Harvard Team Builds First Continuously Operating Quantum Computer

Researchers at Harvard University and MIT have unveiled a 3,000-qubit quantum computing system capable of running continuously for more than two hours, a significant breakthrough that overcomes a major obstacle to building large-scale, fault-tolerant quantum computers.

Published in the journal Nature, the findings address the problem of “atom loss,” a phenomenon where quantum bits (qubits) are lost due to environmental noise, forcing traditional systems to constantly restart. By creating a continuous process to replace lost atoms in real-time, the team’s new architecture moves quantum machines from being momentary experiments to potentially sustained, practical devices.

The team’s ingenious solution combines an optical lattice conveyor belt and optical tweezers to maintain system integrity. The conveyor system continuously replenishes lost atoms in a large-scale array, a process that can inject up to 300,000 atoms per second. This speed is fast enough to outpace atom loss and maintain quantum information coherence.

“There’s now fundamentally nothing limiting how long our usual atom and quantum computers can run for,” said Tout T. Wang, a research associate who works in the lab that designed the machine. “Even if atoms get lost with a small probability, we can bring fresh atoms in to replace them and not affect the quantum information being stored in the system.”

For cryptography, this new capability has significant security implications. Many existing and post-quantum cryptographic schemes are designed under the assumption that quantum computers will have limited, short run times.

Senior author Professor Mikhail Lukin believes the path forward is clearer than ever.

“One can really see a very direct path towards realizing it,” he said, envisioning future quantum systems that could run for days.

One of the major challenges facing quantum computing today is keeping these machines up and running without interruption. At the heart of quantum computing lies the qubit, which is made up of subatomic particles.

However, when these quantum computers are in operation, qubits can sometimes escape the system due to a phenomenon known as “atom loss.” This leads to a loss of information and can ultimately cause the machines to fail.