Experimental Quantum Computing to Solve Systems of Linear Equations

X. -D. Cai, Christian Weedbrook, Z. -E. Su, M. -C. Chen, Mile Gu, M. -J. Zhu, L. Li, N. -L. Liu, Chao-Yang Lu, Jian-Wei Pan

Published 2013-02-18, updated 2013-06-03Version 2

Solving linear systems of equations is ubiquitous in all areas of science and engineering. With rapidly growing data sets, such a task can be intractable for classical computers, as the best known classical algorithms require a time proportional to the number of variables N. A recently proposed quantum algorithm shows that quantum computers could solve linear systems in a time scale of order log(N), giving an exponential speedup over classical computers. Here we realize the simplest instance of this algorithm, solving 2*2 linear equations for various input vectors on a quantum computer. We use four quantum bits and four controlled logic gates to implement every subroutine required, demonstrating the working principle of this algorithm.