A quantum computer solves a 9,000-year-old problem in 36 microseconds

Quantum computers, still in experimentation, are based on quantum bits, but can also use photons, the smallest particle of light energy. Now scientists have made progress in completing a task in just 36 microseconds the classics would take almost 9,000 years.

The description of this quantum photonic processor, called Borealis, is published in the journal Nature and its managers assure that it is the greatest quantum advantage photonic experiment.

“On average, the best current algorithms and supercomputers would take more than 9,000 years” to do the job, researchers from Xanadu, a Canadian quantum technology company, and the US National Institute of Standards and Technology stress in their paper.

This system presents improvements over previously demonstrated photonic devices and may represent an important step towards the creation of quantum machines, summarizes Jonathan Lavoie’s scientific team.

To date, only a small number of experiments have reported this achievement, mostly in those models based on quantum bits. In 2019 Google claimed to have achieved quantum supremacy, which was questioned by IBM.

The demonstration of this advantage is now published in a photon processor and an approach to demonstrate so-called boson sampling: the photon is an example of a boson, an elementary particle.

This sampling is a calculation that is carried out in a circuit through which the photons travel, with a series of inputs and outputs and a network of mirrors and fixed lenses, among other quantum optical instruments.

In reality, the calculation consists of establishing, based on some parameters, how many photons end up, due to the changes that occur inside the circuit, in a given output lane and not in another.

These transformations can be caused, for example, by the beam splitters that cause there to be a certain probability that the photons change lanes in the circuit, achieving their redistribution at the output.

High complexity calculations


Xanadu researchers putting the finishing touches on their system.

And although it seems simple, years ago it was shown that doing this calculation –find out how many photons are in a given lane output – quickly on conventional machines is not possible.

And it is that there is a threshold of photons above which classical computers are not able to perform the calculation in a reasonable time.

In the Nature study, the team achieved the largest boson sampling to date, with 216 lanes (125 photons on average) and a calculation in record time: 0.000036 seconds.

“The results have to be framed in the race to demonstrate quantum supremacy,” summarizes the physicist, who highlights that the system could be easily programmed to generate certain states “with which it is known that universal quantum computing can be carried out,” commented one of participants.

This -he adds- would answer the most common criticism of boson sampling: its practical uselessness beyond the demonstration of quantum supremacy.

With information from agencies.

By Editor

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