论文标题
超高效率复合旋转量子门
Ultrahigh-fidelity composite rotational quantum gates
论文作者
论文摘要
提出了在Bloch球上产生任意预定量旋转的复合脉冲序列。复合序列最多包含17个脉冲，并且可以在脉冲振幅和脉冲持续时间中补偿多达8个实验误差。得出了三个基本量子门的复合序列 - x（非），哈玛德和任意旋转。提出了三类复合序列 - 一个对称和两个不对称。它们作为最低成员的两个众所周知的复合序列 - 三脉冲对称的s骨脉冲和四脉冲不对称的BB1脉冲，分别补偿了一阶和二阶错误。较短的序列是通过分析得出的，而较长的序列是数值的（而不是通过嵌套和串联，就像迄今为止完成的一样）。因此，此处得出的复合序列以速度或准确性或两者兼而有之匹配现有的序列。例如，我们得出了一个二阶复合序列，该序列比著名的BB1序列快（约13 \％）。对于高阶序列，加速变得更加明显。这对于量子信息处理很重要，因为此处得出的序列为查找超高忠诚度和高速速度之间的最佳位置提供了更多选择。
Composite pulse sequences, which produce arbitrary pre-defined rotations of a qubit on the Bloch sphere, are presented. The composite sequences contain up to 17 pulses and can compensate up to eight orders of experimental errors in the pulse amplitude and the pulse duration. Composite sequences for three basic quantum gates -- X (NOT), Hadamard and arbitrary rotation -- are derived. Three classes of composite sequences are presented -- one symmetric and two asymmetric. They contain as their lowest members two well-known composite sequences -- the three-pulse symmetric SCROFULOUS pulse and the four-pulse asymmetric BB1 pulse, which compensate first and second-order errors, respectively. The shorter sequences are derived analytically, and the longer ones numerically (instead by nesting and concatenation, as mostly done hitherto). Consequently, the composite sequences derived here match or outperform the existing ones in terms of either speed or accuracy, or both. For example, we derive a second-order composite sequence, which is faster (by about 13\%) than the famous BB1 sequence. For higher-order sequences the speed-up becomes much more pronounced. This is important for quantum information processing as the sequences derived here provide more options for finding the sweet spot between ultrahigh fidelity and high speed.
