Saida Daisuke, Hidaka Mutsuo, Miyake Kouhei, Imafuku Kentaro, Yamanashi Yuki
Device Technology Research Institute, National Institute of Advanced Industrial Science and Technology, Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, Japan.
Quantum laboratory, Fujitsu research, 1-1 Kamikodanaka, 4-chome, Nakahara-ku, Kawasaki, Kanagawa, 211-8588, Japan.
Sci Rep. 2022 Sep 23;12(1):15894. doi: 10.1038/s41598-022-20172-0.
The applicability of quantum annealing to various problems can be improved by expressing the Hamiltonian using a circuit satisfiability problem. We investigate the detailed characteristics of the NOR/NAND functions of a superconducting quantum circuit, which are the basic building blocks to implementing various types of problem Hamiltonians. The circuit is composed of superconducting flux qubits with all-to-all connectivity, where direct magnetic couplers are utilized instead of the variable couplers in the conventional superconducting quantum circuit. This configuration provides efficient scalability because the problem Hamiltonian is implemented using fewer qubits. We present an experiment with a complete logic operation of NOR/NAND, in which the circuit produces results with a high probability of success for arbitrary combinations of inputs. The features of the quantum circuit agree qualitatively with the theory, especially the mechanism for an operation under external flux modulation. Moreover, by calibrating the bias conditions to compensate for the offset flux from the surrounding circuit, the quantum circuit quantitatively agrees with the theory. To achieve true quantum annealing, we discuss the effects of the reduction in electric noise in quantum annealing.
通过使用电路可满足性问题来表达哈密顿量，可以提高量子退火对各种问题的适用性。我们研究了超导量子电路的或非/与非门功能的详细特性，这些功能是实现各种类型问题哈密顿量的基本构建块。该电路由具有全对全连接性的超导通量量子比特组成，其中使用直接磁耦合器代替传统超导量子电路中的可变耦合器。这种配置提供了高效的可扩展性，因为问题哈密顿量是用更少的量子比特实现的。我们展示了一个或非/与非门完整逻辑操作的实验，其中该电路对于任意输入组合都能以高成功率产生结果。量子电路的特性在定性上与理论相符，特别是在外部磁通调制下的操作机制。此外，通过校准偏置条件以补偿来自周围电路的偏移磁通，量子电路在定量上与理论相符。为了实现真正的量子退火，我们讨论了量子退火中电噪声降低的影响。
