Insider Brief
- Xanadu has demonstrated the on-chip generation of GKP states — error-resistant photonic qubits — marking a milestone toward scalable, fault-tolerant quantum computing.
- The experiment used silicon nitride waveguides, custom detectors with over 99% efficiency, and loss-optimized packaging to produce and verify complex quantum states suited for room-temperature operation.
- While optical loss remains a limiting factor, the result lays the foundation for modular, fiber-compatible quantum systems and pushes photonic platforms closer to utility-scale performance.
Xanadu has taken a key step toward scalable fault-tolerant quantum computing by demonstrating the generation of error-resistant photonic qubits — known as GKP states — on a silicon-based chip platform, a first-of-its-kind achievement now published in Nature.
The milestone positions the Toronto-based quantum startup closer to building a modular and networked photonic quantum computer, a device that uses photons, rather than electrons, to perform calculations, according to the paper and a company statement. By encoding quantum information into complex photon states that can withstand noise and loss, the work directly addresses one of the central obstacles to quantum scalability: preserving fragile quantum data as systems grow in size and complexity.
“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 the 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.”
Making Photons Resilient
Photons, the fundamental particles of light, are naturally suited for quantum information processing. They travel fast, resist environmental interference and can be routed through fiber networks. But using them as qubits has been limited by their tendency to be lost in optical components or miscounted during detection.
To overcome this, Xanadu’s researchers generated what are known as Gottesman–Kitaev–Preskill (GKP) states — structured quantum states made of many photons arranged in specific superpositions. These states encode information in a way that makes it possible to detect and correct small errors, such as phase shifts or photon loss, using well-known quantum error correction techniques.
GKP states have long been considered a foundational element for continuous-variable quantum computing architectures. Until now, however, generating them with sufficient quality on an integrated platform remained out of reach.
Built for Scalability
Xanadu’s experiment demonstrates that GKP states can be produced directly on-chip using integrated photonics, paving the way for scalable manufacturing. The system is based on silicon nitride waveguides fabricated on 300 mm wafers, a format common in commercial semiconductor manufacturing. These waveguides exhibit extremely low optical losses, a critical requirement for preserving quantum coherence over time.
In addition to the waveguide platform, the setup included photon-number-resolving detectors with over 99% efficiency, developed in-house by Xanadu. These detectors can distinguish between one photon and many, a capability essential for preparing and verifying complex photonic states like GKP.
Optical packaging was also a major focus of the experiment. High-precision alignment, custom chip mounts, and loss-optimized fiber connections ensured that the quantum states could be routed and measured without degrading the delicate information they carried.
Together, these components form the foundation of a photonic quantum computing stack that is both modular and fiber-compatible. These are qualities that are crucial for building large-scale, distributed quantum processors.
Why GKP States Matter
GKP states are sometimes described, as Vernon mentions, as the “ideal photonic qubit” because they allow quantum logic operations and error correction to be implemented at room temperature using deterministic, optical methods. Unlike probabilistic entanglement schemes, which require repeated attempts and feed-forward control, GKP states support fault-tolerant computing through relatively straightforward linear optics and measurement routines.
It’s important to note that GKP states also integrate seamlessly into hybrid architectures. For example, they can serve as building blocks for quantum networks that connect separate chips or modules, or they can be fused into larger cluster states suitable for measurement-based computing. Their compatibility with optical fiber means they can be distributed across systems or even across datacenters.
The demonstration could, then, mark a turning point for photonic quantum computing because it brings systems closer to the error thresholds needed for utility-scale quantum machines. While superconducting and trapped-ion platforms have made strides toward fault tolerance, Xanadu’s approach offers a fundamentally different route — one that photonic QC firms hope will ultimately prove more compatible with telecom infrastructure and room-temperature operation.
Limitations and Upcoming Goals
While the result is significant, the team indicates that the quality of current GKP states still falls short of the thresholds needed for full fault-tolerant operation. The dominant limiting factor remains optical loss, which reduces the purity and coherence of the quantum states.
Improving chip fabrication, optimizing waveguide geometry and refining packaging processes will be ongoing efforts aimed at pushing fidelity higher. The company is also exploring error mitigation techniques that can compensate for known sources of loss or imperfection, as well as hardware-level innovations that can boost photon generation and detection rates.
Further ahead, Xanadu plans to combine its GKP generation techniques with logic gates, error correction protocols, and networking capabilities demonstrated in its Aurora system — an earlier milestone in which the company showed all major components of a scalable photonic architecture operating together.
Xanadu’s latest work also offers a look at how the company is solidifying its commitment to a modular vision of quantum computing: instead of building ever-larger monolithic machines.
This vision is uniquely aligned with photonic systems, where the data carriers — photons — naturally travel between modules without introducing significant error. The successful demonstration of on-chip GKP states brings this vision into sharper focus, showing a path to commercialization where essential error-correcting elements can be mass-produced, manipulated and measured within a scalable, semiconductor-compatible platform.
