quantum states is that one can transmit communication securely, but it’s not unhackable.”
Subatomic particles, or quantum objects, can exist in many different states of positioning. For instance, a particle can spin clockwise and counterclockwise at same time, or simultaneously be near you as well as all the way across the room. Mathematically this is discovered by measuring the particle’s wave, however when the properties itself are measured, the wave function collapses into a single location. This creates a paradox in understanding the multiple superpositions of quantum objects as measurement proves fallible.
Entanglement strangeness arrives when two or more particles are involved and calculating one particle correlates with the others, even if they are huge distances apart.
The large quantum network will likely have the practical implication of transferring classified information between countries with what is known as a “secret key.”
“When you make a measurement on the quantum system, all of the possible outcomes that existed before that made correlations are destroyed,” points out Singh. This means that the communication network is hackable, but it is made clear to the operators if it has been infiltrated.
As Pan was learning under the master Zeilinger, physicists began supporting the ideas that quantum features such as the ones mentioned above could be used to harness incredible power for quantum computers. Creating quantum security systems were also being tested, since the measurement of quantum particles would inevitably disrupt any encryption code build upon it.
According to Singh, it doesn’t even have to be someone purposefully disturbing the connection, it could simply occur from variables that exist between larger and larger distances.
The Chinese Academy of Sciences and the National Natural Science Foundation of China became enthused with the idea of a secret key in quantum-based technologies and began funding such projects.
The timing was perfect for Pan to begin his mission for the ultimate quantum information network.
Quantum Teleportation and Its impact
The idea of quantum teleportation was not a new phenomenon. In 1993, computer scientist Charles Bennet from IBM in New York and his colleagues coined the term quantum teleportation. They created a system where all information on a quantum object could be scanned in one location and then reconfigured in an entirely new space somewhere else.
The instrumental factor that allows for this is entanglement. Anything you do to one entangled particle will affect another no matter the distance in between. Therefore, the two objects can be manipulated to act like receiving ends of a telephone line—one receiving end gaining the same information as the other end.
However, the greater the distance between, the greater potential for disruptive interactions that could occur between the quantum connection. Currently, quantum particles are transported via optical fibers. These fibers absorb light and keep the entangled photons from traveling more than a pre-set distance.
The theory behind Pan and his team’s work is that the only way to have quantum information beyond the range of a city, it needs to be teleported via satellite.
But could these entangled particles really survive a likely turbulent trip through Earth’s atmosphere and into the vast expanse of outer space?
Here’s where the lasers come in. In 2005, Pan and his team carried out tests across growing distances—from the Great Wall of China back to their university building. They built target detectors that picked out photons teleporting from the background light of lasers and focused their beam directly onto the detectors.
The success of the teleportation across ever increasing distances was proof enough to allow Pan to launch the space satellite in 2016. Thrilled at the success and triumph over the lackluster progress of other nations, Pan still wants other country’s governments to get involved.
Pan invited his mentor and rival Zeilinger to develop a joint goal to secure quantum key communication between Beijing and Vienna.
Currently both Pan and Zeilinger are working together with their teams to analyze the series of tests between the two cities and discuss their findings in workshops at the Perimeter Institute for Theoretical Physics in Waterloo, Canada.
In response to why America has yet to jump on the quantum bandwagon, Singh makes clear that it is not in our scientific priorities and doesn’t consider it a “lose” by any means.
“Certainly I would have liked to see this undertaken by the U.S.,” admits Singh. “In the case with China, they are an emerging economy and want to establish a footprint in the scientific domain—I don’t think anyone doubts the predominance of U.S. science though.”
Singh doesn’t believe this will be changing everyday communication any time soon; this is work specifically for higher levels of encrypted government communication for the most part. He does see it as an exciting obstacle in pushing the limitations of human ideas and capabilities.
“It’s challenging, but that’s what the science enterprises are about. In fact, that’s what human enterprise is about: overcoming challenges,” praises Singh.