Fewer qubits and better error correction: Nord Quantique's multimode encoding breakthrough

(Press-News.org) SHERBROOKE, Canada (May 29, 2025) – Nord Quantique, a pioneer in the field of quantum error correction, today announces a first in applied physics. The company has successfully developed bosonic qubit technology with multimode encoding, which outlines a path to a major reduction in the number of qubits required for quantum error correction (QEC). The result is an approach to quantum computing which will deliver smaller yet more powerful systems that consume a fraction of the energy. These smaller systems are also simpler to develop to utility-scale due to their size and lower requirements for cryogenics and control electronics.

To carry out this demonstration, the company has implemented an advanced bosonic code known as Tesseract code. This provides the system protection against many common types of errors including bit flips, phase flips, as well as control errors.  Another key advantage over single-mode encoding is that leakage errors, which remove the qubit from the encoding space, can now be detected.

In this demonstration, post-selection was used to filter out imperfect runs, and 12.6% of the data was discarded each round. This showed excellent stability in the quantum information, and no measurable decay through 32 error correction cycles. The Tesseract code allows for increased error detection, and it is expected that this will translate into additional QEC benefits as more modes are added. These results are therefore a key stepping stone in the development of Nord Quantique’s hardware efficient approach.

“The amount of physical qubits dedicated to quantum error correction has always presented a major challenge for our industry. Using physical qubits to create redundancy makes the system large, inefficient and complex, which also increases energy requirements” said Julien Camirand-Lemyre, CEO of Nord Quantique. “Multimode encoding allows us to build quantum computers with excellent error correction capabilities, but without the impediment of all those physical qubits. Beyond their smaller and more practical size, our machines will also consume a fraction of the energy, which makes them appealing for instance to HPC centers where energy costs are top of mind.”

The core concept of the multimode approach centers on simultaneously using multiple quantum modes to encode individual qubits. Each mode represents a different resonance frequency inside an aluminum cavity and offers additional redundancy, which protects quantum information. The number of photons populating each mode can also be increased for even more protection, further escalating QEC capabilities. This breakthrough now allows additional error correction capacity and extra means for detecting errors, while keeping the number of qubits static. As these systems scale up, this can lead to what amounts to a 1:1 ratio of physical cavities to logical qubits. In this way, multimode encoding represents a path toward higher performing QEC without increasing the size of the system.

This encoding strategy also delivers more benefits which compound as they scale, opening new avenues for fault-tolerant quantum computing. Examples include a reduction in the impact of auxiliary decay errors, enhancing logical lifetimes through suppression of silent errors, and extraction of confidence information used for further improving error detection and correction strategies.

From an efficiency standpoint, a Nord Quantique quantum computer with 1,000+ logical qubits would take up about 20 square meters, compact enough to integrate inside a data center. From an expense standpoint, these systems drive a major reduction of energy consumption. While the amounts fluctuate depending on the computation, using the example of RSA-830, we project solving the problem in an hour at a speed of 1 MHz, consuming 120 kWh. Estimates have those numbers at 1,300 kW over 9 days using classical HPC – consuming 280,000 kWh. The estimates also compare favorably against alternate approaches in quantum computing (Nord Quantique’s business case with specific figures on speed, emissions and energy consumption is available upon request).

“After years working on developing multimode operations on states encoded in superconducting cavities, I am pleased to see the progress made by the team at Nord Quantique,” added Yvonne Gao, Assistant Professor at the National University of Singapore and Principal Investigator at the Centre for Quantum Technologies. “Their approach of encoding logical qubits in multimode Tesseract states is a very effective method of addressing error correction and I am impressed with these results. They are an important step forward on the industry’s journey toward utility-scale quantum computing.” 

Through this scientific advance, Nord Quantique now has a clear path to delivering fault-tolerance at utility-scale. The team will continue to improve its results by leveraging systems with additional modes to push the boundaries of quantum error correction. The company’s first utility-scale quantum computers with more than a hundred logical qubits are expected by 2029.


About Nord Quantique

Founded in 2020 in Sherbrooke, Quebec – Canada’s leading quantum hub, Nord Quantique is committed to overcoming the challenge of quantum error correction, today’s principal barrier to fault-tolerant quantum computing. The company has demonstrated its highly scalable multimode technology using Tesseract codes, another first in the race to deliver useful quantum computing. By building error correction directly into each individual qubit and through the application of bosonic codes, Nord Quantique expects to reach fault tolerance sooner. Few errors combined with fast calculation speeds means the company will be able to deliver useful quantum computers without millions of qubits. For additional insight into our pioneering work, please visit our website.

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