IBM quantum processor hits 19-second benchmark as Kyoto team cracks W state measurement

The result, posted to arXiv, was led by Tigran Sedrakyan, a theoretical condensed matter physicist at BlueQubit. His team used IBM's Nighthawk r2, a 120-qubit superconducting processor available through the company's cloud platform. They selected 61 qubits and ran random circuits of up to 40 cycles. A workload of 36 cycles and 918 two-qubit gates produced one million samples in 19 seconds.

The claim rests on tensor-network contraction, a classical technique for estimating the computational cost of a simulation. The researchers calculated 1.2 × 10²⁷ operations, translating that into roughly 110 years on Frontier, the first exascale supercomputer.

Caveats and a second result

That 110-year figure is not a fundamental speed limit. It is an estimate for one method of reproducing the experiment, and classical researchers have repeatedly found shortcuts. The preprint authors acknowledge this directly, noting that they do not claim no classical computer will ever match the task.

ScienceAlert reported the work on 29 September. The same day, ScienceDaily carried a Kyoto University result on a different quantum problem: measuring W states, a form of multi-photon entanglement that had resisted an efficient one-shot measurement for more than 25 years.

"More than 25 years after the initial proposal concerning the entangled measurement for GHZ states, we have finally obtained the entangled measurement for the W state as well, with genuine experimental demonstration for 3-photon W states," said corresponding author Shigeki Takeuchi, quoted by ScienceDaily.

The Kyoto and Hiroshima University team built a photonic quantum circuit that performs a quantum Fourier transformation, exploiting a property called cyclic shift symmetry. They tested it with three photons and measured fidelity, the probability the device returns the correct result for a pure W-state input. The method could feed into quantum teleportation, communication protocols and measurement-based quantum computing, though nothing here is a product.

Security work runs in parallel

Cloudflare used its Birthday Week to publish a mitigation for a different quantum risk: downgrade attacks on IPsec. The company said it worked with the IETF on an extension that prevents an attacker from making post-quantum-capable endpoints fall back to classical cryptography. Beta support is available in Cloudflare WAN and Magic Transit via an account flag.

Cloudflare's post notes the attack requires a quantum computation during the protocol handshake, not the offline harvest-now, decrypt-later pattern. It also says resource estimates for quantum attacks on public key cryptography have fallen, prompting the company to move its transition deadline to 2029.

Elsewhere, the money and hardware keep moving. Efficient Computer said it raised a $97 million Series B led by TQ Ventures, bringing its total to $173 million at a $650 million valuation, and claimed 10 to 100 times better energy efficiency than traditional CPU architectures. The company says it is launching its Electron E1 at volume for embedded physical AI systems.

And on 25 September, at the Global Digital Trade Expo, Chinese commercial space firm STAR.VISION Aerospace unveiled a space-based computing constellation called Space.IDC, according to China in Space. The plan covers about 1,080 spacecraft by 2035, split between inference and general compute, with three designs ranging from 40 to 60 PetaFLOPs up to 460 to 1000 PetaFLOPs. STAR.VISION said it secured 10 billion Yuan, about 1.49 billion US dollars as of 28 September, in credit agreements with the Industrial and Commercial Bank of China and the Agricultural Bank of China. Orbital details, inter-satellite links and regulatory filings were not shared.