开发用于量子计算的一体式离子阱

The promise of quantum computation is that it can calculate or simulate certain difficult and important problems much more efficiently than the classical computation counterpart. The ion trap system fulfills essential requirements of the full scale quantum computer, which shows there is no fundamental limitation to implement it. One remaining challenge is to miniaturize the trap structure to realistically scale up the ion trap quantum computer. We propose to develop a 3D monolithic ion trap that combines the advantage of 3D traps, a deep confining potential, and 2D surface traps, amenable to microfabrication as a monolithic structure. The manufacture of the 3D monolithic trap will accelerate the progress toward the large scale quantum computation with trapped ions. In the proposal, we plan to achieve the following mile stones. First, we use Yb+ atomic ion system for the test of the proposed trap. Yb+ system is attractive atomic species, which show reasonably good performance of basic quantum operations: i) initialization by standard optical pumping, ii) detection by quantum jump technique, iii) near ideal qubit rotation by resonant microwave and long coherence time. We establish the coherent quantum operation by Raman laser scheme that resolves motional sidebands, which enable us to measure the trap frequency and decoherence of the motional degree of freedom. Second, we investigate the design of 3D monolithic ion trap that is analogous to the combination of the three-layer trap and the symmetric trap. We miniaturize the standard bulk ion trap in an order of magnitude, which increases the trap frequency and stability. As a first try, we consider 20 DC electrodes, which is able to produce a uniformly spaced ion chain for the scalable quantum computation. Third, we manufacture the trap on a laser-machined alumina plate with gold coating, which has been successfully used for trapping ions. Since the whole trap will be made of one substrate, the post-processing assembly of multi-layers is not required, which makes the trap technology be extended to implement a junction structure to transport ions between different confining zones.

量子计算的最大亮点表现在计算或者模拟某些困难但是很重要的问题时，它会比相应的经典计算高效许多。现有的离子阱系统满足实现全功能量子计算机的所有必要需求，因此基于它来实现真正的量子计算机其实已经没有本质上的限制。但目前尚存的挑战之一是小型化离子阱的结构，以便在实用中扩大离子阱量子计算机的规模。我们计划开发一个3维一体式离子阱，它能集目前3维离子阱与2维离子阱之所长，即既能像3维离子阱一样有很深的势阱，又能像2维平面离子阱一样，便于通过微加工加工成一体式结构。3维一体式离子阱的投产必将大大加速基于离子阱的大规模量子计算机的发展进程。 本计划中设定了如下里程碑目标： 1.用Yb+离子系统来测试3维一体式离子阱； 2.从三层阱与对称阱的组合设计出发来研究3维一体式离子阱的最优设计； 3.在激光微加工氧化铝陶瓷基板上通过金带压焊等工艺加工3维一体式离子阱成品。

在过去的四年中，我们最终完成了项目的预定目标，在此过程中我们遇到了许多意料之外的困难，但我们都一一克服，并在项目时间内完成了目标。此项目的目标是开发一种新型的离子阱，使得这种离子阱能够稳定的囚禁多个离子，并且具有适用于量子计算的囚禁频率。为了完成这个目标，我们制定了三个子目标，从而让我们能够在四年内完成整体项目：1. 搭建用于囚禁离子的激光系统。2. 探索和确定一体式离子阱的设计。3. 制造和测试一体式离子阱。.在这四年中，我们搭建了用于囚禁Yb离子的激光系统，为了更快地测试，我们甚至还搭建了用于囚禁Ba离子的激光系统。我们设计并制造了一体式离子阱，在经过几轮的测试、实验和修改后，我们成功的在我们的新型离子阱中囚禁了多个Yb离子和Ba离子，甚至完成了不同种离子的同时囚禁。我们用Yb离子测试和标定了囚禁频率和我们控制的DC以及RF电压之间的关系，测试了离子阱的加热率以及离子的囚禁寿命。我们还将测量结果和数值模拟结果进行了比较，获得了完美的匹配。.我们的项目属于基础科学研究，大部分研究成果都发表于学术期刊。在四年中，我们通过此项目的支持一共发表了13篇SCI收录文章，包括1篇文章发表于Nature Photonics、1篇文章发表于Nature Physics，4篇文章发表于Nature Communications，1篇文章发表于Proceedings of the National Academy of Sciences，2篇文章发表于Physical Review Letters。1位博后和10位博士生参与了这个项目。在此项目期间，四位博士生完成了学位，一位硕士生完成了学位。