AsianScientist (Dec. 29, 2020) – By carefully mapping out beams of laser light, Chinese researchers have demonstrated quantum supremacy—a lofty goal whereby quantum computers perform computations no classical computer can. Their results were published in Science.
Classical computers—the computers we use in our everyday lives—have gone a long way in the past decades. For instance, our smartphones have a hundred thousand times more computing power than the room-sized computers first used to send astronauts to the moon.
To create even more powerful computers, scientists are increasingly harnessing quantum phenomena. In classical computers, bits of information are traditionally represented using a strict binary of 0s and 1s. Through phenomena like superposition, the quantum bits or qubits of quantum computers can correspond to both 0 and 1 at the same time.
The ability to simultaneously process multiple states of information through qubits gives quantum computers the power to greatly outperform their classical counterparts in certain tasks. Consider boson sampling, an experiment that seeks to measure the random distribution of light particles or photons as they travel through an intricate maze. Such a set-up would take China’s fastest supercomputer, the Sunway TaihuLight, two billion years to compute.
In contrast, researchers led by Professor Pan Jianwei at the University of Science and Technology China built a quantum computing system that could perform boson sampling in 200 seconds. The system, called Jiuzhang, includes a custom-design laser device that generates photons as well as hundreds of prisms and mirrors to randomize the photons’ path.
There are other approaches to building quantum computers that do not use photons. For instance, in 2019, Google claimed quantum supremacy through its 53-qubit Sycamore quantum processor. Sycamore, which was built with superconducting circuits typically kept at ultralow temperatures, took a little over three minutes to perform a calculation that would have taken a supercomputer 10,000 years.
However, given the low-temperature requirements of superconductors, Google’s Sycamore guzzles much more power compared to the photonics-based approach of China’s Jiuzhang, which operates at room temperature.
Jiuzhang’s quantum supremacy represents another feather in the cap for Pan, hailed by some as China’s Father of Quantum. In 2018, Pan led pioneering experiments with China’s first quantum satellite Micius—like an unhackable video chat between Beijing and Vienna. At 1,400 kilometers, Pan’s team also holds the world record for the longest distance of quantum teleportation when they made a particle teleport from Earth to Micius in orbit in 2017.
“We have shown that we can use photons, the fundamental unit of light, to demonstrate quantum computational power well beyond the classical counterpart,” said Pan to Nature.
The article can be found at: Zhong et al. (2020) Quantum computational advantage using photons.
Copyright: Asian Scientist Magazine; Photo: Shutterstock.
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