title: Adiabatic Quantum Search in Open Systems.
abstract: Adiabatic quantum algorithms represent a promising approach to universal quantum computation. In isolated systems, a key limitation to such algorithms is the presence of avoided level crossings, where gaps become extremely small. In open quantum systems, the fundamental robustness of adiabatic algorithms remains unresolved. Here, we study the dynamics near an avoided level crossing associated with the adiabatic quantum search algorithm, when the system is coupled to a generic environment. At zero temperature, we find that the algorithm remains scalable provided the noise spectral density of the environment decays sufficiently fast at low frequencies. By contrast, higher order scattering processes render the algorithm inefficient at any finite temperature regardless of the spectral density, implying that no quantum speedup can be achieved. Extensions and implications for other adiabatic quantum algorithms will be discussed.
authors: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors: Dominik S
authors: DS
authors: Wild
authors: Department of Physics and Walter Burke Institute, California Institute of Technology, Pasadena, California 91125, USA.|Department of Engineering Science and Physics, CUNY College of Staten Island, Staten Island, New York 10134, USA.
authors: Sarang
authors: S
authors: Gopalakrishnan
authors: Department of Physics, Walter Schottky Institute, and Institute for Advanced Study, Technical University of Munich, 85748 Garching, Germany.
authors: Michael
authors: M
authors: Knap
authors: Department of Physics, University of California, Berkeley, California 94720, USA.
authors: Norman Y
authors: NY
authors: Yao
authors: Department of Physics, Harvard University, Cambridge, Massachusetts 02138, USA.
authors: Mikhail D
authors: MD
authors: Lukin