Dmitry Petrov, CNRS researcher LPTMS
Title: Quantum annealing with more than one hundred qubits
Authors: Sergio Boixo, Troels F. Ronnow, Sergei V. Isakov, Zhihui Wang, David Wecker, Daniel A. Lidar, John M. Martinis, and Matthias Troyer
The paper is not publicly available as it is submitted to Nature, but I explained Matthias our Journal Club idea and he sent me the preprint asking to keep it for our private use. I will put the preprint on our coffee table together with the D-Wave Systems wikipedia page. Enjoy.
At a time when quantum effects start to pose limits to further miniaturisation of devices and the exponential performance increase due to Moore’s law, quantum technology is maturing to the point where quantum devices, such as quantum communication systems, quantum random number generators and quantum simulators, may be built with powers exceeding the performance of classical computers. A quantum annealer, in particular, finds solutions to hard optimisation problems by evolving a known initial configuration towards the ground state of a Hamiltonian that encodes an optimisation problem. Here, we present results from experiments on a 108 qubit D-Wave One device based on superconducting flux qubits. The correlations between the device and a simulated quantum annealer demonstrate that the device performs quantum annealing: unlike classical thermal annealing it exhibits a bimodal separation of hard and easy problems, with small-gap avoided level crossings characterizing the hard problems. To assess the computational power of the quantum annealer we compare it to optimised classical algorithms. We discuss how quantum speedup could be detected on devices scaled to a larger number of qubits where the limits of classical algorithms are reached.