Physical Society Colloquium

A classical adversarial view on (photonic) quantum computational advantage

Nicolas Quesada

Département de génie physique
Polytechnique Montréal

Recently, experiments by groups at the University of Science and Technology of China and Xanadu (a quantum computing startup in Toronto) have claimed to demonstrate quantum computational advantage. Both groups built photonic processors, so-called Gaussian Boson Samplers, that demonstrate the ability of current quantum devices to significantly outperform classical computers at the task of generating random numbers from a very special type of probability distribution.

We will start by going over crucial assumptions in the mathematical arguments presented to claim that the tasks performed by these machines cannot be performed efficiently on a classical computer, no matter what type of clever algorithm you use or could come up with. Secondly, we will ask how fast an adversary with access only to classical computational resources could simulate the calculations these machines perform. Finally, we will share some recent progress on the question of how quantum sampling machines can be certified: how one can use the output of a Gaussian Boson Sampler, namely collections of random numbers, to argue that the machine functioned correctly.