论文标题
Bloch矢量扩增的非线性和非CP门
Nonlinear and non-CP gates for Bloch vector amplification
论文作者
论文摘要
任何状态r =（x，y，z）的任何状态，以保利为基础编写并以纯状态r =（0,0,1）初始化，可以通过组成三个量子操作来制备：两个统一的旋转门以达到bloch sphere上的纯状态，然后用去极化门降低一个纯净的状态。在这里，我们根据增加或放大| r |在Bloch球中心的初始初始化的Qubits的互补状态预先准备协议，r = 0。达到所需的值，然后旋转。 Bloch矢量扩增可能会或可能不会增加量子能量，但必然会增加纯度并降低熵。通过将通道的固定点远离r = 0，可以通过线性马尔可夫CPTP通道来实现扩增，但随着固定点的接近，结果栅极遭受临界速度的损失。在这里，我们考虑了基于线性和非线性马尔可夫PTP通道的替代设计，这些设计相对于线性CPTP通道提供了优势，即bloch矢量放大而无需减速。这些操作模拟了量子的热力学箭头的逆转，并将提供非CP动力学的惊人实验演示。
Any state r = (x,y,z) of a qubit, written in the Pauli basis and initialized in the pure state r = (0,0,1), can be prepared by composing three quantum operations: two unitary rotation gates to reach a pure state on the Bloch sphere, followed by a depolarization gate to decrease |r|. Here we discuss the complementary state-preparation protocol for qubits initialized at the center of the Bloch ball, r=0, based on increasing or amplifying |r| to its desired value, then rotating. Bloch vector amplification may or may not increase qubit energy, but it necessarily increases purity and decreases entropy. Amplification can be achieved with a linear Markovian CPTP channel by placing the channel's fixed point away from r=0, making it nonunital, but the resulting gate suffers from a critical slowing down as that fixed point is approached. Here we consider alternative designs based on linear and nonlinear Markovian PTP channels, which offer benefits relative to linear CPTP channels, namely fast Bloch vector amplification without deceleration. These operations simulate a reversal of the thermodynamic arrow of time for the qubit and would provide striking experimental demonstrations of non-CP dynamics.
