Quantum Bridge: Shaping the Future of Quantum Cybersecurity

The dawn of quantum computing is both a marvel and a menace.?

On the one hand, it promises to revolutionize how we process information; on the other, it threatens the very encryption systems that safeguard the internet today.

Preparing for this quantum future means upgrading classical encryption standards to be quantum-safe. At the same time, quantum technology offers a chance to create entirely new encryption paradigms.

Quantum Bridge, founded in 2019 by Mattia Montagna and Hoi-Kwong Lo as a spin-out from the University of Toronto, pioneers quantum-safe communications with a suite of products and services. Their Distributed Symmetric Key Establishment (DSKE) technology integrates classical cryptographic techniques with quantum-safe algorithms, safeguarding networks already today. At the same time, they’re developing quantum repeaters, the building blocks needed to build a secure and quantum-native internet.

Learn more about the future of quantum cybersecurity from our interview with the co-founder and CEO, Mattia Montagna:?

Why Did You Start Quantum Bridge?

My background is in physics—I have always been passionate about physics, and even my parents were physicists. I completed my Bachelor’s and Master’s in physics, did a PhD in econophysics, and then worked with major financial institutions, including the European Central Bank.

At the same time, I always wanted to become an entrepreneur and build a team working on a project that could change the world. When I decided to explore a new path beyond finance, I went back to physics and got very passionate about quantum cryptography and the cybersecurity world. For me personally and the cybersecurity market, quantum computing presents a turning point. I wanted to be part of that story, so I decided to found Quantum Bridge.?

What’s the Threat of Quantum Computers to Cryptography?

Many widely used cryptographic algorithms are based on hard mathematical problems such as number factorization: While it’s relatively easy to multiply prime numbers to get a result, especially for large numbers, it’s computationally very expensive for classical computers to find the prime numbers when these are sufficiently large. This principle is what many widely used cryptography algorithms use to encrypt data, but these are only safe so long as it’s hard to find prime factors.

Yet, one of the cornerstones of quantum computing has been the discovery of Shor’s algorithm, which allows quantum computers to factor numbers efficiently. Encryption methods that we think are safe today because it would take even the best supercomputers in the world millennia to crack them might be cracked by a quantum computer within minutes or seconds. Quantum computers are still very early, and no one knows exactly when they’ll be powerful enough to break these algorithms, but we’ll need to prepare for it today.?

There are two ways to deal with it, and we’re working on implementing both of them: either upgrade classical encryption systems to use algorithms that are resistant to quantum attacks or implement quantum networks and use the fundamental laws of quantum mechanics to encrypt data. As quantum technology is still very early, it will take many years to build quantum networks and, eventually, the quantum internet.?

What Does Quantum Bridge Do?

Quantum Bridge is like a bridge between the classical and quantum worlds. Our company has two departments, one of which is already building classical cryptography to protect networks against quantum attacks before they threaten national security and critical infrastructure. It’s why we’re developing the tools to upgrade existing cryptography systems to become quantum-safe, and most of our resources are going there—this is the commercial side of the startup.

On the other hand, we’re also building quantum repeaters, the components needed to build quantum networks, in collaboration with the Canadian government—the moonshot side of our startup.

There’s a fascinating quantum effect called entanglement, in which entangled particles, such as two photons, remain correlated no matter the distance between them. If you make a measurement on one, what you do is reflected on the second one and vice versa. It is a powerful effect and one of the reasons why quantum computers and quantum networks have fundamentally different capabilities from their classical counterparts.?

The difficult part is not producing entangled photons but sending them to the other side of the world. Due to fiber losses, you always lose photons, as some of them get absorbed. Sending and detecting photons over long distances is tricky, and I’ll explain below how we’re building quantum repeaters to distribute and entangle photons over long distances.?

How Do You Upgrade Classical Cryptography?

First, on the classical cryptography side, we provide a key management solution, so-called Distributed Symmetric Key Establishment (DSKE) technology, that can be integrated into existing network appliances. We don’t encrypt the actual network traffic, but it provides keys to layers one, two and three in cryptography.

We work with cryptography authorities to make this paradigm shift from current cryptography standards to quantum-secure ones. It’s like moving from pure mathematics to physics. With quantum computing, the surface for attacks on a network becomes much larger, and there will be completely different attacks unknown today to cryptographic authorities.?

This big shift won’t happen instantly, but over the next three to five years, and for us as a company, it’s an opportunity to deliver value today, not just in five years.?

Why Do We Need To Upgrade Now?

The transition is difficult because cryptography is ubiquitous in our current infrastructure, and it is typically not designed to be agile and upgradeable.?

You need a detailed understanding of what people are using today and where. And which certification authority is responsible. There’s a lot of cryptography beneath everything you do, from online shopping to sending encrypted chat messages, and it’s a tough job to understand all of this—it doesn’t happen quickly nor in isolation.

Understanding and navigating this landscape is tricky but provides organizations with a lot of value as cryptography authorities have publicly stated that they want to migrate fully to quantum-resistant algorithms by 2030.?

This timeline is not determined by when quantum computers will be able to break cryptography but to follow a zero-risk approach and avoid sensitive data being stored and decrypted once quantum computers are powerful enough.?

