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30 May 2024
Development using silicon photonics is said to satisfy the first requirement of long-distance quantum communication.
Photonic, the Canadian startup company working to develop quantum computing and networking technology based on optically linked silicon qubits, says it has now demonstrated entanglement between two modules separated by a distance of 40 meters.
In work with key collaborator and investor Microsoft the firm claims to have made a significant breakthrough, by confirming remote entanglement between two so-called “T-centers”, the light-emitting defects in silicon previously described by Photonic’s founder Stephanie Simmons as the “missing component” needed to unlock the first credible path to commercial quantum computing.
‘Teleported’ gate
“Large-scale quantum algorithms running across multiple quantum computers require enormous amounts of distributed entanglement to work well,” explained Simmons in a release announcing the latest work.
“These demonstrations highlight the promise of our distinctive architectural approach to solve the challenge of scaling beyond single nodes. While there is still much work ahead, it’s important to acknowledge the pivotal role that entanglement distribution must play in shaping quantum system designs.”
In a separate blog post detailing the breakthrough Dennis Tom, general manager of Microsoft’s Azure Quantum business, added:
“Photonic executed a teleported CNOT gate between physically separated silicon spin qubits, thus satisfying the first requirement of long-distance quantum communication.”
Tom wrote that the accomplishment indicated the capability to operate a quantum computer in an industrial setting by using teleportation to execute logic gates between qubits in different locations - in this case the silicon spin qubits were housed in separate cryostats, connected by a 40 m-long fiber-optic cable.
“Entanglement between qubits that are not connected physically, or even located in the same cryostat, paves the way for long-distance communication between quantum computers and is one means to accomplish scaled quantum computing,” he pointed out.
Fiber connections
In a related white paper authored by Photonic, the team presents its preliminary demonstrations of distributed quantum computing protocols using T-centers in isotopically-enriched silicon - in other words, point defects in the silicon crystal lattice that emit at telecom wavelengths.
“These entangled qubits are on silicon photonic chips, each capable of hosting and controlling thousands of qubits,” they claim in the paper’s conclusion. “These qubits can be connected via optical fibers, making their operation compatible with optical fiber switch networks.
“This result unlocks distributed quantum computing in silicon, and a path towards networks of silicon quantum processors performing commercially and socially transformative calculations.”
Established by Simon Fraser University researchers Simmons and Michael Thewalt back in 2016, Photonic raised $100 million in a November 2023 venture round featuring Microsoft and others.
Hermann Hauser, the co-founder of investor Amadeus Capital Partners, said at the time:
“Photonic is solving one of the central challenges for scalable quantum computing. By linking qubits with photons on a silicon-based architecture, the power of quantum processing can be unleashed across a distributed computing network with confidence that error correction is able to keep pace. This is an innovation with awesome potential.”
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