Jiuzhang 4.0 Photonic Quantum Computer Solves Boson Sampling

Researchers at the University of Science and Technology of China built a photonic quantum computer called Jiuzhang 4.0 that manipulated 3,050 photons and completed a boson sampling task in 25 microseconds. The team reported a source efficiency of 92% and an overall system efficiency of 51%. They estimated a top classical supercomputer would need more than 10^42 years to perform the same calculation for this task.

Jiuzhang 4.0 follows earlier photon-based systems from the same group. The previous publicly reported device handled 255 photons in 2023. The team said improvements include a specially designed optical light source and a redesigned interferometer that reduced photon loss and raised the proportion of photons reaching the detectors.

Lu Chaoyang, a USTC professor, noted that “the most complex data sample generated by ‘Jiuzhang 4.0’ takes only 25 microseconds to produce — shorter than the blink of an eye.” He described the timing and efficiency gains as enabling experiments at scales that were previously out of reach for photonic setups and suggested the methods could support construction of “trillion-qubit-mode three-dimensional cluster states.”

Boson sampling is a targeted computation in which many photons pass through an optical network and are measured to sample a probability distribution. It is not a general-purpose quantum algorithm, but it is used as a benchmark to test computational tasks that are hard for classical machines. The estimate that a classical supercomputer would require more than 10^42 years applies to this specific boson sampling task under current classical algorithms and hardware.

The research paper and accompanying materials highlight photon loss as a key limitation for photonic quantum computing. Increasing the fraction of produced photons that travel through the interferometer and reach detectors improves sampling fidelity and allows experiments with larger photon numbers. The team credited the higher efficiencies to the new light source and interferometer design.

The result has prompted discussion about cryptographic risks from future quantum devices. Some Bitcoin developers have debated protocol updates such as BIP-360 as a possible protective measure. An earlier event in which IBM hardware was used to recover a 15-bit ECC key drew analysis from Jonas Schnelli, a former Bitcoin Core maintainer, who characterized that demonstration as comparable to brute-force approaches and wrote that it did not show a new quantum advantage over classical methods.

The research team described the experiment as a step toward larger photonic systems. Researchers and technology communities will continue to monitor progress and assess implications for computing tasks and security as hardware advances.