Neutron Interferometry and Neutron Schrodinger Wave Optics

中子干涉仪是一种利用自由中子的量子力学（QM）波状特性来非常精确地测量自然某些特性的设备。它的功能很像光学干涉仪，只不过它探测的是中子“波”而不是光波的干涉。一个慢中子（速度小于2000米/秒）有一个相关的量子点波长，其大小与固体中原子的间距相当，因此它与物质的相互作用是相干的，即像波而不是粒子。当一个慢中子进入干涉仪时，它的QM波在一个完美的硅晶体中衍射，并分裂成两个子波，每个子波走不同的路径。然后，这两个子波撞击第二个硅晶体，并再次衍射成四个子波，它们仍然与原来的单个中子有关。这四个子波中的两个在第三个硅晶体中再次相遇，并且可以相互干扰。干涉的程度决定了放置在干涉仪后面的中子探测器探测到中子的概率。我们可以在干涉仪内放置一块物质，一个磁场或电场，甚至一个引力场，以改变一个子波相对于另一个子波的相位，从而改变这种干涉。通过观察中子探测率的变化，我们精确地测量了相移的量。这提供了关于中子在材料或场中相互作用的强度和性质的重要且通常是独特的信息。在一个实验中，我们在硅晶体中挑出了中子与电子相互作用引起的相移。总的来说，中子是电中性的，但由于它的磁矩和它含有带电夸克，它确实能感受到来自带电粒子（如电子）的力。我们的测量将使我们对中子内部电荷的分布有更好的了解。在另一个实验中，我们精确测量了由于中子与氦的稀有轻同位素He-3相互作用而产生的相移，以及当中子的自旋方向与He-3原子核的自旋方向相同或相反时相移是如何变化的。这将提供原子核内中子和质子之间作用力性质的重要细节。第三个实验使用漂浮在溴化锌溶液中的特殊中子干涉仪来测量中子在地球引力场中的相移。我们将尝试解决过去这种类型的中子实验与爱因斯坦弱等效原理之间长期存在的差异，该原理指出粒子的引力质量和惯性质量相等。

The neutron interferometer is a device that uses the quantum mechanical (QM) wave-like properties of free neutrons to measure certain properties of nature very precisely. It functions much like an optical interferometer, except that it detects the interference of neutron "waves" rather than light waves. A slow neutron (speed less than about 2000 m/s) has an associated QM wavelength comparable in size to the spacing of atoms in a solid, so it interacts with matter coherently, i.e. like a wave rather than a particle.When a slow neutron enters the interferometer, its QM wave is diffracted in a perfect silicon crystal and splits into two sub-waves, each taking a different path. These two sub-waves then strike a second silicon crystal and are diffracted again, into four sub-waves, all still associated with the original single neutron. Two of these four sub-waves meet again in a third silicon crystal and can interfere with each other. The degree of interference determines the probability of detecting the neutron in a neutron detector placed behind the interferometer. We can place a piece of matter, a magnetic or electric field, or even a gravitational field inside the interferometer to shift the phase of one sub-wave relative to another and change this interference. By noting the resulting change in the neutron detection rate we precisely measure the amount of phase shift. This gives important and often unique information about the strength and nature of the neutron's interaction in the material or field.In one experiment, we single out the neutron phase shift caused by its interactions with electrons in a silicon crystal. Overall the neutron is electrically neutral, but it does feel a force from charged particles such as electrons because of its magnetic moment, and because it contains charged quarks. Our measurement will lead to a much better understanding of the internal charge distribution in the neutron. In another experiment, we precisely measure the phase shift due to the neutron's interaction with He-3, a rare light isotope of helium, and how it changes when the neutron's spin direction is made the same or opposite to the spin direction of the He-3 nuclei. This will provide important details about the nature of the force between neutrons and protons inside atomic nuclei. A third experiment measures the neutron's phase shift in the Earth's gravitational field using a special neutron interferometer that floats in a zinc bromide solution. We will try to resolve a long-standing discrepancy between past neutron experiments of this type and Einstein's Weak Equivalence Principle, which states that a particle's gravitational and inertial masses are equal.