A milestone in quantum error correction

With a background of 15 years in quantum science, Camirand Lemyre had the expertise to co-found the company in 2020, after it was spun out from the Institut Quantique at the Université de Sherbrooke in Quebec, Canada.

When posed the question of how mature he thought quantum computing was, Camirand Lemyre said this was a question he received a lot, acknowledging that going back 15 years, quantum computing “wasn’t a thing at all”.

“But this is something that people were researching, trying to find [the] best approaches to scale this technology [and] understand if it was possible to scale or not,” he said. “And in the last 15 years, I think this is one of the questions that the industry has been very good at answering: we can build a large system composed of these qubits, which are the classical equivalent of the transistor.” 

And the field is only expected to grow, with serious money being poured into the technology. Earlier this month, IonQ announced the acquisition of Oxford Ionics for $1.075 billion - the largest deal of its kind to date.

Quantum error correction

In spite of this maturity, the hardware continues to experience errors. Quantum error correction relates to a set of techniques designed to protect information from errors caused by ‘noise’ in quantum computers, although these techniques can vary depending on the company’s objective. Some may be more effective than others.

Recognising that this would be a problem - and perhaps only be exacerbated as time went on - Nord Quantique was founded to focus on quantum error correction.

Performing quantum error correction in a computer requires redundancy - a way to recover from errors, as they occur. A common approach to try and tackle these errors is to increase the number of physical qubits and scale up the size of the computer. However, this is not a guarantee that this will resolve error correction. . Up to 1,000 physical qubits can be required for one logical qubit, which are used as a redundancy to protect quantum information as error correction.

“Most advanced quantum systems have around hundreds to thousands of qubits,” said Camirand Lemyre. “So we’ll need systems that have a million more qubits to be useful if we’re following this approach. And this is exactly what we’re challenging at Nord Quantique.”

Adopting a different approach - designing a system that doesn’t need all of these physical qubits to operate - the company is building a system, the multi-mode system, that can perform error correction with one logical qubit, as well as using a bosonic code, Tesseract code, to provide the system protection against several common types of errors. Fundamentally, this means the quantum computer doesn’t need to be increased in size to reduce errors.

The prototype the company has built is made up of micro resonators; pieces of super connected circuits.

“What you see … is a superconducting cavity, it’s cooled down at a low temperature, at 10 millikelvin, and at those temperatures, what we can do … is trap microwave photons. We host these microwave photons and we can have multiple of them inside the cavity.

“The idea is to use the fact that we have a lot of those … to build a qubit that has this error correction property.” In other words, the redundancy is built into the logical qubit Nord Quantique is using for error correction.

This prototype builds on the foundations of the company’s earlier work, which has been going on since its founding in 2020.

“To produce a qubit that produces fewer errors with quantum error correction … that was one of the biggest achievements of Nord Quantique,” said Camirand Lemyre. “At the end of the day, you also need high performance quantum error correction. We knew that the previous system that we had, had some flaws.” 

The plan going forward is to commercialise some of these prototypes, which prove very attractive for companies that want “error correction off the shelf”.

Implications of smaller quantum computers

Reducing the size of a quantum computer is serious business, because it means the space requirements on data centres are less pressured. That also translates to reduced energy consumption and subsequently reduced costs. Energy consumption can fluctuate depending on the computation, but Nord Quantique estimates that with its technology it can cut power consumption by approximately 90% compared with existing data centres, due to the speed of computation, the reduced size, and fewer electronic components. to less cost, and reduced energy consumption, the latter of which is a major concern[SL3] . 

“What we want to build, at Nord Quantique, is [a] data centre full of quantum computers, not [just] a single one,” said Camirand Lemyre. “It’s in this vision also that we think size is important.” 

Given that quantum computing is showing no signs of slowing down, the company’s approach indicates a future-proofing mindset where the reduced size of quantum computers opens up possibilities for more computers and computational power.

“The important thing here is … the vision that we’re bringing forward is … different in the industry,” said Camirand Lemyre. “A lot of the push since the early days has been on improving the qubit count and making this the sole metric for success.

“Hardware efficiency is … reducing the overheads for error correction is important in quantum and Nord Quantique is pushing this way, and we’re taking a bold approach to this.”