Given the potential implications of novel quantum technologies for defence and security, NATO has identified quantum as one of its key emerging and disruptive technologies. This article seeks to unpack some of the fascinating future applications of quantum technologies and their implications for defence and security.

Those who are not shocked when they first come across quantum theory cannot possibly have understood it.

If you think you understand quantum mechanics, you don’t understand quantum mechanics.

Not only is the Universe stranger than we think, it is stranger than we can think.

Three quotes from three famous quantum physicists. I guess it is safe to say that there is broad consensus that trying to understand quantum mechanics is not your average Sunday morning brain teaser. However, quantum mechanics is not just mind-boggling and food for vigorous thought. In fact, although we might not be able fully to comprehend it, technologies built upon our understanding of quantum mechanics are already all around us.

Transistors and semiconductors in our computers and communication infrastructures are examples of ‘first generation’ quantum technologies. But the best is still to come. Through a greater understanding of quantum phenomena such as ‘superposition’ and ‘entanglement’ (explained below), the ‘second quantum revolution’ is now taking place, enabling the development of novel and revolutionary quantum technologies.

As these technologies will bring profound new capabilities both for civilian and military purposes, quantum technologies have received significant interest from industry and governments in recent years. Big technology companies like IBM, Google and Microsoft are spending hundreds of millions of dollars on research and development in the area of quantum computing in their race for ‘quantum supremacy’. Similarly, governments have recognised the transformative potential and the geopolitical value of quantum technology applications and the United States, the European Union and China have each set up their own >1 billion dollar research programmes.

Principles underlying quantum technologies

Without going into a detailed explanation of quantum mechanics, a few key underlying principles are worth briefly discussing to help understand the potential applications of quantum technologies.

Quantum technologies exploit physical phenomena at the atomic and sub-atomic scale. Fundamental to quantum mechanics is that at this atomic scale, the world is ‘probabilistic’ as opposed to ‘deterministic’.

This notion of probability was the subject of a world-famous debate between Albert Einstein and Niels Bohr at the fifth Solvay Conference on Physics, held in October 1927 in Brussels. This conference gathered the 29 most notable physicists of the time (17 of them would later become Nobel Prize winners) to discuss the newly formulated quantum theory.

In the so-called “debate of the century” during the 1927 Solvay Conference, Niels Bohr defended the new quantum mechanics theory as formulated by Werner Heisenberg, whereas Albert Einstein tried to uphold the deterministic paradigm of cause and effect. Albert Einstein famously put forward that “God does not play dice”, after which Niels Bohr countered “Einstein, stop telling God what to do.”

Nowadays, the scientific community agrees that Niels Bohr won the debate. This means that our world does not have a fixed script based on cause and effect but is in fact subject to chance. In other words, you can know everything there is to know in the universe and still not know what will happen next.

This new probabilistic paradigm led the way to a better understanding of some key properties of quantum particles which underlie quantum technologies, most notably ‘superposition’ and ‘entanglement’. The improved understanding of these fundamental quantum principles is what has spurred the development of next-generation quantum technologies: quantum sensing, quantum communication and quantum computing.

Present and future applications

While quantum computing has received most of the hype around quantum technologies, a whole world of quantum sensing and quantum communication is out there, which is just as fascinating and promising.

Quantum sensing

Quantum sensors are based on ultra-cold atoms or photons, carefully manipulated using superposition or entanglement in specific ‘quantum states’. By exploiting the fact that quantum states are extremely sensitive to disturbances, quantum sensors are able to measure tiny differences in all kinds of different properties like temperature, acceleration, gravity or time.

Quantum sensing has transformative potential for our measurement and detection technology. Not only does it enable much more accurate and sensitive measurements, it also opens up possibilities to measure things we have never been able to measure before. To name a few, quantum sensors could allow us to find out exactly what lies under our feet through underground mapping; provide early-warning systems for volcanic eruptions; enable autonomous systems to ‘see’ around corners; and provide portable scanners that monitor a person’s brain activity (source: Scientific American).

While quantum technologies might seem to be technologies of the distant future, the first quantum sensors are actually already on the market (for example, atomic clocks and gravimeters). Looking ahead, we can expect more quantum sensing applications becoming available over the course of the coming five to seven years, with quantum Positioning Navigation and Timing (PNT) devices and quantum radar technologies as particular applications to look out for.

