共查询到20条相似文献,搜索用时 843 毫秒
1.
2.
3.
4.
5.
6.
基于一维水平光晶格的锶原子光晶格钟实验平台,当系统的稳定度和不确定度达到10-18量级以上时,由量子隧穿效应引起的钟频移变得不容忽视.在浅光晶格中,量子隧穿效应会使钟跃迁谱线发生明显的展宽现象,因此,本文通过研究浅光晶格中的量子隧穿现象,为87Sr原子光晶格钟系统不确定度的评估奠定基础.本实验在一维87Sr原子光晶格钟平台上,利用超稳超窄线宽的698 nm激光激发87Sr冷原子~lS0(|g>)→~3P0(|e>)跃迁(即钟跃迁),实现了对锶原子分布在特定量子态的制备.在深光晶格中,将原子制备到|e,nz=1>态后,再绝热地降低光晶格阱深,然后在浅光晶格中,探测激发态的载波-边带可分辨的钟跃迁谱线.从钟跃迁谱线中观测到载波谱线发生了明显的劈裂,表明原子在光晶格相邻格点间产生了明显的量子隧穿现象.通过对光晶格中量子隧穿机制的理解,不仅有利于提高光晶格钟的不确定度,也可为观测光晶格中费米子的自旋轨道耦合效应提供基础数据. 相似文献
7.
8.
9.
10.
线性响应理论是现代物理实验尤其是量子物态测量实验的理论基础,其核心是将物理系统的探测信号作为微扰,利用系统在未受扰动时的关联函数来刻画物理可观测量的响应.半个多世纪以来,基于封闭量子系统的线性响应理论在量子物态测量实验上取得了巨大的成功.随着超冷原子实验在光场与系统相互作用精确操控方面的快速进展,近年来高精度的冷原子实验已经具备研究耗散量子多体系统的条件,新奇的物理现象在实验中层出不穷,这使得国内外研究者对量子开放系统及其非厄米物理的研究与日俱增.基于此,我们发展了一个量子开放系统的线性响应理论——非厄米线性响应理论.该理论将耗散带来的非厄米效应与量子噪声作为外部探测输入来探测量子系统的性质,并将实验可观测量的含时演化与系统未受扰动状态时的关联函数及其谱函数联系了起来,提供了区分正常物态和奇异物态的一种新手段,所得到的结果与最近冷原子系统实验的结果高度吻合.本文介绍了非厄米线性响应理论,并讨论该理论在量子多体系统以及具有时间反演对称性的量子系统中的应用. 相似文献
11.
M. Aidelsburger M. Atala S. Nascimbène S. Trotzky Y.-A. Chen I. Bloch 《Applied physics. B, Lasers and optics》2013,113(1):1-11
We present the experimental generation of large effective magnetic fields for ultracold atoms using photon-assisted tunneling in an optical superlattice. The underlying method does not rely on the internal structure of the atoms and, therefore, constitutes a general approach to realize widely tunable artificial gauge fields without the drawbacks of near-resonant optical potentials. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov–Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of one flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for non-interacting particles. We provide a local measurement of the phase acquired by single particles due to photon-assisted tunneling. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the effective magnetic field is directly revealed. 相似文献
12.
V. A. Kashurnikov A. V. Krasavin 《Journal of Experimental and Theoretical Physics》2010,111(2):180-183
An ultracold Fermi gas in an optical lattice with a parabolic potential is modeled by the quantum Monte Carlo method. The
gas density profile is calculated in the Hubbard model; it is shown that a domain with a density of one atom per site is formed
in the trap that corresponds to the Mott insulator state. The insulator phase is surrounded by a superfluid region occupying
the center of the trap, as well as its periphery. 相似文献
13.
Aidelsburger M Atala M Nascimbène S Trotzky S Chen YA Bloch I 《Physical review letters》2011,107(25):255301
We use Raman-assisted tunneling in an optical superlattice to generate large tunable effective magnetic fields for ultracold atoms. When hopping in the lattice, the accumulated phase shift by an atom is equivalent to the Aharonov-Bohm phase of a charged particle exposed to a staggered magnetic field of large magnitude, on the order of 1 flux quantum per plaquette. We study the ground state of this system and observe that the frustration induced by the magnetic field can lead to a degenerate ground state for noninteracting particles. We provide a measurement of the local phase acquired from Raman-induced tunneling, demonstrating time-reversal symmetry breaking of the underlying Hamiltonian. Furthermore, the quantum cyclotron orbit of single atoms in the lattice exposed to the magnetic field is directly revealed. 相似文献
14.
