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?

Yes and no. What makes the satellite unique is the distance over which quantum entanglement and quantum communication are being tested. Until now, most studies of quantum entanglement involve much smaller distances in labs, and thus a successful deployment could potentially expand the types of possible quantum communication networks.
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?

The narrative of a demise in American technological innovation certainly garners attention, but is greatly exaggerated. Pointing to declining US government spending in basic research does not capture the full story. Many quantum computing projects and research are classified, and that funding is not available in the public domain. Additionally, shepherding any emerging technology from basic research to a useful product requires a complex ecosystem of academic research, government support, and private sector funding. There are many strong links between academic institutionsnational labs, and US government agencies in the field of quantum computing that have advanced this technology. In terms additional funding sources, the US also has venture capital firms such as the Quantum Wave Fund and In-Q-Tel investing heavily in this space. While basic research could be enhanced with more funding, characterizing the US as falling behind in quantum computing is unnecessarily pessimistic and ignores important synergies between private and public sector actors in the US scientific community that have already produced breakthroughs in quantum technologies. 
As the physicist leading the quantum satellite communication project Pan Jianwei said, “I think China has an obligation not just to do something for ourselves … but to explore something unknown.” The launch of the Chinese quantum satellite is not yet a breakthrough moment in the field of quantum communication, but could spur interesting developments and is a step toward better understanding the unknowns surrounding 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.