AsianScientist (Jul. 19, 2019) – This year marks the 50th anniversary of the first demonstration of information transfer between two computers on ARPAnet, the grandfather of today’s internet. The simple one-word message—LOGIN—communicated on the fledgling ARPAnet may seem rather unremarkable by today’s standards, but it was a technological paradigm that has since transformed the way we communicate.
From e-commerce to the cloud, we can thank the internet for a wide range of innovative technology embedded in our daily lives. Despite its omnipresence, however, the internet still struggles with some key vulnerabilities, such as the need for greater security and speed.
To address the internet’s Achilles’ heel, scientists have turned to quantum physics for its unique and peculiar properties—quantum bits of information, or qubits, that can simultaneously live in a quantum superposition of 0 and 1, in contrast to classical bits of information that are strictly binary.
A quantum computer therefore can solve complex problems much faster than a classical computer, and a quantum communication network has the potential to bring unprecedented capacities for transmitting and processing large volumes of data. Not only does it promise improved speed, a quantum internet can also transmit large amounts of encrypted data, making it unhackable.
Communication in a flash
In a quantum network, the qubits are typically constructed using quantum states of photons, or single particles of light, said Assistant Professor Gao Weibo, an experimental physicist studying photonic quantum computation and communication at Nanyang Technological University, Singapore. Gao was speaking at the recent SupercomputingAsia 2019 conference track on the latest in quantum communication research.
“Photons are great carriers of quantum information because we can control them very precisely. They are also ideal for building a quantum communication network, as they can be coherently transmitted over very long distances,” Gao said.
Gao is part of a larger team led by Professor Pan Jianwei of the University of Science and Technology of China, who is frequently referred to as “the father of quantum.” Under Pan’s leadership, the researchers are feverishly developing technologies that will someday form the backbone of a global quantum network.
“For us to build a quantum network, it will require both the interference and entanglement of individual photons,” said Gao. “Hence, it is important for us to build high-quality single photon sources and efficient photon detectors.”
Compared to the traditional communication networks that are prone to malicious eavesdroppers, a quantum network exploits the unique properties of quantum physics to provide an unbreakable system of information transfer.
The key element that offers protection against interception is something called entanglement, undoubtedly one of the most iconic and intriguing concepts in quantum mechanics. Albert Einstein himself once described entanglement as “spooky action at a distance,” for good reason.
“When two photons are entangled, their properties become so inextricably intertwined that any minute external influences experienced by one of them is instantaneously ‘felt’ by its twin, even if they are placed at two opposite ends of the universe,” Gao explained.
As bizarre as it sounds, entangled photon pairs are critical ingredients for making a secure quantum network possible. For instance, by distributing half of an entangled photon pair to each node of the network, two parties can exchange confidential information by simply implementing specific operations on their half of the entangled pair.
“If there is an eavesdropper, the quality of the entanglement correlations will be irreversibly degraded, allowing us to conclusively certify whether there has been an attempt to ‘steal’ the information,” said Associate Professor Alex Ling, a principal investigator at the Centre for Quantum Technologies in Singapore, also speaking at SupercomputingAsia 2019.
The key to secure communications
While a full-blown quantum network based on this technology might still be in its infancy, specialized functionalities are already within reach today. One such near-term application is quantum key distribution (QKD), which uses entangled photons to provide a shared cryptographic key for two parties to securely exchange messages over conventional networks.
What QKD ensures is that the quantum network will remain robust against future technologies, even the omnipotent quantum computer which threatens to break many of the conventional encryption schemes in a matter of minutes.
“Although the concept of creating entangled photons seems rather complicated, the technology is actually quite mature and accessible now,” Ling said.
“We have started to deploy such entangled photon sources in many different environments outside the laboratory. In fact, one of our systems is currently housed in a shoebox-sized satellite to be launched in collaboration with the Japanese space agency, JAXA.”
Thanks to experimental advancements over a decade, standalone QKD devices can now be easily purchased off the shelf. Quantum networks capable of implementing QKD protocols have also been steadily expanding, both in distance covered and generation rates.
“Progress has been further accelerated by the development of satellite-based QKD schemes, because photons travel over much longer distances through space without getting lost,” Gao added.
Indeed, China’s Micius satellite enabled in 2017 one of the most spectacular demonstrations of QKD technology, by establishing the very first intercontinental video call between Beijing and Vienna that was thoroughly unhackable.
Re-imagining the internet
As we continue to push the boundaries of quantum technologies, the ambition of a large-scale quantum internet is turning into reality. Near-term applications have already been identified, such as precise clock synchronization to efficient verifications of distributed data.
“We can also realize high-precision metrology by exploiting entanglement correlations distributed over large distances. That is why it is so exciting to work with these technologies—there are so many exciting applications to look forward to,” said Ling. “As long as we are sufficiently careful with the human artifacts in the system, the security of such a quantum network can be inherently guaranteed against computational advances.”
Looking further down the road, one can imagine a robust quantum Internet of Things where quantum processors and sensors are securely connected to one another, achieving unparalleled capabilities that are impossible with classical systems.
Although we may not be able to predict exactly when a mature quantum internet would be available for all, one thing remains certain—it will completely transform the way we think about communication, just as the internet did decades ago.
This article was first published in the print version of Supercomputing Asia, July 2019.
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