文章从超冷原子研究的视角出发,回顾了用“从下到上”的方案来开展量子模拟研究的历史.超冷原子作为宏观量子态,各个自由度精确可控,是量子模拟的绝佳平台.光晶格将冷原子物理和凝聚态物理融合起来,是其中最重要的技术之一,为超冷原子量子模拟提供了一个扎实的落脚点.近年来,关于拓扑量子模拟的研究日益兴起,成为超冷原子量子模拟新的重... 相似文献
15.
16.
Graphene has attracted enormous attention over the past years in condensed matter physics. The most interesting feature of graphene is that its low-energy excitations are relativistic Dirac fermions. Such feature is the origin of many topological properties in graphene-like physics. On the other hand, ultracold quantum gas trapped in an optical lattice has become a unique setting for quantum simulation of condensed matter physics. Here, we mainly review our recent work on quantum simulation of graphene-like physics with ultracold atoms trapped in a honeycomb or square optical lattice, including the simulation of Dirac fermions and quantum Hall effect with and without Landau levels. We also present the related experimental advances. 相似文献
17.
Krzysztof Jachymski Zbigniew Idziaszek 《The European physical journal. Special topics》2013,217(1):85-90
We examine the possibility to study the statistical properties of trapped ultracold bosons with light scattering. We derive general effective hamiltonian and show that the spectrum of scattered photons contains information about density-density correlations. As a specific example we discuss light scattering as a potential tool to probe the Mott transition in optical lattice and Anderson localization in incommensurate superlattice. 相似文献
18.
We study fermionic atoms of three different internal quantum states (colors) in an optical lattice, which are interacting through attractive on site interactions, U<0. Using a variational calculation for equal color densities and small couplings, |U|<|UC|, a color superfluid state emerges with a tendency to domain formation. For |U|>|UC|, triplets of atoms with different colors form singlet fermions (trions). These phases are the analogies of the color superconducting and baryonic phases in QCD. In ultracold fermions, this transition is found to be of second order. Our results demonstrate that quantum simulations with ultracold gases may shed light on outstanding problems in quantum field theory. 相似文献
19.
In order to investigate the quantum phase transitions and the time-of-flight absorption pictures analytically in a systematic way for ultracold Bose gases in bipartite optical lattices, we present a generalized Green’s function method. Utilizing this method, we study the quantum phase transitions of ultracold Bose gases in two types of bipartite optical lattices, i.e., a hexagonal lattice with normal Bose–Hubbard interaction and a d-dimensional hypercubic optical lattice with extended Bose–Hubbard interaction. Furthermore, the time-of-flight absorption pictures of ultracold Bose gases in these two types of lattices are also calculated analytically. In hexagonal lattice, the time-of-flight interference patterns of ultracold Bose gases obtained by our analytical method are in good qualitative agreement with the experimental results of Soltan-Panahi, et al. [Nat. Phys. 7, 434 (2011)]. In square optical lattice, the emergence of peaks at \(\left( { \pm \frac{\pi }{a}, \pm \frac{\pi }{a}} \right)\) in the time-of-flight absorption pictures, which is believed to be a sort of evidence of the existence of a supersolid phase, is clearly seen when the system enters the compressible phase from charge-density-wave phase. 相似文献
20.
Rom T Best T Mandel O Widera A Greiner M Hänsch TW Bloch I 《Physical review letters》2004,93(7):073002
We demonstrate quantum control over both internal and external quantum degrees of freedom in a high number of identical "chemical reactions," carried out in an array of microtraps in a 3D optical lattice. Starting from a Mott insulating phase of an ultracold atomic quantum gas, we use two-photon Raman transitions to create molecules on lattice sites occupied by two atoms. In the atom-molecule conversion process, we can control both the internal rovibronic and external center of mass quantum state of the molecules. The lattice isolates the microscopic chemical reactions from each other, thereby allowing photoassociation spectra without collisional broadening even at high densities of up to 2 x 10(15) cm(-3). 相似文献