量子隧穿时间与脉冲传播的负时延

为了计算粒子隧穿通常认为是禁区的势垒的时间,应考虑波包的传输。这被许多科学家(如MacColl、Wigner、Hartman、Büttikar等)讨论过。按照Hartman的解析表达式,隧穿时间是非零的正值;而对于较厚的势垒,传输时间与垒厚无关。这为粒子的超光速运动提供了理论上的可能性。1960年L.Brillouin讨论了色散媒质中的光传播,结果认为信号速度vs与群速vg并无不同,除非在反常色散区。vg可以比真空中光速大(vgc),甚至变为负值(vg0)。这样就使人们对波传播中的负时延产生了兴趣。但Brillouin说"负群速(NGV)没有物理意义",现在我们知道这样讲是错误的。本文着重研究了负群速特征(NGVF);首先指出存在两种情况:空间中的反向运动和对时间的反向运动。指出在波动力学中波速度(例如vp、vg)是标量,故NGV的含义并非仅为"运动方向反了过来"。其次指出NGV波是超前波,它不仅比真空中光速c快,而且快到在完全进入媒质前就离开了媒质。电磁脉冲可以作时间超前运动是一种负性运动。这种现象对物理学家而言很重要,因为他们想知道究竟发生了什么。最后给出了我们使用互补类Ω结构(COLS)构成的左手传输线的微波脉冲传输特性的实验研究。在(5.6~6.1)GHz形成阻带,其中状态为反常色散。获得了NGV特征,即脉冲超前传播——输入脉冲峰进入样品前输出脉冲峰即在出口浮现。获得了负群速,vg=(-0.13 c)~(-1.85 c)。

Quantum Tunneling Time and Negative Time-Delay in Pulse Propagation

Abstract： To account for the time spent by a tunneling particle in the classically forbidden region of a po- tential barrier, the transmission of a wave-packet must be considered. This problem was discussed by Mac- Coll, Wigner, Hartman, Bfittikar and other scientists. According to the Hartman＇s analytic expressions, the tunneling time is positive, non zero; and for thicker barriers, the transmission time is independent of barrier thickness. It is the theoretical possibility of superluminal motion of the particle.In 1960, L.Brillouin discussed the propagation of light in dispersive media. The results can be summarized in the following viewpoints： The signal velocity vs does not differ from the group velocity vg, except in the region of anomalous dis- persion. The vg can greater than the light velocity in vacuum（vg 〉 c）, and it even becomes negative （Vg 〈 0）. Then, considerable interest has developed on negative time-delay in wave propagation. But, Brillouin said： ＂The negative group velocity （NGV） has no physical meaning＂, now we know this idea is wrong. In this paper we study the features of negative group velocity, i.e. the NGV Features （NGVF）; Firstly, it contains two situations： backward motion in space and backward motion in time. We must remember that, in the Wave Mechanics the wave velocity （such as vp and we）is scalar, so NGV does not only indi- cate the direction of movement is flow backward. Secondly, the NGV- wave is advanced wave, it is not only faster than a wave traveling in vacuum by c, and so quickly that it left the medium before it had even finished entering. The electro-magnetic pulse can moving advanced in time, it is a negative characteris- tic motion. This phenomenon is of great importance to physicist, they will be interested to know what hap- pens. Finally, In this paper, the microwave pulse propagation transferred through a left-handed transmission line using Complementary Omega-Like Structures（COLS） loaded was studied. There was a stop band in transmission from 5.6GHz to 6.1GHz, and the anomalous dispersion was causes in this band. Negative group velocity corresponds to the case in which the peak of the pulse exited before the peak of the incident pulse had entered the sample. The negative group velocity reached （-0.13c）-（-1.85C）o