Quantum technology is a growing field, and its subset, quantum communications, has many applications within the space industry. On a recent episode of Constellations Podcast, SQT CEO David Mitlyng joined John Gilroy to explain the growing field of quantum communications. SQT is one of a handful of companies specializing in this technology, and claims to transform the world’s networks for the “quantum revolution.”

In this exclusive interview, Constellations sits down with Mitlyng to discuss applications beyond Quantum Key Distribution (QKD) and Quantum Clock Synchronization (QCS), how this technology can strengthen network security, and its international defense implications.

Constellations: For those who haven’t yet listened to your podcast episode, in a few sentences, could you describe what the field of quantum communications is and how it relates to the space industry?

David Mitlyng: Quantum communications is a new type of communications, where you are manipulating the quantum properties of photons, or particles of light. All other types of long-distance communication rely on the modulation of a signal, which is another way of saying that you are changing the flow of photons on an RF or an optical beam, and transmitting information that way. In quantum communications, we now have the capability of creating, manipulating, and detecting individual photons. That is creating a new paradigm in communications because those quantum properties of photons have inherent security that ensure that only the two parties trying to communicate can read the message.

Constellations: In your Quantum Communications: A Primer paper, you say there are different flavors of quantum communications. What did you mean by that?

Mitlyng: Quantum communications relies on manipulating the quantum properties of photons. There are a couple of different ways to do this; a couple of different “flavors.” One of the more common ways is prepare and measure. Essentially, you’re preparing the quantum properties of a photon, usually the polarization, and only the two parties that are trying to communicate know the way it’s prepared. That’s how you thwart an eavesdropper, a “man in the middle” who is trying to intercept the encryption keys that they’re trying to send between them.

The other flavor is entanglement - you start with a weak laser that produces a stream of photons that are converted into pairs of photons that are entangled. Those photons are then sent to the two parties that do their individual measurements to get their string of bits, for example. And again, that is also secure. Because if an eavesdropper tries to intercept the photon, the other party would break the entanglement.

Constellations: In the podcast you spoke about Quantum Key Distribution (QKD) and Quantum Clock Synchronization (QCS) as applications for quantum communications. Are there any other applications currently being developed? How could they be used within the space industry?

Mitlyng: You mentioned two of the major applications, the most famous of which is QKD, which is using quantum-manipulated photons to securely distribute encryption keys. Then those keys are used to encrypt normal messages.

The other application you mentioned is QCS. When you have the quantum properties of the photons, you can use that to synchronize the clocks between the two parties very accurately and very securely. But there are other applications even beyond that.

There’s quantum random number generation: When you are creating these quantum properties of photons, they are inherently random, so there is value for certain groups to have provably random numbers.

Then, there’s a couple of very interesting long-term applications, like quantum networking and quantum radar. Quantum networking is getting a lot of development focus because you can use the quantum properties of photons to network quantum computers. This is euphemistically referred to as the “quantum internet.” One of the ways you manipulate the quantum properties of photons is with entanglement, and quantum computers rely on entanglement to create qubits. You can have these quantum networks, quantum computer networks, via entanglement distribution, and satellite is the best way to do this. It has a broad global reach. There have been a lot of papers and articles written about how that could be more valuable or a better use of these applications than existing fiber networks.

Constellations: It seems like a lot of quantum communications focuses on the satellite. How could quantum technology change or improve operations on the ground? Additionally, how could this technology improve communications within the space network?

Mitlyng: Well, quantum communications is ideally suited for satellite communications, because it can cover a longer range. The photons can be distributed via fiber, but they have a limited range - roughly about 100 kilometers. The glass in the fiber cable attenuates the photons so that you will need repeaters, but repeaters aren’t secure.

We look at quantum communications as a way to augment existing satellite networks and systems. For example, you can use QKD with a quantum link to securely distribute encryption keys that are then used to encrypt the normal communications that are distributed via satellite. This can then be used to secure communications between ground stations, or even to encrypt satellite downlink data, telemetry or commands.

Quantum communications can also be used for QCS, which provides time synchronization for satellites and ground networks, which is also critical for telecommunications and financial networks. So for a satellite operator, particularly satellite operators that are already considering adding optical communications to their satellites, adding quantum communications gives that network extra security and synchronization that could bring value to the satellite operator’s business.

Constellations: Speaking of optical communications, you say that quantum communications is related to optical communications. How? Is it also a competitor to more traditional RF?

Mitlyng: The scientific answer is that the photons used in quantum communications are roughly in the same wavelength as optical communications. That allows you to use a lot of the same hardware as optical communication systems. For satellites that already have optical communication systems, you can use the same pointing and tracking mechanism. The side effect is that, like optical communications, quantum communications is very directional and does not penetrate clouds or walls. That’s part of the reason it’s so secure. But it also means that it won’t readily replace RF communications anytime soon. You want to look at quantum communications as providing applications that will augment the capabilities of traditional RF networks.

Constellations: You also say that the value of quantum communications is primarily due to its security. So, how can this technology be used in a defense context?

Mitlyng: Anywhere you need secure communications, quantum communications should be a critical addition to augment your existing network. Milsatcom, just like commercial secure communications, requires encryption, which requires encryption keys. The distribution of encryption keys is a tricky and expensive business. Particularly in the defense sector, where there is concern about having encryption boxes or the distribution of encryption keys to bases or troops out in the field. QKD provides an extra level of security for the distribution of those encryption keys, which will then create that extra level of security for the network.

Constellations: You spoke about China being far ahead of other nations in developing a quantum network. How did they get so ahead? What needs to happen for the rest of the world to catch up?

Mitlyng: Well, it’s an interesting question. If you look at the history of quantum communications, particularly QKD, the U.S. was the initial leader. The initial QKD protocols were developed at IBM labs a lot of research was being done in the U.S. as well as Europe. But about a decade ago, the Chinese took a very focused effort on this technology, particularly developing practical QKD systems. They funded it well, and beat everybody to the punch with the launch of the world’s first QKD satellite called Micius in 2016. Since the satellite was launched, it has done three groundbreaking space to ground quantum experiments. The Chinese government has really ramped up their efforts into this development. They’ve put billions of dollars into follow-on research and development, with plans that they’ve announced to create terrestrial QKD networks, as well as a satellite constellation with LEO and GEO satellites, and hundreds of ground stations around the world. I think there’s a recognition that they are the clear world leaders in this area.

Now, what can the rest of the world do to catch up? The obvious answer is more investment, more funding. Within Europe, there’s the 1 billion Euro quantum initiative that’s going on. In the United States, there’s a $1.2 billion National Quantum Initiative Act that was signed into law in late 2018. So, it’s a little bit of catch up, but there’s a very focused effort now to reclaim the lead. I give credit to organizations like the Quantum Economic Development Consortium, QED-C - it was kicked off with the funding from the National Quantum Initiative Act as a way of coordinating how that funding is allocated, to ensure that we’re properly allocating the resources to catch up on this critical technology.