基于固态自旋量子比特的高保真度量子逻辑门的实验研究

发布时间：2018-08-18 14:09

【摘要】：量子计算作为一种新型的信息处理方式,利用量子力学的原理,能够有效处理如大数分解等很多经典计算难以解决的问题。要实现实用的大规模量子计算,需要通过纠错编码的方式实现容错量子计算,这要求实现的量子逻辑门的保真度高于某个容错阈值。容错阈值对量子逻辑门的保真度的要求是很苛刻的,以surface code为例,一般认为其要求量子逻辑门的保真度需达到0.99以上。而物理体系的量子特性极易受到噪声的影响,如何在噪声影响下实现高保真度的量子逻辑门,成为很多体系实现量子计算的一个重大挑战。我们基于量子计算的一个重要候选体系——金刚石NV色心,实验研究能够抑制噪声进而实现高保真度量子逻辑门的方法,并在金刚石NV色心体系实现了保真度高达0.99995的单比特量子逻辑门和保真度0.992的两比特量子逻辑门。这些量子逻辑门保真度不仅达到了 surface code对保真度的阈值要求,而且是目前为止固态自旋体系量子逻辑门保真度的最高水平。本论文的主要内容是介绍我们在金刚石NV色心体系进行高保真度量子逻辑门的实验研究的主要成果,主要包括以下三个工作:1.实验验证和实现动力学纠错量子逻辑门。我们通过动力学纠错量子逻辑门,国际上首次将实现量子逻辑门过程中对噪声的抑制水平达到6阶,并将可用于施加量子逻辑门的相干时间突破T_2极限,达到T_(1ρ)极限。2.实现保真度达到容错阈值要求的普适量子逻辑门。我们发展了新型组合脉冲、最优控制、波形校准等方法和技术,在室温大气下~(13)C自然丰度的金刚石中的NV色心体系实现了保真度高达0.99995的单比特量子逻辑门和保真度0.992的两比特量子逻辑门。3.实验实现时间最优的普适量子逻辑门。我们将量子最速降线方程应用于金刚石NV色心体系,国际上首次以时间最优的方式实现了普适量子逻辑门,实现的量子逻辑门不仅保真度高达0.99,而且时间比常规方法显著缩短。
[Abstract]:As a new information processing method, quantum computing can effectively deal with many difficult problems such as large number decomposition and so on by using the principle of quantum mechanics. In order to realize the practical large-scale quantum computation, it is necessary to implement the fault-tolerant quantum computation by error correcting coding, which requires the fidelity of the quantum logic gates to be higher than a certain fault-tolerant threshold. Fault-tolerant threshold is very strict to the fidelity of quantum logic gates. Taking surface code as an example, it is generally considered that the fidelity of quantum logic gates should be above 0.99. However, the quantum properties of physical systems are easily affected by noise. How to realize high fidelity quantum logic gates under the influence of noise has become a major challenge for many systems to realize quantum computing. Based on diamond NV color center, an important candidate system for quantum computing, we have studied experimentally the method of suppressing noise and realizing high fidelity quantum logic gate. A single-bit quantum logic gate with a fidelity of up to 0.99995 and a two-bit quantum logic gate with a fidelity of 0.992 are realized in the diamond NV color center system. The fidelity of these quantum logic gates not only meets the threshold requirements of surface code for fidelity, but also is the highest level of fidelity of quantum logic gates in solid-state spin systems so far. The main content of this thesis is to introduce the main results of our experimental research on high fidelity metric sub-logic gate in diamond NV color center system, including the following three works: 1. Experimental verification and implementation of dynamic error correction quantum logic gate. By means of dynamic error correction quantum logic gate, the noise suppression level in the realization of quantum logic gate is 6 order in the world for the first time, and the coherence time which can be used to apply quantum logic gate breaks through T2 limit and reaches T _ (1 蟻) limit. 2. Universal quantum logic gates with fidelity up to the threshold of fault tolerance are realized. We have developed new methods and techniques such as combined pulse, optimal control, waveform calibration, etc. The NV color center system in diamond with natural abundance of ~ (13) C at room temperature has achieved single-bit quantum logic gates with fidelity up to 0.99995 and two-bit quantum logic gates with fidelity 0.992. The universal quantum logic gate with optimal time is realized experimentally. In this paper, we apply quantum steepest descent line equation to diamond NV color center system. The universal quantum logic gate is realized in the world for the first time in a time-optimal manner. The realized quantum logic gate not only has a fidelity of up to 0.99, but also shortens the time significantly compared with the conventional method.
【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O413

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