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First-quantized eigensolver for ground and excited states of electrons under a magnetic field

Taichi Kosugi, Hirofumi Nishi, and Yu-ichiro Matsushita published the paper on Japanese Journal of Applied Physics 62, 062004 (2023)

Fig.1   Fig.2

The study of the effects of external magnetic fields on materials or molecules has become essential for the development and refinement of advanced techniques such as NMR. However, calculations incorporating many-electron effects are limited to small-scale calculations on classical computers. We have already proposed a method to perform quantum chemical calculations in the first-quantized form based on

probabilistic imaginary- time evolution (PITE) on a quantum computer without such limitations.

In this study, we extend the framework and develop a method to obtain the ground state of molecular systems in the presence of a uniform external magnetic field. Through estimation of the required computational resources, we found that the effect of the magnetic field can be efficiently introduced by an additional circuit in Fig. 1 with a depth linear with the number of qubits assigned to each electron.

Fig. 2 shows the simulation results of the present method applied to a single electron in a confinement potential, and shows that the current density can be obtained from measurements on qubits.



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