The Four Interactions

Haifeng Du

The magnetic properties of Ising model with four-spin interaction on the honeycomb lattice are studied using the Monte Carlo (MC) method. We consider both pair interaction and four-spin interaction of the system. Magnetic properties of the system with different four-spin interaction such as magnetization,internal energy,specific heat,susceptibility and critical temperature are obtained. The results show that the four-spin interaction influences the magnetic properties of system dramatically, however the influence is basically quantitative. The simulation result by MC method makes a big modification to that of EFT.

Yohei Kawakami, Tomohiro Yamaji, Aiko Yamaguchi +9 more

We theoretically present new unit circuits of Kerr parametric oscillators (KPOs) with four-body interactions, which enable the scalable embedding of all-to-all connected logical Ising spins using the Lechner-Hauke-Zoller (LHZ) scheme. These unit circuits enable four-body interactions using linear couplers, making the circuit fabrication and characterization much simpler than those of conventional unit circuits with nonlinear couplers. Numerical calculations indicate that the magnitudes of the coupling constants can be comparable to those in conventional circuits. On the basis of this theory, we designed a four-KPO circuit and experimentally confirmed the four-body correlation by measuring the pump-phase dependence of the parity of the four-KPO states. We show that the choice of the pump frequencies are important not only to enable the four-body interaction, but to cancel the effects of other unwanted interactions. Using the circuit, we demonstrated the quantum annealing based on the LHZ scheme, where the strength of the interaction between the logical Ising spins is mapped to the local field and controlled by a coherent drive applied to each KPO.

Lucas Platter

We discuss the application of an effective theory with contact interactions to the non-relativistic four-body system with short-range interactions. We have computed the binding energies of the 4He tetramer and the alpha-particle. A well-known linear correlation between three- and four-body binding energies can be understood as a result of the absence of a four-body force at leading order within this framework. Further, we give results for the binding energies of the four-boson system in two spatial dimensions.

Giampaolo Co’