A frequently encountered source of systematic error in quantum computations is imperfections in the control pulses which are the classical fields that control qubit gate operations. From an analysis of the quantum-mechanical time-evolution operator of the spin wavefunction, it has been demonstrated that composite pulses can mitigate certain systematic errors and an appealing geometric interpretation was developed for the design of error-suppressing composite pulses. Here we show that these same pulse sequences can be obtained within a quasi-classical framework. This raises the question of whether error-correction procedures exist that exploit entanglement in a manner that can not be reproduced in the quasi-classical formulation.

量子计算中经常遇到的系统误差源是控制脉冲的缺陷，而控制脉冲是控制量子位门控操作的经典领域。通过对自旋波函数的量子力学时间演化算符进行分析，已证明复合脉冲可以减轻某些系统误差，并且为抑制误差的复合脉冲的设计开发了一种引人入胜的几何解释。在这里，我们表明可以在准经典框架内获得这些相同的脉冲序列。这就提出了一个问题，即是否存在纠错程序，这种纠错程序无法以准经典公式中的再现方式进行纠缠。