Quantum computing. Defining and detecting quantum speedup.
Troels F Rønnow, Zhihui Wang, Joshua Job, Sergio Boixo, Sergei V Isakov, David Wecker, John M Martinis, Daniel A Lidar, Matthias Troyer
Author Information
Troels F Rønnow: Theoretische Physik, ETH (Eidgenössische Technische Hochschule) Zurich, 8093 Zurich, Switzerland.
Zhihui Wang: Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA. Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, CA 90089, USA.
Joshua Job: Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, CA 90089, USA. Department of Physics, University of Southern California, Los Angeles, CA 90089, USA.
Sergio Boixo: Google, 150 Main Street, Venice Beach, CA 90291, USA. Information Sciences Institute, University of Southern California, Los Angeles, CA 90089, USA.
Sergei V Isakov: Google, Brandschenkestrasse 110, 8002 Zurich, Switzerland.
David Wecker: Quantum Architectures and Computation Group, Microsoft Research, Redmond, WA 98052, USA.
John M Martinis: Department of Physics, University of California Santa Barbara, CA 93106-9530, USA.
Daniel A Lidar: Department of Chemistry, University of Southern California, Los Angeles, CA 90089, USA. Center for Quantum Information Science and Technology, University of Southern California, Los Angeles, CA 90089, USA. Department of Physics, University of Southern California, Los Angeles, CA 90089, USA. Information Sciences Institute, University of Southern California, Los Angeles, CA 90089, USA. Department of Electrical Engineering, University of Southern California, Los Angeles, CA 90089, USA.
The development of small-scale quantum devices raises the question of how to fairly assess and detect quantum speedup. Here, we show how to define and measure quantum speedup and how to avoid pitfalls that might mask or fake such a speedup. We illustrate our discussion with data from tests run on a D-Wave Two device with up to 503 qubits. By using random spin glass instances as a benchmark, we found no evidence of quantum speedup when the entire data set is considered and obtained inconclusive results when comparing subsets of instances on an instance-by-instance basis. Our results do not rule out the possibility of speedup for other classes of problems and illustrate the subtle nature of the quantum speedup question.
