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arXiv quant-ph/0203066quant-ph
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时间干涉术：一种在扭曲快速通过过程中控制量子比特跃迁的机制及其在量子计算中的应用

Temporal Interferometry: A Mechanism for Controlling Qubit Transitions During Twisted Rapid Passage with Possible Application to Quantum Computing

Frank Gaitan

备注：
29 pages, 16 figures, submitted to Phys. Rev. A
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摘要：

在绝热快速通过实验中，二能级系统（量子比特）的布洛赫矢量通过缓慢反转它所耦合的外部场来反转，并且它最初沿着它对齐。在扭转快速通过中，外场被允许围绕其初始方向以方位角$ϕ(t)$扭转，同时它被反转。对于多项式扭曲：$ϕ(t) \sim Bt^{n}$。我们表明，对于$n \geq 3$，多个避免交叉可以发生在外部场的反转，这些交叉引起强干扰的量子比特跃迁概率的影响。转移概率被发现是一个函数的扭曲强度$B$，它可以用来控制避免交叉的时间间隔，因此的字符的干扰。相长干涉和相消干涉都是可能的。干涉效应是波函数的时间相位相干性的结果。通过改变所避免的交叉的时间间隔来改变这种相干性的能力使得具有可调节的扭曲强度的扭曲快速通过到时间干涉仪中，通过该时间干涉仪可以极大地增强或抑制量子比特跃迁。讨论了这种干涉机制在构造快速容错量子CNOT和NOT门中的可能应用。

英文摘要：

In an adiabatic rapid passage experiment, the Bloch vector of a two-level system (qubit) is inverted by slowly inverting an external field to which it is coupled, and along which it is initially aligned. In twisted rapid passage, the external field is allowed to twist around its initial direction with azimuthal angle $ϕ(t)$ at the same time that it is inverted. For polynomial twist: $ϕ(t) \sim Bt^{n}$. We show that for $n \geq 3$, multiple avoided crossings can occur during the inversion of the external field, and that these crossings give rise to strong interference effects in the qubit transition probability. The transition probability is found to be a function of the twist strength $B$, which can be used to control the time-separation of the avoided crossings, and hence the character of the interference. Constructive and destructive interference are possible. The interference effects are a consequence of the temporal phase coherence of the wavefunction. The ability to vary this coherence by varying the temporal separation of the avoided crossings renders twisted rapid passage with adjustable twist strength into a temporal interferometer through which qubit transitions can be greatly enhanced or suppressed. Possible application of this interference mechanism to construction of fast fault-tolerant quantum CNOT and NOT gates is discussed.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

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