Chinese photonic quantum computer demonstrates quantum supremacy
— Read on phys.org/news/2020-12-chinese-photonic-quantum-supremacy.html

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Boson sampling is a means for calculating the output of a straight-line optical circuit that has multiple inputs and outputs. It is carried out by constructing a machine in which photons are sent into a circuit in parallel, and once inside, are split by beam splitters. The split photons continue through the circuit, encountering mirrors and other beam splitters. Notably, if two photons happen to encounter the same splitter simultaneously, both unsplit photons will follow one of the paths away from the splitter. The process is repeated, resulting in a distribution of numbers that represent the network output. Conventional computers become bogged down very quickly when trying to calculate distributions of such a system. Jiuzhang was built to handle 100 inputs and 100 outputs using 300 beam splitters and 75 mirrors.

The researchers found that it took Jiuzhang approximately 200 seconds to provide an answer. They noted that it would have taken the world’s fastest supercomputer approximately 2.5 billion years to carry out the same calculations—a clear example of quantum supremacy.