Scientists have demonstrated that a photonic qubit — a quantum bit powered by a particle of light — can detect and correct its own errors while running at room temperature. They say it is a foundational step toward scalable quantum processors.
In a new study published June 4 in the journal Nature, researchers at Canadian quantum computing startup Xanadu created a so-called “Gottesman–Kitaev–Preskill” (GKP) state directly on a silicon chip.
GKP states are a type of quantum state that spreads information across multiple photons in a pattern that enables small errors to be spotted and corrected. This means that each qubit is capable of correcting itself, without needing to be bundled into large arrays of redundant qubits — a common requirement in today’s error-correction methods.
It marks the first time this type of error-resistant quantum state has been generated using a process compatible with conventional chip manufacturing, the scientists said.
The breakthrough suggests that error-correcting quantum states could be produced with the same tools used to manufacture conventional computer chips — bringing reliable, room-temperature quantum hardware a step closer to reality.
The qubit-cooling conundrum
Quantum computers work very differently from the classical machines we use today. Classical computers store information in binary bits, represented as either 1s or 0s. Quantum systems, meanwhile, use qubits that can exist in a “superposition” of both states. This enables them to solve complex calculations in parallel, and they can one day perform far beyond the reach of conventional systems.
But qubits are notoriously fragile. Even the smallest fluctuations in temperature, electromagnetic radiation or environmental noise can disrupt a qubit’s state and corrupt its data.
To guard against this, many quantum systems operate at temperatures close to absolute zero (minus 459.67 degrees Fahrenheit or minus 273.15 degrees Celsius) using complex cooling systems to maintain “coherence” — the fragile quantum connection through which qubits perform calculations.
Related: Coldest-ever qubits could lead to faster quantum computers
While this cooling helps preserve quantum information, it also makes quantum computers bulky, expensive and impractical to scale. Xanadu’s solution seeks to address this by using photons — particles of light that don’t require deep cooling — to build qubits that run on silicon chips at room temperature.
The team’s GKP demonstration tackles another key challenge: quantum error correction. Most quantum systems today rely on groupings of multiple physical qubits that work together to detect and fix errors, known as a “logical qubit.” Xanadu’s photonic qubit sidesteps this by handling correction within each individual qubit, simplifying the hardware and paving the way for more scalable designs.
“GKP states are, in a sense, the optimal photonic qubit, since they enable logic gates and error correction at room temperature and using relatively straightforward, deterministic operations,” Zachary Vernon, CTO of hardware at Xanadu, said in a statement.
“This demonstration is an important empirical milestone showing our recent successes in loss reduction and performance improvement across chip fabrication, component design and detector efficiency.”
The result builds on Xanadu’s earlier development of Aurora, a modular quantum computing platform that connects multiple photonic chips using optical fiber. While Aurora addressed the challenge of scaling across a network, this new chip focuses on making each qubit more robust — a critical requirement for building fault-tolerant systems.
Xanadu representatives said the next challenge was reducing optical loss, which happens when photons are scattered or absorbed as they travel through the chip’s components.