Hefei Sizhen Chip Technology, working with researchers from the University of Science and Technology of China, demonstrated on-chip generation of a 4-photon, 16-qubit GHZ state and a single-photon, 4-qubit cluster state on a self-developed programmable silicon photonic chip, verifying genuine entanglement across 10 qubits through entanglement witnessing. The company describes it as the largest entangled state demonstrated on an optical quantum chip to date, and the work is currently posted as an arXiv preprint rather than a peer-reviewed publication.
The approach: measurement-based, not gate-based
Sizhen Chip's architecture uses measurement-based quantum computing (MBQC), an approach that builds a large entangled resource state up front, then drives the actual computation through a sequence of single-qubit measurements rather than applying gates directly to qubits in sequence. The chip encodes qubits using the high-dimensional path degrees of freedom of single photons, and a four-layer programmable measurement module handles both preparing the multi-qubit graph states and executing the measurements that turn that resource into a computation.
What the numbers show
Sixteen qubits from four photons works because each photon carries multiple qubits of information through its path encoding, not because sixteen separate photons were entangled. The company's own claim to watch for independent replication is the entanglement witnessing result: genuine, verified entanglement across 10 qubits, a smaller but more rigorously checkable number than the 16-qubit graph state figure headline number. As a demonstration of the architecture's usefulness for computation rather than entanglement generation alone, the team ran Grover's search algorithm on a 4-qubit cluster state and reported a 0.987 average identification probability, a real, specific benchmark number rather than a qualitative claim.
A preprint, not a peer-reviewed result
This work is posted to arXiv under the title "On-chip generation of multi-qubit graph states with high-dimensional encoded single photons" and hasn't gone through peer review at the time of this writing. That doesn't make the result wrong, but it does mean the numbers above haven't yet had independent scrutiny applied to them, worth keeping in mind before treating "largest entangled state on an optical chip to date" as a settled record rather than a company's own characterization of its result.
Part of a broader Chinese photonic quantum push
Sizhen Chip calls itself the first domestic optical quantum computing company to achieve large-scale graph state construction on-chip, and frames the result as evidence that a million-qubit optical quantum computer is feasible. That framing lands alongside TuringQ's move toward a Shanghai STAR Market listing, another photonic quantum company pursuing commercialization in China. Photonic architecture is a genuinely active area of Chinese quantum investment right now, not a single company's isolated bet.
What to watch next
Peer review of the arXiv preprint is the near-term checkpoint. Past that, the number worth tracking is whether Sizhen Chip's four-layer measurement module scales to more photons and higher path-encoding dimensions without the entanglement fidelity dropping, since that's the actual bottleneck standing between a 16-qubit demonstration and the million-qubit claim the company is making about where this leads.