从分数量子霍尔效应到拓扑量子计算

分数量子霍尔效应系统是奇异的量子液体,其中的准粒子激发可以带分数电荷,甚至具有非阿贝尔的统计性质。理论研究表明,这些准粒子可以用来实现在硬件上可容错的量子计算,即拓扑量子计算。文章在介绍分数量子霍尔效应及其在拓扑量子计算中的潜在应用基础上,重点回顾了近五年来对填充因子为5/2的分数量子霍尔态中非阿贝尔准粒子的实验探测和部分相关理论诠释。     

从分数量子霍尔效应到拓扑量子计算*

分数量子霍尔效应系统是奇异的量子液体,其中的准粒子激发可以带分数电荷,甚至具有非阿贝尔的统计性质。理论研究表明,这些准粒子可以用来实现在硬件上可容错的量子计算,即拓扑量子计算。文章在介绍分数量子霍尔效应及其在拓扑量子计算中的潜在应用基础上,重点回顾了近五年来对填充因子为5/2的分数量子霍尔态中非阿贝尔准粒子的实验探测和部分相关理论诠释。     

Disorder and the fractional quantum Hall effect

The fractional quantum Hall effect is studied in the 2D electron gas of four GaAs-Al_xGa_1?xAs heterostructures. Localization due to disorder, known to give rise to the wide integral quantum Hall plateaus, is demonstrated to inhibit the fractional effect, which is observed only in the higher mobility samples.     

Topology and fractional quantum Hall effect

Starting from Laughlin-type wave functions with generalized periodic boundary conditions describing the degenerate ground state of a quantum Hall system we explicitly construct r-dimensional vector bundles. It turns out that the filling factor ν is given by the topological quantity c₁/r where c₁ is the first Chem number of these vector bundles. In addition, we managed to proof that under physical natural assumptions the stable vector bundles correspond to the experimentally dominating series of measured fractional filling factors ν = n/(2pn±1). Most remarkably, due to the very special form of the Laughlin wave functions the fluctuations of the curvature of these vector bundles converge to zero in the limit of infinitely many particles which shows a new mathematical property. Physically, this means that in this limit the Hall conductivity is independent of the boundary conditions which is very important for the observability of the effect. Finally, we discuss the relation of this result to a theorem of Donaldson.     

Geometrical description of the fractional quantum Hall effect

The fundamental collective degree of freedom of fractional quantum Hall states is identified as a unimodular two-dimensional spatial metric that characterizes the local shape of the correlations of the incompressible fluid. Its quantum fluctuations are controlled by a topologically quantized "guiding-center spin." Charge fluctuations are proportional to its Gaussian curvature.     

Quark confinement and the fractional quantum Hall effect

Working in the physics of Wilson factor and Aharonov-Bohm effect, we find in the fluxtube-quark system the topology of a baryon consisting of three heavy flavor quarks resembles that of the fractional quantum Hall effect (FQHE) in condensed matter. This similarity yields the result that the constituent quarks of baryon have the ``filling factor' 1/3, thus the previous conjecture that quark confinement is a correlation effect is confirmed. Moreover, by deriving a Hamiltonian of the system analogous to that of FQHE, we predict an energy gap for the ground state of a heavy three-quark system.     

Quark confinement and the fractional quantum Hall effect

Working in the physics of Wilson factor and Aharonov-Bohm effect,we find in the fluxtubequark system the topology of a baryon consisting of three heavy flavor quarks resembles that of the fractional quantum Hall effect(FQHE)in condensed matter.This similarity yields the result that the constituent quarks of baryon have the"filling factor"1/3.thus the previous conjecture that quark confinement is a correlation effect is confirmed.Moreover,by deriving a Hamiltonian of the system analogous to that of FQHE,we predict an energy gap for the ground state of a heavy three-quark system.