Liang Jin-Min, Lv Qiao-Qiao, Wang Zhi-Xi, Fei Shao-Ming
School of Mathematical Sciences, Capital Normal University, Beijing 100048, China.
iScience. 2023 Mar 3;26(4):106306. doi: 10.1016/j.isci.2023.106306. eCollection 2023 Apr 21.
Universal quantum algorithms (UQA) implemented on fault-tolerant quantum computers are expected to achieve an exponential speedup over classical counterparts. However, the deep quantum circuits make the UQA implausible in the current era. With only the noisy intermediate-scale quantum (NISQ) devices in hand, we introduce the quantum-assisted quantum algorithm, which reduces the circuit depth of UQA via NISQ technology. Based on this framework, we present two quantum-assisted quantum algorithms for simulating open quantum systems, which utilize two parameterized quantum circuits to achieve a short-time evolution. We propose a variational quantum state preparation method, as a subroutine to prepare the ancillary state, for loading a classical vector into a quantum state with a shallow quantum circuit and logarithmic number of qubits. We demonstrate numerically our approaches for a two-level system with an amplitude damping channel and an open version of the dissipative transverse field Ising model on two sites.
在容错量子计算机上实现的通用量子算法（UQA）有望比传统算法实现指数级加速。然而，深度量子电路使得UQA在当前时代难以实现。鉴于目前只有噪声中等规模量子（NISQ）设备，我们引入了量子辅助量子算法，该算法通过NISQ技术降低了UQA的电路深度。基于此框架，我们提出了两种用于模拟开放量子系统的量子辅助量子算法，它们利用两个参数化量子电路来实现短时间演化。我们提出了一种变分量子态制备方法，作为制备辅助态的子程序，用于通过浅量子电路和对数数量的量子比特将经典向量加载到量子态中。我们通过数值方法展示了针对具有振幅阻尼通道的两能级系统以及两格点上耗散横场伊辛模型的开放版本的方法。