Quantum communication

The potential of quantum communication relies on its promise to enable ‘ultra-secure’ data communication, potentially even completely unhackable. Currently, our exchange of data relies on streams of electrical signals representing ‘1s’ and 0s’ running through optical fibre cables. A hacker who manages to tap into these cables can read and copy those bits as they travel through the cable. In quantum communication on the other hand, the transmitted information is encoded in a quantum particle in a superposition of ‘1’ and ‘0’, a so-called ‘qubit’. Because of the sensitivity of quantum states to external disturbances, whenever a hacker tries to capture what information is being transmitted, the qubit ‘collapses’ to either a ‘1’ or a ‘0’ – thereby destroying the quantum information and leaving a suspicious trail.

The first application of quantum communication is called ‘Quantum Key Distribution’ (QKD) which uses quantum particles for the exchange of cryptographic keys. In QKD, the actual data is transmitted over traditional communication infrastructure using normal bits, however, the cryptographic keys necessary to decrypt the data are transmitted separately using quantum particles. Extensive experimentation in QKD is already taking place, both using terrestrial communication as well as space-based communication. In 2016, China launched the world’s first quantum science satellite ‘Micius’, which has since then demonstrated intercontinental ground-to-satellite and satellite-to-ground QKD by securing a video conference meeting between Beijing and Vienna (source).

‘Quantum teleportation’ would be the next step in quantum communication. Whereas in QKD the cryptographic keys are distributed using quantum technology, with quantum teleportation it is the information itself that is being transmitted using entangled quantum pairs. The greatest distance over which quantum teleportation has been achieved so far over fibre-optic cable is 50 kilometres (source), and the challenge in the coming years is to scale quantum teleportation to enable secure communication over larger distances.

The ultimate goal in quantum communication is to create a ‘quantum internet’: a network of entangled quantum computers connected with ultra-secure quantum communication guaranteed by the fundamental laws of physics. However, a quantum internet not only requires quantum teleportation over very large distances, it would also require the further development of other crucial enabling technologies like quantum processors, a comprehensive quantum internet stack including internet protocols and quantum internet software applications. This really is a long-term endeavour and, while it’s difficult to determine if and exactly when this technology matures, most scholars refer to a time horizon of 10-15 years.

Quantum computing

Quantum computing will significantly increase our capacity to solve some of the most complex computational problems. In fact, quantum computing is said to be as different from classical computing, as a classical computer differs from the abacus.

As explained above, whereas classical computers perform calculations using binary digits (0 or 1), quantum computers represent information using quantum bits (qubits) which can be in a superposition of both states (0 and 1 at the same time).

As qubits are extremely sensitive to external disturbances, in order to be able to control, manipulate and exploit them, qubits need to be cooled down to a level extremely close to the absolute minimum temperature (or zero kelvin), around 15 millikelvins. That is colder than outer space! In fact, inside a quantum computer is the coldest place in the universe we know of.

Qubits enable quantum computers to make multiple calculations at the same time, potentially resulting in an immense increase in computational efficiency as opposed to classical computers. There are a number of applications where quantum computers will be particularly transformational:

Simulation of physical systems for drug discovery and the design of new materials;

Solving complex optimisation problems in supply chain, logistics and finance;

Combination with artificial intelligence for the acceleration of machine learning;

Factorisation of integers, enabling the decryption of most commonly used cybersecurity protocols (e.g. RSA, an asymmetric encryption algorithm, used for secure data transmission).

Big technology companies like IBM, Google and Microsoft are racing for ‘quantum supremacy’, which is the point where a quantum computer succeeds in solving a problem that no classical computer could solve in any feasible amount of time.

In October 2019, Google claimed to have achieved quantum supremacy on its 53-qubit quantum computer. However, critics say that the problem solved in the Google experiment had no practical value and that therefore the race for quantum supremacy is still on.

Current quantum computers have around 60 qubits but further developments follow each other in rapid succession and ambitions are high. Last September, IBM announced a road map for the development of its quantum computers, including its goal to build a quantum computer with 1000 qubits by 2023 (source). Google has its own plan to build a million-qubit quantum computer by 2029 (source).

With 1000-qubit quantum computers, so-called Noisy Intermediate-Scale Quantum (NISQ) computers, we can already see some valuable practical applications in material design, drug discovery or logistics. The coming five to ten years therefore will be incredibly exciting for quantum computing.

