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arXiv 1902.00409quant-ph
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求解连续问题的量子近似优化算法

A Quantum Approximate Optimization Algorithm for continuous problems

Guillaume Verdon, Juan Miguel Arrazola, Kamil Brádler, Nathan Killoran

摘要:

提出了一种求解连续优化问题的量子近似优化算法(QAOA)。该算法是基于量子系统的动力学运动的能量潜力编码的目标函数。通过在有限的时间步近似动力学,该算法可以表示为两个非对易哈密顿算子下的交替演化。我们表明,该算法的每一步更新的波函数在其局部梯度的方向,与一个额外的动量相关的位移。对于在许多点上叠加的初始状态,该方法因此可以被解释为梯度下降的相干版本,即,“梯度下降叠加。这种方法可以用于约束和无约束优化。在计算复杂性方面,我们展示了该算法的变体如何恢复连续变量Grover搜索,以及单次迭代如何复制连续变量瞬时量子多项式电路。我们还讨论了该算法如何适用于解决离散优化问题。最后,我们通过数值模拟优化Styblinski-Tang函数来测试该算法。

英文摘要:

We introduce a quantum approximate optimization algorithm (QAOA) for continuous optimization. The algorithm is based on the dynamics of a quantum system moving in an energy potential which encodes the objective function. By approximating the dynamics at finite time steps, the algorithm can be expressed as alternating evolution under two non-commuting Hamiltonians. We show that each step of the algorithm updates the wavefunction in the direction of its local gradient, with an additional momentum-dependent displacement. For initial states in a superposition over many points, this method can therefore be interpreted as a coherent version of gradient descent, i.e., 'gradient descent in superposition.' This approach can be used for both constrained and unconstrained optimization. In terms of computational complexity, we show how variants of the algorithm can recover continuous-variable Grover search, and how a single iteration can replicate continuous-variable instantaneous quantum polynomial circuits. We also discuss how the algorithm can be adapted to solve discrete optimization problems. Finally, we test the algorithm through numerical simulation in optimizing the Styblinski-Tang function.

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