Canadian Researchers Join Effort to Establish Satellite-Based Quantum Communications Link

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The Three-Year Hyperspace Collaboration Aims to Demonstrate the Feasibility of Using Satellites to Facilitate Long-Distance Quantum-Secured Communications

Earlier this year, Professor Li Qian of the University of Toronto and Professor Thomas Jennewein  of the University of Waterloo announced that they would be collaborating with researchers and partners from five countries to establish a quantum satellite communications link between Canada and the European Union.

The goal of this collaboration is to demonstrate the feasibility of satellite-based quantum communications technologies, which the researchers believe will be essential for future applications, such as a “quantum internet” for secure data transfers.

Quantum Communications Are Inherently More Secure and Resistant to Interception by Eavesdroppers

One of the drivers behind the recent push to develop quantum communications networks is the fact that they are inherently more secure than conventional telecommunication methods.

In conventional networks, data is transmitted as a series of optical or electrical pulses. These pulses represent bits of information, with each bit having a discrete value of either 1 or 0. As these bits of information are transmitted, they can be intercepted and read by eavesdroppers along the network. To combat this potential for eavesdropping, many data encryption techniques were developed. These techniques typically involve using a mathematical algorithm to scramble the sequence of 1s and 0s which represent a sensitive piece of data. The scrambled data would then be sent to the intended receiver along with an encryption key that can be used to unscramble the bits back into their original sequence. However, because both the encrypted message and the encryption key are sent via conventional networks, eavesdropping can still occur in cases where a third party is able to intercept both elements of the encrypted transmission.

In contrast, quantum encryption techniques exploit the unique properties of qubits to ensure data security. Unlike classical bits, qubits exist in highly fragile quantum states and can simultaneously have values of both 1 and 0. However, these fragile quantum states collapse down into discrete values of 1 or 0 as soon as they are observed. As a result, it would be impossible for an eavesdropper to intercept a quantum-encoded message without leaving behind a telltale footprint of their activities. In order to take advantage of this unique property of qubits, researchers developed techniques such as quantum key distribution (QKD), which involves using quantum networks to transmit encryption keys. When signs of interception are detected, the key is discarded, and new keys are sent until one is able to reach the intended receiver in an untampered state. Because this security is derived from fundamental laws of physics, quantum communications will remain secure even with future advances in computing power.

The Emptiness of Space Allows for Transmission Over Longer Distances

While quantum communication offers enhanced security compared to conventional telecommunication, one major challenge relates to the difficulty of transmitting quantum information over long distances. Specifically, photon-based qubits can only be transmitted through optical fibre cables for a few hundred kilometers before the signal becomes unreliable, as the photons will eventually be absorbed by the material of the optical fibre. Furthermore, conventional signal amplification techniques are not compatible with the unique physical properties of quantum particles. For this reason, researchers have begun looking to space. Because signals from satellites spend most of their journey traveling through empty space, signal integrity can be maintained over a much larger distance.

Potential Challenges that Lie Ahead

While the emptiness of space allows for reduced photon loss, the Earth’s atmosphere continues to pose a challenge for the final leg of a quantum signal’s journey. For example, atmospheric turbulence and thick cloud coverage may both cause signal degradation. To counteract these effects, the researchers will attempt to improve the robustness of the signals by entangling the photons in multiple degrees of freedom (e.g., frequency, time, polarization). The researchers will also have to limit their testing to nighttime to avoid sunlight interference. However, despite the many challenges that lie ahead, the researchers remain optimistic and believe that the findings of the HyperSpace collaboration will make “quantum applications attractive and realistic in the near future.”

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