The quantum instruction set (QIS) is defined as the quantum gates that are physically realizable by controlling the qubits in quantum hardware. Compiling quantum circuits into the product of the gates in a properly defined QIS is a fundamental step in quantum computing. We here propose the quantum variational instruction set (QuVIS) formed by flexibly designed multi-qubit gates for higher speed and accuracy of quantum computing. The controlling of qubits for realizing the gates in a QuVIS is variationally achieved using the fine-grained time optimization algorithm. Significant reductions in both the error accumulation and time cost are demonstrated in realizing the swaps of multiple qubits and quantum Fourier transformations, compared with the compiling by a standard QIS such as the quantum microinstruction set (QuMIS, formed by several one- and two-qubit gates including one-qubit rotations and controlled-NOT gates). With the same requirement on quantum hardware, the time cost for QuVIS is reduced to less than one half of that for QuMIS. Simultaneously, the error is suppressed algebraically as the depth of the compiled circuit is reduced. As a general compiling approach with high flexibility and efficiency, QuVIS can be defined for different quantum circuits and be adapted to the quantum hardware with different interactions.

翻译：量子指令集（QIS）定义为通过控制量子硬件中的量子比特而物理可实现的量子门集合。将量子电路编译为恰当定义QIS中门运算的乘积，是量子计算的基础步骤。本文提出由灵活设计的多量子比特门构成的量子变分指令集（QuVIS），以实现更高速度与精度的量子计算。通过细粒度时间优化算法，变分地完成对实现QuVIS中门所需量子比特的控制。与采用标准QIS（如量子微指令集QuMIS，由若干单比特和双比特门组成，包括单比特旋转门和受控非门）的编译相比，在实现多量子比特交换与量子傅里叶变换时，QuVIS显著降低了误差累积与时间开销。在量子硬件要求相同的情况下，QuVIS的时间开销降至QuMIS的一半以下，同时由于编译电路深度降低，误差得到代数级抑制。作为一种具备高灵活性与高效率的通用编译方法，QuVIS可针对不同量子电路定义，并适配具有不同相互作用的量子硬件。