TY - JOUR

T1 - Enhancing quantum annealing performance by a degenerate two-level system

AU - Watabe, Shohei

AU - Seki, Yuya

AU - Kawabata, Shiro

N1 - Funding Information:
We thank R. van Bijnen, W. Lechner, Y. Matsuzaki, T. Ishikawa, T. Yamamoto, and T. Nikuni for fruitful discussions and comments. Two of the authors (S.W. and S.K.) were supported by Nanotech CUPAL, Japan Science and Technology Agency (JST). Y.S. and S.K. were supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan.
Publisher Copyright:
© 2020, The Author(s).

PY - 2020/12/1

Y1 - 2020/12/1

N2 - Quantum annealing is an innovative idea and method for avoiding the increase of the calculation cost of the combinatorial optimization problem. Since the combinatorial optimization problems are ubiquitous, quantum annealing machine with high efficiency and scalability will give an immeasurable impact on many fields. However, the conventional quantum annealing machine may not have a high success probability for finding the solution because the energy gap closes exponentially as a function of the system size. To propose an idea for finding high success probability is one of the most important issues. Here we show that a degenerate two-level system provides the higher success probability than the conventional spin-1/2 model in a weak longitudinal magnetic field region. The physics behind this is that the quantum annealing in this model can be reduced into that in the spin-1/2 model, where the effective longitudinal magnetic field may open the energy gap, which suppresses the Landau–Zener tunneling providing leakage of the ground state. We also present the success probability of the Λ-type system, which may show the higher success probability than the conventional spin-1/2 model.

AB - Quantum annealing is an innovative idea and method for avoiding the increase of the calculation cost of the combinatorial optimization problem. Since the combinatorial optimization problems are ubiquitous, quantum annealing machine with high efficiency and scalability will give an immeasurable impact on many fields. However, the conventional quantum annealing machine may not have a high success probability for finding the solution because the energy gap closes exponentially as a function of the system size. To propose an idea for finding high success probability is one of the most important issues. Here we show that a degenerate two-level system provides the higher success probability than the conventional spin-1/2 model in a weak longitudinal magnetic field region. The physics behind this is that the quantum annealing in this model can be reduced into that in the spin-1/2 model, where the effective longitudinal magnetic field may open the energy gap, which suppresses the Landau–Zener tunneling providing leakage of the ground state. We also present the success probability of the Λ-type system, which may show the higher success probability than the conventional spin-1/2 model.

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U2 - 10.1038/s41598-019-56758-4

DO - 10.1038/s41598-019-56758-4

M3 - Article

C2 - 31924805

AN - SCOPUS:85077709933

VL - 10

JO - Scientific Reports

JF - Scientific Reports

SN - 2045-2322

IS - 1

M1 - 146

ER -