Riding the wave in quantum photonics

Tell us about Quantopticon and the problems you’re hoping to solve for the quantum community.

Mirella Koleva, chief executive officer: As quantum physicists, materials scientists and engineers, we are working together to build so-called “quantum 2.0” devices that exploit the properties of superposition and entanglement. But we need to understand the fundamental physical processes occurring within these devices before we can design them better, so at Quantopticon we are developing simulation software that accurately predicts light–matter interactions in the quantum realm. Our software is intended to be a platform for designing and optimizing solid-state quantum photonic components, networks and devices.

How did you get the idea to start the company?

Gaby Slavcheva, chief scientific officer: Having worked in quantum and nonlinear semiconductor optics for many years, I was aware of the methods for modelling and simulating lasers. However, lasers are classical devices in terms of the statistics of radiation they emit, and in recent years we have witnessed great progress towards the physical realization of Richard Feynman’s quantum-computing paradigm based on fragile quantum properties such as quantum coherence, superposition and entanglement. Global research efforts are now focused on developing these next-generation technologies and, ultimately, a universal quantum computer. 

The photonic quantum-computing modality has great advantages in terms of scalability and speed compared to other quantum computing architectures. But the theory and modelling of these quantum 2.0-type effects are in their infancy, and advanced computational tools are needed to predict the performance of devices based on photonic platforms. So Mirella and I decided to found Quantopticon to address this growing need and the lack of such modelling tools for quantum photonics in particular. We aim to accelerate the advent of groundbreaking quantum 2.0 devices and to facilitate their widespread adoption.

What was the catalyst that made you say, “Right, we’re going to start a company together?”

MK: I think there has been a natural build-up of the readiness of quantum technologies in the last five years. When we started the company in 2017, we were anticipating this progress and we thought, “This is the moment when we really need to jump in and get involved to ride on this wave.” So we picked the right moment.

We have very ambitious plans to develop our software suite so that we can really make a difference in the various sub-sectors of the quantum technology industry

Part of riding the wave, of course, is getting funding. How did you do that?

MK: In the very early days, we applied for funding from Innovate UK, the UK’s innovation agency, which provides grants for innovative businesses like ours. We teamed up with world-leading experimentalists in quantum optoelectronics at the University of Oxford and experts in gallium nitride at the University of Cambridge and we wrote a project proposal together. The idea was to use indium gallium nitride quantum dots embedded in gallium nitride micropillar cavities as a test bed for our software. The funding we obtained from Innovate UK also helped us to develop a graphical user interface for our software and to accelerate the underlying code.

The biggest funding hurdle for us – in fact, the most difficult hurdle we’ve had to overcome – was trying to obtain follow-on funding after the Innovate UK project finished. We had a funding gap during the COVID pandemic crisis and that was a really hard time. For nearly three years we repeatedly applied to Innovate UK and other UK government funding agencies, to the extent that we spent most of our time writing grant proposals rather than developing the company. But these grant proposals were ultimately not chosen for funding. That was a real low point. We got so discouraged that we started looking for financing from abroad.

After some sacrifices, grit and sheer determination, the European Space Agency came to our rescue by commissioning us to design components for the first European quantum encryption satellite. At around the same time, we won a significant amount of money from Duality, a start-up accelerator programme based at the University of Chicago in the US that focuses on ventures rooted in quantum technologies. We were the only non-US company to be accepted onto the programme and relocating to Chicago was part of the requirements, so I’m staying in the US until at least August 2022. Finally, in January we were awarded a further small sum from the SPIE in their Startup Challenge competition at Photonics West. It’s a bit ironic and slightly sad that we are getting so much recognition from the rest of the world, but not from our home country. We hope this will change.

How has Duality helped you?

MK: It has provided a wealth of support, mentoring and courses, as well as opportunities to showcase ourselves at high-profile events and summits. It’s been incredibly rewarding to be part of both Duality and the other start-up accelerator programme that we are in, which is based at the University of Toronto, Canada, and is called Creative Destruction Lab. The two programmes have completely different ways of supporting ventures and they complement each other well. We’re very lucky to be in both at the same time.

What do you see as the main challenges for the field of quantum technology as a whole? 

GS: The main technical challenge is undoubtedly the physical realization of a universal quantum computer. A useful photonic quantum computer that can demonstrate quantum advantage over classical computation needs at least a million interconnected qubits to provide an overhead for quantum error correction. Such large-scale architectures require ultrafast operations and interconnects, hence the demand from industry to develop high-speed and high-fidelity quantum components such as quantum light sources. 

Developing the kind of fast, scalable architecture needed to ensure the entanglement of a large number of qubits with minimum decoherence and optimized error correction is a formidable task that is currently being attacked from many angles and on different computing platforms. We believe that by creating reliable physical models of quantum phenomena and computerized design tools for integrated quantum phonics on a chip, we can help to develop such highly performing individual components. These components then need to be entangled, and computational modelling can help here, too, similar to the way that electronic design automation tools are used nowadays as a matter of course in electronic circuit design.

MK: On the business side, the main challenge in the field is that the quantum industry is still emerging and it’s not clear how it will grow in the future and how it will develop. Even the biggest experts are not sure what is going to happen next. So it’s very challenging for a new entrepreneur like myself who doesn’t have a lot of experience in this area to plan, and especially to make long-term plans about how our company is going to develop in the next several years. We are aware that we need to be very agile to respond quickly and take hold of opportunities when they arise and be on the lookout for new things.

What are you working on now, and what do you plan to do in the next few months?

GS: Currently we’re working on the design, modelling and optimization of semiconductor quantum-dot-based single photon sources embedded in optical cavities. We are aiming to exploit cavity quantum electrodynamics and coherent phenomena to produce high-quality single-photon sources. We also hope to describe a wider range of quantum systems, such as spins in silicon, defects in 2D materials, or nitrogen-vacancy centres in nanodiamonds embedded in photonic structures. We’re interested in waveguide geometries with couplers, platers, rotors, Mach–Zehnder interferometers and different types of optical cavities such as photonic crystals, micro-resonators, and others. 

But our long-term plans are to tackle the problem of generating multi-photon entangled states, which are needed for realizing a quantum computer. We want to optimize these multi-photon entangled sources from the point of view of both geometry and quantum system properties.

There are a lot of different ways of making qubits, and you mentioned many of them just now. I guess being qubit-neutral must be one of the advantages of being a quantum software company rather than a hardware company.

GS: Yes, but we are focusing on the photonic quantum computing platform because we strongly believe that the future of quantum computing lies in integrated quantum photonics on a chip. This is the way that we can produce scalable architectures; it’s a natural way and it has worked already in electronics, so we need to take that into account. We’re much more likely to achieve large-scale integration using mature, semiconducting technologies.

MK: Our software is also applicable to neutral atoms, so companies like ColdQuanta that are building quantum computers from neutral atoms are also of interest to us, and we have very ambitious plans to develop our software suite so that we can really make a difference in the various sub-sectors of the quantum technology industry. But that’s further along our roadmap, and Gaby’s right that we are focusing on the photonic modality for the physical implementation of qubits, because it’s not well-addressed so far. We’re trying to rectify that and make sure that we can really develop those systems properly and address our customers’ needs in an appropriate manner so that they are happy with the service they get from us.

Mirella Koleva is the chief executive officer and Gaby Slavcheva is the chief scientific officer at Quantopticon.