测量对不稳定系统寿命和线宽的影响
Influence of measurement on the life-time and the line-width of unstable systems
摘要：
研究了电子隧穿出量子点的量子芝诺效应。结果表明，整个系统的薛定谔方程可以简化为描述探测器和被测系统的组合时间发展的布洛赫型速率方程。利用这些方程，我们发现不稳定系统的连续测量不影响其指数衰减到具有恒定态密度的库。然而，隧穿电子的能量分布的宽度不等于寿命的倒数--它由于探测器产生的退相干而增加。我们扩展的分析的情况下，由能量依赖的态密度描述的水库，我们表明，连续测量这样的量子系统的影响的指数衰减率和能量分布。衰变并不总是减慢，但可能会加速。隧穿电子的能量分布可以揭示测量前不可见的谱线。
英文摘要：
We investigate the quantum Zeno effect in the case of electron tunneling out of a quantum dot in the presence of continuous monitoring by a detector. It is shown that the Schrödinger equation for the whole system can be reduced to Bloch-type rate equations describing the combined time-development of the detector and the measured system. Using these equations we find that continuous measurement of the unstable system does not affect its exponential decay to a reservoir with a constant density of states. The width of the energy distribution of the tunneling electron, however, is not equal to the inverse life-time -- it increases due to the decoherence generated by the detector. We extend the analysis to the case of a reservoir described by an energy dependent density of states, and we show that continuous measurement of such quantum systems affects both the exponential decay rate and the energy distribution. The decay does not always slow down, but might be accelerated. The energy distribution of the tunneling electron may reveal the lines invisible before the measurement.
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