Implications for defence and security

Quantum technologies have the potential to bring profound new capabilities, enabling us to sense the insensible, transforming cybersecurity, and enabling us to solve problems we have never been able to solve before.

In the defence and security environment, two applications will have particularly significant implications in the near- to mid-term.

Firstly, quantum sensing. Quantum sensors have some promising military applications. For example, quantum sensors could be used to detect submarines and stealth aircraft, and quantum sensors could be used for Position, Navigation and Timing (PNT). Such ‘quantum PNT devices’ could be used as reliable inertial navigation systems, which enable navigation without the need for external references such as GPS. This would be a game-changing capability for underwater navigation on submarines, for instance, but also as a back-up navigation system for above-water platforms in case of GPS signal loss.

The first quantum sensors are already commercially available, making it the most mature technology out of sensing, communications and computing. Moreover, for quantum communications and computing, the civilian sector is expected to drive developments forward, given the immense potential value they have for civil industry. However, for quantum sensing, potential applications such as quantum PNT and quantum radar are particularly interesting for the military. Therefore, it is up to the military to fund, support and guide research and development in this area to make these potential applications a reality.

Secondly, the ‘quantum threat’ posed by quantum computing. As mentioned in the previous section, the factorisation of integers is one type of problem that quantum computers can solve particularly efficiently. Most of our digital infrastructure and basically anything we do online – whether that is video conferencing, sending e-mails or accessing our online bank account – is encrypted through cryptographic protocols based on the difficulty of solving these kinds of integer factorisation problems (e.g. the RSA algorithm). While practically usable quantum computers still need to be developed, the quantum algorithm to solve these problems and to decrypt our digital communication, i.e. Shor’s algorithm, has already been invented in 1994 and is waiting for a quantum computer capable of running it.

To illustrate, the figure below is an example of an integer factorisation problem as used to secure potentially sensitive information.

While you might think that any graphic calculator would be able to solve this seemingly simple mathematical problem, in fact, the world’s fastest supercomputer would take the whole lifetime of the universe to solve it. A quantum computer, however, would be able to solve it in a couple of minutes (source).

This is an urgent threat to society writ large but also specifically to the military, given the importance of secure communication and secure information for defence and security. To counter this threat, we will have to completely upgrade all our secure digital infrastructure using cryptography that is ‘quantum-resistant’, i.e. secure against both quantum and classical computers. One option would be to wait for quantum communication (QKD or quantum teleportation) to mature and use this quantum technology to protect against the other quantum technology. However, time is not on our side. Not only could quantum computing technology outpace quantum communication development, the threat is already present. With the prospect of future quantum computers, hackers could steal encrypted information today, store it and decrypt it in 10-15 years using a future quantum computer.

The better option is to implement ‘Post-Quantum Cryptography’ (PQC), new classical (i.e. non-quantum) cryptographic algorithms that even quantum computers will not be able to solve. Currently, the US National Institute of Standards and Technology (NIST) is leading an international competition to select the PQC algorithm(s) to be standardised and adopted across the globe. The process started in 2016 and in July 2020 the NIST announced it had seven final candidates.

We can expect the NIST to make its final selection for standardisation by early 2022 and establish actual standards by 2024 (source). Decision-makers across industries and within the military should pencil these dates in their diaries, start preparing for a big cybersecurity upgrade and make sure we hit the ground running.

Way ahead

New advances in quantum technology research and development have the potential to bring exciting new capabilities to the military. Given the sizable interest and funding for quantum technologies coming from both civilian industry and governments, it is expected that the technology will mature and that new quantum applications will become available in the coming five to ten years. However, for Allied militaries to be able to actually reap the benefits of these new quantum technologies, it is essential that Allies proactively engage in this field and guide the development and adoption of the military applications of quantum technologies. This should include not just engaging with big technology companies, but specifically also with start-ups, universities and research institutes as these are vital for innovation in these new technologies.

Allied militaries could bring significant added value to existing efforts in industry and academia by providing testing & validation infrastructure (test centres) and access to end-user military operators. Early experimentation with these technologies not only contributes to their further development, but also enables the military to become familiar with these technologies and their capabilities, which helps facilitate future adoption. Moreover, active participation in the quantum ecosystem increases the military’s understanding of the potential risks associated to quantum technologies, specifically within the cyber domain.

**This is the fifth article of a mini-series on innovation, which focuses on technologies Allies are looking to adopt and the opportunities they will bring to the defence and security of the NATO Alliance. Previous articles:**