Experimental Quantum Computing to Solve Systems of Linear Equations
Xiang Cai, Christian Weedbrook, Zu-En Su, Minjia Chen, Mile Gu, Mingzheng Zhu, Li Li, Nai-Le Liu, Chao‐Yang Lu, Jian-Wei Pan · Physical Review Letters · 2013
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.