Testing the Symmetrization Principle with a Pair of Trapped Ions

量子物理学引入了这样一种概念，即两个或多个物体，如电子或质子，可以是不可区分的，也就是说，它们没有任何属性可以让人们区分它们。虽然这一思想的数学结果构成了我们所知的所有物质（如原子核和原子）稳定性的基础，但很难直接证明两个物体是真正不可区分的。为此，必须创建一种情况，其中两个（或更多）不可区分的对象同时存在于每个位置。这种情况发生在分子中，导致分子不吸收和发射某种颜色的光。该项目将通过可控地交换间隔10微米的多个钙离子的位置，将这种效应从原子尺度带到更人性化的长度尺度（相当于人类头发的直径）。在非常受控的条件下，在相对较大的长度尺度上证明这一重要的量子效应，不仅将在新的参数范围内测试量子力学的原理，而且还将量子物理学带到人类感官可及的尺度，从而启发学生以及公众。这个项目的目标是证明两个量子粒子之间的干涉与个别单-粒子波函数永远不会重叠为此，两个钙-40离子将以快速旋转的量子态制备。激光脉冲将角动量传递给离子串，从而将其分裂成两个波包。在两个波包相对于彼此旋转180度之后，它们将再次与第二光脉冲组合。这一过程会使一种离子与另一种离子相互干扰，反之亦然。以前没有证明离子可以相互干扰。该项目旨在表明，即使离子总是相隔几微米，也可以使它们无法区分。这种不寻常的情况导致两个单粒子波函数之间的重叠消失，使研究人员能够通过直接测量粒子交换下的相位来对交换原理进行受控测试。因此，验证费米子钙-40离子在粒子交换下获得-1的相位因子变得可行。最后，该项目将研究在何种情况下两种离子仍然无法区分，从而阐明实际上可以区分相同粒子的过程类型。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Quantum physics introduces the notion that two or more objects, such as electrons or protons, can be indistinguishable, i.e. they have no properties which would allow one to tell them apart. While the mathematical consequences of this idea form the basis of the stability of all matter we know of, such as nuclei and atoms, it is very difficult to directly verify that two objects are truly ndistinguishable. For this, one must create a situation where two (or more) indistinguishable objects exist at each location at the same time. Such a scenario occurs in molecules, causing the molecule to not absorb and emit light of a certain color. This project will bring this effect from the atomic scale to a more human length scale (comparable to the diameter of human hair) by controllably exchanging the position of multiple Calcium ions spaced 10 micrometers apart. The demonstration of this important quantum effect under very controlled conditions over relatively large length scales will not only test the principles of quantum mechanics in a new parameter regime, but also bring quantum physics to scales accessible to human senses, thereby inspiring students as well as the general public.The goal of this project is to demonstrate interference between two quantum particles with individual single-particle wavefunctions that never overlap. For this, two Calcium-40 ions will be prepared in a quickly rotating quantum state. A laser pulse will impart angular momentum to the ion string, thereby splitting it into two wavepackets. After the two wavepackets have rotated with respect to each other by 180 degrees, they will be combined again with a second light pulse. This procedure interferes one ion with the other and vice versa. It has not been previously demonstrated that ions can interfere with each other. This project aims at showing that ions can be made indistinguishable, even if they are always separated by several micrometers. This unusual situation leads to a vanishing overlap between the two single-particle wavefunctions, allowing the researchers to conduct a controlled test of the exchange principle by directly measuring the phase under particle exchange. Thus it becomes feasible to verify that the fermionic Calcium-40 ions acquire a phase factor of -1 under particle exchange. Finally, the project will study under which circumstances the two ions remain indistinguishable, thereby shedding light on the types of processes which actually can distinguish between identical particles.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.