A Chinese quantum computer prototype has accomplished in three minutes a task which would have taken the next most advanced supercomputer billions of years.
If the claim holds up, the quantum computer known as Jiuzhang will be the second computer to reach quantum supremacy, achieved when a quantum computer performs a task impossible for both conventional computers, as well as the fastest existing quantum computer.
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Quantum computers use quantum bits or qubits, which can exist in multiple states simultaneously. The theoretical advantage is huge, but actually building a quantum computer is an enormous undertaking of physics and engineering. Jiuzhang uses optical circuits and is limited to computations around light particle behavior. Google’s Sycamore, the first quantum computer to achieve quantum supremacy, is chip-based and closer to the build of a conventional computer.
To prove quantum supremacy, the lab assigned Jiuzhang a “Gaussian Boson Sampling” (GBS) task. That is, Jiuzhang was required to compute possibilities when multiple photons arrived at certain circuit components at the same time — something conventional computers cannot do. Jiuzhang successfully detected 76 photons in its best test, averaging 43 photons across all.
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It took 200 seconds to do this, whereas the task could have taken China’s Taihe supercomputer between 2 and 3 billion years. Although Jiuzhang is specialized for GBS and its ability range is limited, this is still a momentous achievement, as the field of quantum physics is driven largely by studies on photon behavior.
China’s success in quantum computing is no accident. The state is building a $10 billion USD National Laboratory for Quantum Information Sciences, and in his paper’s introductory statement, Jiuzhang team leader Pan Jian Wei acknowledged that his lab’s breakthrough placed China at the forefront of quantum computing research, performing calculations 10 billion times faster than Sycamore.