The question about when to migrate does not depend on quantum development, but the answer should be clear: as soon as possible. Governments have realized the threat and are already making efforts to migrate. However, this applies not just to government systems and documents from the defense departments but also to infrastructure like the power grid.?

In addition, data protection policies can require long timelines for keeping data confidential. To be compliant, you need to upgrade now.?

How Do Your Quantum Repeaters Work?

Quantum repeaters are essential building blocks for quantum networks and allow entanglement to be distributed across large distances.?

You can't send a photon directly from point A to point B over thousands of kilometers—there’s a very high chance it will get lost. Instead, the distance is divided into smaller intervals, such as 20 kilometers. At each interval, a photon source generates pairs of entangled photons, sending one to the left and one to the right. When these photons reach intermediary nodes along the network, entanglement swapping occurs—while the two photons arriving at the intermediary node get absorbed, the two photons at the outer nodes get entangled.

Every node in the chain must successfully swap entanglement for the entire chain to succeed and to entangle the two outermost photons, which can then be thousands of kilometers apart. Quantum repeaters at the intermediary nodes use quantum memories to buffer photons to help with entanglement swapping. However, entanglement swapping is inherently probabilistic, with a failure rate often exceeding 50% when using linear optical components.?

You need to wait for all nodes to succeed in swapping the entanglement, so it takes a lot of time. Current quantum repeaters allow for only very limited quantum networks, including limited range (typically under 100 kilometers), low success rates, and high costs.

We’re trying to build an all-photonic quantum repeater, avoiding quantum memories and lifting those limitations to build truly long-range quantum networks.?

Instead of sending single photons to a middle node, we send a lot of photons that are all fully entangled already from the start. At the middle node, our quantum repeater swaps a larger number of photons, all entangled with each other in a so-called repeater cluster state. This makes it very likely that at least one photon gets swapped, thus ensuring a higher probability of establishing a connection between the outermost nodes. So, we’re moving the problem from building quantum memories to creating the cluster states.

A major advantage of using these quantum repeaters to build quantum networks, over, for example, just doing quantum key distribution QKD, is that you never convert quantum information back to classical information. You don’t have to trust the middle quantum repeater nodes.?

The second advantage is that quantum repeaters are not just a point solution; they’re a tool to build an entire network. So you can share the costs of building infrastructure for quantum networks among many users who are incentivized to build the quantum network, eventually even a quantum internet.?

What’s Your Progress With Quantum Bridge?

As the technology for building our quantum repeaters is still very early, we’re focused on building a commercial product for classical cryptography. Our approach for the quantum repeater is to get all the fundamental physics right, relying on government grants to make sure all the major roadblocks are figured out before raising a lot of money.?

For the quantum repeater, we have two small teams, one working on theory and one experimental. The theory team is trying to optimize what the experimental team is doing. Together, they aim to figure out how to build scalable quantum networks. The experimental team is creating the building blocks, e.g., a generator for the deterministic cluster states, so they’re high-quality and able to create identical cluster states.?

We’re also exploring photonic quantum computing, so we’ll be doing more than quantum communications in the future. Building quantum repeaters is our background, and we have decades of experience in this area, but there’s no significant difference between building quantum repeaters and using our cluster state generator for quantum computing.?

There will be many synergies between classical and quantum cryptography in the future, especially since the same customers will procure them. So, we’re establishing these relationships today, and we continue to work on our quantum repeaters, which will allow quantum links to become part of our infrastructure in the future.?

What Advice Would You Give Fellow Deep Tech Founders??

Initially, we spent a lot of time developing the technology, and thinking about the product and the roadmap, but not enough time talking to customers. Over time, we learned how important it is to spend a lot of time with your customers and understand their needs.?

Deep tech founders, especially technical ones, often make the mistake of building a product in isolation, removed from the customer’s world. But they need to be absolutely customer-centric.?

You must understand your customers' timelines, as large government and enterprise customers move notoriously slowly. In a large organization, find a department where your solutions fit, figure out how you can help them succeed, and convince them that they need to innovate and deliver value. Then, move on to other parts of the organization but respect their timeline. Plan accordingly, as things may take time.?

Timing a market is crazy hard. Everyone always wants to buy at the bottom and sell at the peak, but consistently doing so is very hard. When you start a business too early, you risk running out of money before the market is ripe for your solution. If you’re starting out too late, many other companies have captured market share, and it will be hard to enter.?

Picking the right timing is difficult, but thankfully, there’s a relatively long window of opportunity for quantum cryptography, at least five years. You can start your company in a market niche and then expand from there.?

I came from an established career in finance. Jumping from there to entrepreneurship is hard. You lose a lot of security in working with a massive organization and many perks and benefits. You’re moving from always having a surplus of resources to counting every dollar and minute for your startup. It also makes a big difference whether you’re coming from academia.?

Timing in the quantum market is tricky, but I think now is a good time to start. There are many dimensions to consider, but there is currently a lot of interest in the industry and many opportunities to create and capture value.?

Finally, you have to be obsessed with what you’re doing to succeed!?