Ion-Trap-Based Quantum Computers: From Benchmarking to Outperforming Classical Digital Computers

我们对量子物理学的应用开始于世纪之交，当时科学家们开始探索原子和电子的超小世界。虽然量子力学的大部分理论基础是在20世纪20年代制定的，但我们仍然没有采用重要的技术来考虑量子世界可能产生的奇异行为（如隐形传态或量子干涉）。最近，在一种新的计算范式中有了重大进展，称为量子计算。它的操作基于其组成部分之间的量子力学效应，它可以开创一个新的计算领域-一个小型量子计算机可以容纳比以往任何时候都建造（或将要建造）的传统计算机更多的内存，或者它可以快速解决困难的问题，比如找到大数的素因子，从而打破我们目前的加密标准。虽然我们还没有商店里的“微软量子表面”设备，但研究实验室已经生产出了所谓的量子模拟器，它模拟耦合量子系统的行为，并允许在计算结束时读取它们的属性。该研究项目将致力于寻找方法来验证这些量子计算机的正确性，当它们超越传统计算机的能力时。这是通过寻找特殊情况来实现的，在这些情况下，传统计算机可以预测结果，并确定如何在这些特殊情况下运行量子计算机。除了拟议的研究工作外，该项目还有一个重要的推广部分，该小组将于2016年秋季在EdX上推出一个名为“人人适用的量子力学”的大规模开放式在线课程（MOOC），该课程将以最少的数学知识教授量子力学原理。（不比平方根复杂），并配有一系列交互式计算机演示、教程和插图。本书将探讨三个主题：（1）通过观察两种自旋压缩效应，检查晶格振动对基于离子阱的量子模拟器的性能的影响（其中海森堡不确定性原理可以部分击败）和计算中的长程相互作用的限制;（二）确定将量子计算从几十KHz的时钟频率加速到可以推到MHz范围内的时钟频率的技术，进一步;以及（3）发现宏观量子隧穿效应或脆弱量子态（如所谓的NOON态）是否可以在这些量子模拟器中形成和使用。我们使用的量子模拟器类型是由被捕获的离子组成的，这些离子由激光驱动，激光对离子施加自旋相关的力（其中自旋自由度通常是离子的超精细状态）。激光根据离子的内部量子态推动离子，而与晶格振动的耦合驱动这些内部状态之间的后续耦合。通过适当地设计这些耦合，可以创建量子计算机/模拟器。这项理论工作将与NIST博尔德（潘宁阱）、马里兰州（线性保罗阱）和加州大学洛杉矶分校（平面保罗阱）的实验工作密切配合。

Our use of of quantum physics began around the turn of the 20th century, when scientists started exploring the ultrasmall world of atoms and electrons. While much of the theoretical basis for quantum mechanics was worked out in the 1920's, we still do not employ significant technologies that take into account the bizarre behaviors that are possible due to the quantum world (like teleportation or quantum interference). Recently, there has been significant advance in a new paradigm for computing, called quantum computing. With its operation based on the quantum-mechanical effects between its constituents, it can usher in a new realm of computation--where a small quantum computer can hold more memory than that of every conventional computer ever built (or to be built), or it can rapidly solve hard problems like finding the prime factors of large numbers and thereby breaking our current standards for encryption. While we don't yet have the "Microsoft quantum surface" devices available in stores, research labs have produced so-called quantum simulators, which emulate the behavior of coupled quantum systems and allow their properties to be read off at the end of the computation. This research project will work on finding ways to verify the correctness of these quantum computers when they surpass the abilities of conventional computers. This is done by finding special cases, where conventional computers can predict the results, and determining how to run the quantum computers for those special cases. In addition to the research work proposed, this project has a significant outreach component, where the group will be launching a Massive Open Online Course (MOOC) entitled "Quantum mechanics for everyone" on EdX in the fall of 2016, which will teach quantum mechanics principles with minimal math (no more complicated than taking square roots) and with a series of interactive computer demonstrations, tutorials, and illustrations.Three main themes will be pursued in this work: (1) Examining effects of the lattice vibrations on the performance of ion-trap-based quantum simulators by looking at both spin squeezing effects (where the Heisenberg uncertainty principal can be partially beaten) and on computation in the long-range interacting limit; (2) Determining techniques to speed up quantum computation from clock frequencies in the 10s of KHz to clock frequencies that can be pushed in the MHz range or further; and (3) Discovering whether macroscopic quantum tunneling effects, or fragile quantum states (like the so-called NOON states) can be formed and employed in these quantum simulators. The type of quantum simulator we work with is one that is built out of trapped ions that are driven by lasers that apply spin-dependent forces on the ions (where the spin degree of freedom is often a hyperfine state of the ion). The lasers push the ions according to their internal quantum states, while the coupling to the lattice vibrations drives a subsequent coupling between those internal states. By properly engineering these couplings, one creates a quantum computer/simulator. This theoretical work will pair closely with experimental work at NIST Boulder (Penning trap), Maryland (linear Paul trap), and UCLA (planar Paul trap).