New system checks accuracy of quantum chips: Page 3 of 3

January 15, 2020 //By
quantum chips
An international team of researchers from MIT, Google, and elsewhere have designed a system that can verify when quantum chips have accurately performed complex computations that classical computers can’t.

In experiments, the team successfully ran a popular computational task used to demonstrate quantum advantage, called “boson sampling,” which is usually performed on photonic chips. In this exercise, phase shifters and other optical components will manipulate and convert a set of input photons into a different quantum superposition of output photons. Ultimately, the task is to calculate the probability that a certain input state will match a certain output state. That will essentially be a sample from some probability distribution. But it’s nearly impossible for classical computers to compute those samples, due to the unpredictable behavior of photons. It’s been theorized that NISQ chips can compute them fairly quickly. Until now, however, there’s been no way to verify that quickly and easily, because of the complexity involved with the NISQ operations and the task itself.

“The very same properties which give these chips quantum computational power makes them nearly impossible to verify,” Carolan observes.

In experiments, the researchers were able to “unsample” two photons that had run through the boson sampling problem on their custom NISQ chip, in a fraction of time it would take traditional verification approaches.
While the method was designed for quantum verification purposes, it could also help capture useful physical properties of photon-emitting materials.


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