Applied Mathematics and Computing Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
J Chem Theory Comput. 2023 Jun 13;19(11):3313-3323. doi: 10.1021/acs.jctc.3c00150. Epub 2023 May 25.
We present a method to compute the many-body real-time Green's function using an adaptive variational quantum dynamics simulation approach. The real-time Green's function involves the time evolution of a quantum state with one additional electron with respect to the ground state wave function that is first expressed as a linear-linear combination of state vectors. The real-time evolution and the Green's function are obtained by combining the dynamics of the individual state vectors in a linear combination. The use of the adaptive protocol enables us to generate compact ansatzes on-the-fly while running the simulation. In order to improve the convergence of spectral features, Padé approximants are applied to obtain the Fourier transform of the Green's function. We demonstrate the evaluation of the Green's function on an IBM Q quantum computer. As a part of our error mitigation strategy, we develop a resolution-enhancing method that we successfully apply on the noisy data from the real-quantum hardware.
我们提出了一种使用自适应变分量子动力学模拟方法来计算多体实时格林函数的方法。实时格林函数涉及到相对于基态波函数的额外一个电子的量子态的时间演化，该波函数首先被表示为态矢量的线性-线性组合。实时演化和格林函数是通过在线性组合中组合各个态矢量的动力学来获得的。自适应协议的使用使得我们能够在运行模拟时即时生成紧凑的假设。为了提高谱特征的收敛性，应用 Padé 逼近来获得格林函数的傅里叶变换。我们在 IBM Q 量子计算机上演示了格林函数的评估。作为我们的错误缓解策略的一部分，我们开发了一种分辨率增强方法，并成功地应用于来自真实量子硬件的噪声数据。
