China’s QUESS: What you should know about China’s Quantum Experiments at Space Scale (QUESS)
By Katrina Timlin
This week, China launched its first quantum communications satellite. While this event is an important step for quantum communication research, media and news coverage of the launch mischaracterize the field of quantum computing. In this post I explain common misconceptions about quantum communication and quantum cryptography.
1. Is quantum cryptography un-hackable?
Quantum cryptography can be hacked - even when transmitted via satellite. The security benefits of quantum technologies arise from being immediately able to see when someone is tampering with communication, rather than from preventing this tampering. This is due to the quantum property of decoherence - when observed or measured, a quantum particle ‘loses’ its quantum state of superposition and becomes a regular particle. Therefore, any third party interference would change the message and the recipients, Alice and Bob, would immediately know that someone is listening to their conversation. Alice and Bob could both independently identify that the key they were using is now obsolete and that the communication channel had been identified, rendering this channel unsafe or incapable of transmitting messages. Even if the eavesdropper might not be able to read the message (and skillful hackers might be able to do so), she has nullified the main purpose of the quantum communication channel – sending secure messages. To create fully secure quantum communication channels, you would need to have some low probability of intercept technique incorporated into the design of a quantum communication system. Novel hardware and software to prevent interference with quantum communication is needed to make these systems truly ‘unhackable’.
Ned Allen, Lockheed Martin’s Chief scientist, spoke about the myth of ‘unhackable’ quantum communications on our podcast.
2. Is quantum communication faster than the speed of light?
Quantum communication at this speed this would invalidate a fundamental law of Einstein’s rational universe – that nothing can move faster than the speed of light. This is a subject of active debate and research in the scientific community, and recent experiments have called the impossibility of faster-than-light communication into question. Some, however, believe that “spooky action at a distance” is not actually ‘action’ – what is happening with entanglement does not completely resemble our understanding of action exerted on particles. More research is needed to better describe the correlation of entangled quantum particles and how this can be practically utilized.
Seth Lloyd, a professor of mechanical engineering and physics at MIT, explains this common misconception about quantum communication.
3. Is this Chinese satellite at the forefront of quantum communication?
Some secure quantum communication, however, are fairly well developed and already deployed. Companies including ID Quantique and Quintessence labs offer quantum key distribution* and quantum encryption technologies, and have been doing so for years. Additionally, quantum communication through space is relativity untested in practice, although researchers believe it is possible. Other methods of transmitting quantum information, for example, through optical fiber, might be a more resilient way to communicate and offer more possibilities when designing a communication network. It is uncertain whether the next breakthrough in quantum communication will come from a space-based platform.
4. Is the U.S. falling behind in quantum information science?
*Quantum key distribution involves the exchange of keys between two users. The key is then used to encrypt and decrypt messages. This is technically not quantum cryptography, as it involves the exchange of keys and not transmission of a message.