arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 1611.07129quant-ph
收藏

具有含时$δ$函数势的盒中粒子

Particle in a box with a time-dependent $δ$-function potential

Seung Ki Baek, Su Do Yi, Minjae Kim

摘要:

在量子信息处理中,人们经常考虑在包含粒子的盒子中插入屏障以产生一位香农熵。我们将这个问题表示为一维薛定谔方程,其势函数为含时的$δ$函数。这是一个自然的推广粒子在一个盒子里,一个典型的例子量子力学,我们提出了这个问题的分析和数值研究。推导出一个精确的Volterra型积分方程,由一个无限总和的模式,我们表明,近似公式与最低频率的模式正确捕捉的定性行为的波函数。如果我们考虑到数百种模式,我们的数值计算表明,量子绝热定理实际上给出了一个非常好的近似,即使势垒高度在有限时间内发散,只要它足够长,比粒子的特征时间尺度。特别是,如果势垒缓慢地插入在一个不对称的位置,粒子是本地化的插入本身,根据预测的绝热定理。另一方面,当势垒被快速插入时,由于能量转移到粒子,波函数在插入之后变得粗糙。无论势垒的位置如何,快速插入都会使粒子处于非定域状态,这样我们就可以通过哪一侧的测量来获得有意义的信息。我们的数值程序提供了一种精确的方法来计算整个过程中的波函数,从中可以估计出任意插入协议的信息量。

英文摘要:

In quantum information processing, one often considers inserting a barrier into a box containing a particle to generate one bit of Shannon entropy. We formulate this problem as a one-dimensional Schrödinger equation with a time-dependent $δ$-function potential. It is a natural generalization of the particle in a box, a canonical example of quantum mechanics, and we present analytic and numerical investigations on this problem. After deriving an exact Volterra-type integral equation, composed of an infinite sum of modes, we show that approximate formulas with the lowest-frequency modes correctly capture the qualitative behavior of the wave function. If we take into account hundreds of modes, our numerical calculation shows that the quantum adiabatic theorem actually gives a very good approximation even if the barrier height diverges within finite time, as long as it is sufficiently longer than the characteristic time scale of the particle. In particular, if the barrier is slowly inserted at an asymmetric position, the particle is localized by the insertion itself, in accordance with a prediction of the adiabatic theorem. On the other hand, when the barrier is inserted quickly, the wave function becomes rugged after the insertion because of the energy transfer to the particle. Regardless of the position of the barrier, the fast insertion leaves the particle unlocalized so that we can obtain meaningful information by a which-side measurement. Our numerical procedure provides a precise way to calculate the wave function throughout the process, from which one can estimate the amount of this information for an arbitrary insertion protocol.

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。

↑