Written by Raymond Wang
China is making a concerted effort at developing quantum technologies. Some of these technologies – quantum communications, quantum radar, and quantum navigation – have strategic potential, though there are technical hurdles that China will have to overcome if it wants to exploit them. Rather than considering them in isolation, we should instead think systematically about how these technologies interact with each other.
Quantum communications use the quantum states of photons to transmit information, where certain properties of a quantum state, such as spin, represent ‘bits’ of data. Certain protocols use entangled photons, which are pairs of photons that are able to affect each other regardless of the physical distance between them. A team of Chinese scientists recently managed to maintain the entangled state of photons through three metres of seawater – a small distance to us, but a huge distance for a photon – taking the first step towards underwater quantum communications. Quantum communications may be “hack proof,” in that it is impossible to determine the content of an intercepted message, but it is possible to disrupt its transmission. This might bring benefits for China’s ballistic nuclear submarine (SSBN) fleet: should China successfully deploy this technology – and it has shown that it intends to do so, if technological hurdles can be surmounted – it will increase its confidence in the security of their communications.
Quantum radars use entangled photons in a similar way to quantum communications, although with some modifications to account for the fact that the photons are reflected off the detection target. The differences between the returning photon and its unmodified twin are measured, yielding information about the distance, speed, and potentially the material of the target. On September 2016, a team of Chinese scientists from China Electronics Technology Group Corporation’s (CETC) 14th Research Institute announced that they successfully tested a single-photon quantum radar under real-world conditions to a range of 100km – five times that of a prototype developed by an international team of researchers.
Quantum radars potentially have anti-stealth capabilities, provide significantly higher resolution, and have lower energy needs. The military uses of this technology are clear, and Chinese reporting on it has been amusingly explicit – one piece shows the silhouette of a B-2 bomber as a radar target, and claims that this technology will have applications in “strategic early-warning (战略预警)” and “missile defence”, potentially contributing to a future launch-on-warning posture. Of course, any system would need a range far beyond 100km to have these effects, and again there are a host of limiting factors to overcome. Based on grant announcements and the CETC announcement, though, China intends to pursue this technology further.
A key question is whether or not it is possible to operate a quantum radar at over-the-horizon (OTH) frequencies (ranging from 2-50MHz), as the technologies that China claims to be investigating would not allow this. If not, China would have to deploy airborne radar to extend the effective range of the system, which would therefore be limited by the extent of China’s ability to provide friendly air cover
Finally, quantum navigation potentially offers high-precision navigation and positioning, with consequences for missile accuracy, especially for SLBMs – a large part of hitting a target accurately is knowing where you are launching from. Quantum navigation measures how low-energy atoms react to changes in local magnetic and gravitational fields. Recently, China reportedly achieved related breakthroughs: first, in key technologies associated with a magnetic resonance spin gyroscope; and second, in successfully launching a cold atomic clock into space.
These analyses are individually interesting, but how would these technologies interact with each other if deployed, and how would they interact if they were deployed by two sides in relative parity? For example, China might currently target U.S. satellites in a conflict because the latter is more reliant on them. But quantum communications for military purposes will rely heavily on quantum satellites, so if China adopted this technology then it would plausibly make her equally reliant on satellites. Would this create incentives for both sides to exercise restraint on anti-satellite operations?
Another question is how will quantum communications affect the cyber offense-defence balance? It is often assumed that the cyber domain favours the offensive side, but quantum communications seems to take away part of the attack surface. To be sure, devices will remain vulnerable, but attacks targeting communications would face challenges. Furthermore, is ‘absolute’ communications security a stabilizing factor in a crisis situation? One party may well enjoy increased confidence, but what about the other side, which cannot gain as much from signals intelligence as before?
Finally, assuming that the U.S. and China deploy these technologies in relative parity, there will be various loci at which these technologies interact. Quantum navigation could make Conventional Prompt Global Strike even more accurate, elevating Chinese fears of a conventional strike eroding its strategic assets. How will such worries offset the sense of security they gain from technologies such as quantum radar?
Some might think these scenarios fantastical. But I don’t think we currently have a systematic way of thinking through how these technologies might interact. I believe the time to develop this is sooner rather than later, and hopefully these scenarios will catalyse a discussion that will lead us there.
Raymond Wang is a Graduate Research Assistant at the James Martin Centre for Nonproliferation Studies, and an MA candidate at the Middlebury Institute for International Studies at Monterey.
Banner image courtesy of Wikimedia Commons.