Google announced last month that their “quantum computer” only took 200 seconds to solve a mathematical problem that would take the fastest supercomputer in the world 10,000 years. Such a powerful “quantum machine”, like the machine Benedict Cumberbatch built in the movie The Imitation Game to decipher the Nazis’ encrypted messages, makes Google the front runner of the “quantum computer” race, where other leading technology companies such as IBM, Microsoft, and Intel are not absent. It is also believed that the national security and the electronic commerce worthy of billion dollars will be forced to face unprecedented security treat from the “quantum computers”.
Under the waves of “quantum threat”, scientists are speeding up the pace to develop the “quantum encryption” against the attacks potentially from the quantum computers. In the movie Avengers: Infinity War, the Avengers desperately hope to use the magic of the quantum world to save the future. Coincidentally, this is the path scientists are taking, too. In 2016, the scientists from University of Science and Technology of China used the low-Earth-orbital satellite to confirm the feasibility of “quantum encryption” in the long-distance communication. The new technology, relying on the same quantum physics as the quantum computers, prevents the communication from hacking and even alarms you when the hackers are present.
Chih-Sung Chuu, a professor of the Quantum Communication Division at the Center for Quantum Technology, leads a group of graduate students (Sheng-Hsuan Huang, Yung-Cheng Kao, Chih-Hsiang Wu, Chin-Hsuan Chang) from National Tsing Hua University to complete the first demonstration of the quantum encrypted communication in Taiwan. Chuu and his team uses “photons”, the particles that constitutes a light beam, to transmit the key for encryption. In the quantum world, these tiny particles exhibit many extraordinary properties. The superposition, a quantum property allowing a particle to make “clones” of itself, is just one of them. This “quantum cloning” not only enhances the computing efficiency of the quantum computers, but also gives the quantum encrypted communication the absolute security it needs.
Nevertheless, the outdoor environment brings challenges to implement the quantum encrypted communication. In order to reduce the disturbances from the fluctuation in temperature and vibration, Chuu and his team distribute a photon evenly in several pulses before letting it enter the Campus Optical Fiber Network to transmit the key. After the photons arrive the receiver’s “quantum decoder”, they are analyzed to generate the key, which can then be used by the “One-Time-Pad” for encrypted communication. Chuu’s work is supported by the Taiwan Ministry of Science and Technology and Ministry of Education, and benefits from the assistances of Kai-Ming Feng’s team of the Institute of Communications Engineering, the Computer and Communication Center of National Tsing Hua University, and the Information Technology Service Center of National Chiao Tung University. Chuu’s next step is to set up a quantum communication network next to the Hsinchu Science Park, preparing for an even larger network in the future. Although Taiwan started late in the development of quantum communication, Chuu’s plan ensures Taiwan to be part of the “quantum Avengers” against the “quantum hackers” who use quantum computers.
Illustration of the quantum encrypted communication network (the completed and planned channels are indicated by the solid and dash lines, respectively)
Technical Details of Quantum Encrypted Communication
Transmission channel: Campus optical fiber network
Transmission distance: 3.44 km
Key distribution protocol: Differential phase shift protocol
Encoding type: Phase
Encryption application: One time pad
Light source: Weak coherent light pulses
Wavelength: 1550 nm
Number of pulses of a photon: 3
Average photon number: 0.1
Pulse width: 5 ns
Generated key rate: 1.5 Mbit/s
Received key rate: 140 kbit/s
Bit error rate: 2.5 %
Quantum efficiency of detectors: 10 %
Dark count of detectors: 80 Hz
Dead time of detectors: 2 μs
Media Contact
Professor Chih-Sung Chuu
Department of Physics, National Tsing Hua University
TEL: (03)5742548
Email: cschuu@phys.nthu.edu.tw
Professor Chung-Yu Mou
Center for Quantum Technology & Department of Physics
National Tsing Hua University
TEL: (03)5742537
Email: mou@phys.nthu.edu.tw
Dr. Lien-Hsuan Lin
Department of Natural Sciences and Sustainable Development
Ministry of Science and Technology
TEL: 02-27377514
Email: lhlin@nstc.gov.tw
