Computational multiqubit tunnelling in programmable quantum annealers
Venue
Nature Communications, vol. 7 (2016)
Publication Year
2016
Authors
Sergio Boixo, Vadim N Smelyanskiy, Alireza Shabani, Sergei V Isakov, Mark Dykman, Vasil S Denchev, Mohammad H Amin, Anatoly Yu Smirnov, Masoud Mohseni, Hartmut Neven
BibTeX
Abstract
Quantum tunnelling is a phenomenon in which a quantum state traverses energy
barriers higher than the energy of the state itself. Quantum tunnelling has been
hypothesized as an advantageous physical resource for optimization in quantum
annealing. However, computational multiqubit tunnelling has not yet been observed,
and a theory of co-tunnelling under high- and low-frequency noises is lacking. Here
we show that 8-qubit tunnelling plays a computational role in a currently available
programmable quantum annealer. We devise a probe for tunnelling, a computational
primitive where classical paths are trapped in a false minimum. In support of the
design of quantum annealers we develop a nonperturbative theory of open quantum
dynamics under realistic noise characteristics. This theory accurately predicts the
rate of many-body dissipative quantum tunnelling subject to the polaron effect.
Furthermore, we experimentally demonstrate that quantum tunnelling outperforms
thermal hopping along classical paths for problems with up to 200 qubits containing
the computational primitive.
