论文标题
详尽的搜索使用量子计算机上的假想时间演变来搜索最佳分子几何形状
Exhaustive search for optimal molecular geometries using imaginary-time evolution on a quantum computer
论文作者
论文摘要
我们提出了一种非不同的方案，用于针对初量化的Eigensolver进行分子的几何优化，这是一种使用量子计算机上的概率假想时间演化（PITE）的量子化学框架。虽然分子中的电子被视为量子机械颗粒，但核被视为经典点电荷。我们将电子状态和候选分子几何形状编码为多数状态的叠加，从而带来量子优势。由重复测量结果形成的直方图给出了能量表面的全局最小值。我们证明了电路深度尺度为电子编号n_e的o（n_e^2 poly（log n_e）），如果可以使用额外的o（n_e log n_e）Qubits，则可以将其减少为O（n_e poly（log n_e））。我们通过数值模拟证实了该方案。新的有效方案将有助于在量子计算机上实现实用量子化学的可扩展性。作为该方案的一种特殊情况，仅接受由带电粒子组成的经典系统。我们还研究了适合各种计算的方案，该方案优先考虑噪音中间尺度量子（NISQ）设备的节省电路深度。
We propose a nonvariational scheme for geometry optimization of molecules for the first-quantized eigensolver, a recently proposed framework for quantum chemistry using the probabilistic imaginary-time evolution (PITE) on a quantum computer. While the electrons in a molecule are treated in the scheme as quantum mechanical particles, the nuclei are treated as classical point charges. We encode both electronic states and candidate molecular geometries as a superposition of many-qubit states, leading to quantum advantage. The histogram formed by outcomes of repeated measurements gives the global minimum of the energy surface. We demonstrate that the circuit depth scales as O (n_e^2 poly(log n_e)) for the electron number n_e, which can be reduced to O (n_e poly(log n_e)) if extra O (n_e log n_e) qubits are available. We corroborate the scheme via numerical simulations. The new efficient scheme will be helpful for achieving scalability of practical quantum chemistry on quantum computers. As a special case of the scheme, a classical system composed only of charged particles is admitted. We also examine the scheme adapted to variational calculations that prioritize saving circuit depths for noisy intermediate-scale quantum (NISQ) devices.
