[3H01-04] Young Researcher's Session

10:15 AM - 10:30 AM JST(1:15 AM - 1:30 AM UTC)

[3H02] Implementation of Complex Unitary Coupled-Cluster Wavefunctions

*Hiromichi Hayashi¹, Moeko Harada¹, Takeshi Sato¹, Kenichi L Ishikawa¹ (1. UTokyo)

Keywords:

ab-initio calculation,quantum computing,unitary coupled-cluster method

Implementing quantum circuits with shallow depths is crucial for performing high-precision quantum chemistry calculations. The quantum circuit for the UCC (Unitary Coupled-Cluster) method, a representative molecular orbital method for obtaining the wave function of a multi-electron system, becomes extremely long when implemented naively. Therefore, an implementation using a multi-control Ry gate has been proposed to reduce the circuit depth. However, this implementation is based on real wave functions and cannot be used directly in a wide range of applications. Previous studies have extended this implementation to complex wave functions, but they require twice the depth of the real wave function circuit. Therefore, in this study, we show that complex wave functions can be expressed with almost no change in circuit depth by representing UCC method complex parameters in polar form. Furthermore, we experimentally demonstrate that the implementation of this shallow single-electron excitation circuit can clearly reduce errors compared to conventional methods.