As a milestone for general-purpose computing machines, we demonstrate that quantum processors can be programed to efficiently simulate dynamics that are not native to the hardware. Moreover, on noisy devices without error correction, we show that simulation results are significantly improved when the quantum program is compiled using modular gates instead of a restricted set of standard gates. We demonstrate the general methodology by solving a cubic interaction problem, which appears in nonlinear optics, gauge theories, as well as plasma and fluid dynamics. To encode the non-native Hamiltonian evolution, we decompose the Hilbert space into a direct sum of invariant subspaces in which the nonlinear problem is mapped to a finite-dimensional Hamiltonian simulation problem. In a three-states example, the resultant unitary evolution is realized by a product of approximately 20 standard gates, using which approximately ten simulation steps can be carried out on state-of-the-art quantum hardware before results are corrupted by decoherence. In comparison, the simulation depth is improved by more than an order of magnitude when the unitary evolution is realized as a single cubic gate, which is compiled directly using optimal control. Alternatively, parametric gates may also be compiled by interpolating control pulses. Modular gates thus obtained provide high-fidelity building blocks for quantum Hamiltonian simulations.

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在嘈杂的量子机器上模拟非本机三次相互作用

作为通用计算机的一个里程碑，我们证明了量子处理器可以通过编程来有效地模拟非硬件固有的动力学。此外，在没有纠错的嘈杂设备上，我们表明当使用模块化门而不是一组受限制的标准门编译量子程序时，模拟结果得到显着改善。我们通过解决非线性光学、规范理论以及等离子体和流体动力学中出现的三次相互作用问题来演示一般方法。为了编码非本地哈密顿演化，我们将希尔伯特空间分解为不变子空间的直接和，其中非线性问题被映射到有限维哈密顿模拟问题。在三态的例子中，由此产生的幺正演化是通过大约 20 个标准门的乘积实现的，在结果被退相干破坏之前，可以在最先进的量子硬件上执行大约十个模拟步骤。相比之下，当幺正演化作为单个立方门实现时，模拟深度提高了一个数量级以上，这是直接使用优化控制编译的。或者，也可以通过内插控制脉冲来编译参数门。由此获得的模块化门为量子哈密顿模拟提供了高保真构建块。当幺正演化实现为单个立方门时，模拟深度提高了一个数量级以上，这是使用优化控制直接编译的。或者，也可以通过内插控制脉冲来编译参数门。由此获得的模块化门为量子哈密顿模拟提供了高保真构建块。当幺正演化实现为单个立方门时，模拟深度提高了一个数量级以上，这是使用优化控制直接编译的。或者，也可以通过内插控制脉冲来编译参数门。由此获得的模块化门为量子哈密顿模拟提供了高保真构建块。