Quantum logic gates using Stark shifted Raman transitions in a cavity

光学腔中铷原子超辐射拉曼散射的理论研究

Theoretical Study on Superradiant Raman Scattering with Rubidium Atoms in An Optical Cavity

本研究通过量子主方程理论，将铷原子视为三能级系统并与光学腔耦合，统一解释了超辐射拉曼散射脉冲及稳态宽谱现象，为超辐射激光及相关量子现象研究提供了理论工具。

Two-dimensional sideband Raman cooling and Zeeman state preparation in an optical lattice

A method of sideband Raman cooling to the vibrational ground state of the $m=0$ Zeeman sublevel in a far-detuned two-dimensional optical lattice is proposed. In our scheme, the Raman coupling between vibrational manifolds of the adjacent Zeeman sublevels is shifted to the red sideband due to the ac Stark effect induced by a weak pump field. Thus, cooling and optical pumping to $m=0$ is achieved by purely optical means with coplanar cw laser beams. The optical lattice and cooling parameters are estimated in the framework of simple theoretical models. An application of the transverse sideband co…

Realization of the Dicke model using cavity-assisted Raman transitions

We realize an open version of the Dicke model by coupling two hyperfine ground states using two cavity-assisted Raman transitions. The interaction due to only one of the couplings is described by the Tavis-Cummings model and we observe a normal mode splitting in the transmission around the dispersively shifted cavity. With both couplings present the dynamics are described by the Dicke model and we measure the onset of superradiant scattering into the cavity above a critical coupling strength.

Cavity-stimulated Raman emission from a single quantum dot spin

Solid state quantum emitters have shown strong potential for applications in quantum information, but spectral inhomogeneity of these emitters poses a significant challenge. We address this issue in a cavity-quantum dot system by demonstrating cavity-stimulated Raman spin flip emission. This process avoids populating the excited state of the emitter and generates a photon that is Raman shifted from the laser and enhanced by the cavity. The emission is spectrally narrow and tunable over a range of at least 125 GHz, which is two orders of magnitude greater than the natural linewidth. We obtain t…

All-optical tuning of a quantum dot in a coupled cavity system

We demonstrate a method of tuning a semiconductor quantum dot (QD) onto resonance with a cavity mode all-optically. We use a system comprised of two evanescently coupled cavities containing a single QD. One resonance of the coupled cavity system is used to generate a cavity enhanced optical Stark shift, enabling the QD to be resonantly tuned to the other cavity mode. A twenty-seven fold increase in photon emission from the QD is measured when the off-resonant QD is Stark shifted into the cavity mode resonance, which is attributed to radiative enhancement of the QD. A maximum tuning of 0.06 nm …

Silent-enhancement of multiple Raman modes via tuning optical properties of graphene nanostructures

Raman scattering signal can be enhanced through localization of incident field into sub-wavelength hot-spots through plasmonic nano-structures (Surface-enhanced Raman scattering-SERS). Recently, further enhancement of SERS signal via quantum objects are proposed by [1] without increasing the hot-spot intensity (\textit{silent-enhancement}) where this suggestion prevents the modification of vibrational modes or the breakdown of molecules. The method utilizes path interference in the non-linear response of Stokes-shifted Raman modes. In this work, we extend this phenomenon to tune the spectral p…

用于量子信息处理的激光束轮廓的离子表征

Ion-Based Characterization of Laser Beam Profiles for Quantum Information Processing

该研究提出利用囚禁离子作为传感器，通过四光子斯塔克位移效应直接表征量子门操作所需的激光束，优化激光参数以实现更高速、低错误率的拉曼驱动门，为提升系统性能提供反馈。

Multiphoton Raman transitions and Rabi oscillations in driven spin systems

In the framework of the non-secular perturbation theory based on the Bogoliubov averaging method, the coherent dynamics of multiphoton Raman transitions in a two-level spin system driven by an amplitude-modulated microwave field is studied. Closed-form expressions for the Rabi frequencies of these transitions have been obtained beyond the rotating wave approximation for the low-frequency driving component. It is shown that spin states dressed by the high-frequency component of the driving field are shifted due to the Bloch-Siegert-like effect caused by antiresonant interactions with the strong…

Off-axis optical vortices using double-Raman singlet and doublet light-matter schemes

We study the formation of off-axis optical vortices propagating inside a double-Raman gain atomic medium. The atoms interact with two weak probe fields as well as two strong pump beams which can carry orbital angular momentum (OAM). We consider a situation when only one of the strong pump lasers carries an OAM. A particular superposition of probe fields coupled to the matter is shown to form specific optical vortices with shifted axes. Such off-axis vortices can propagate inside the medium with sub- or superluminal group velocity depending on the value of the two-photon detuning. The superlumi…

法拉第光学控制量子点自旋中从拉比振荡到绝热布居转换的交叉

Crossover from Rabi oscillations to adiabatic population switching in the Faraday optical control of quantum dot spins

通过研究法拉第几何中受激拉曼跃迁的斯塔克位移振荡，揭示了从拉比振荡到绝热布居转换的连续交叉机制，并利用Landau-Zener-Stückelberg干涉实现了阶梯式布居反转。

All optical quantum storage based on spatial chirp of the control field

We suggest an all-optical quantum memory scheme which is based on the off-resonant Raman interaction of a signal quantum field and a strong control field in a three-level atomic medium in the case, when the control field has a spatially varying frequency across the beam, called a spatial chirp. We show that the effect of such a spatial chirp is analogous to the effect of a controllable reversible inhomogeneous broadening (CRIB) of the atomic transition used in the gradient echo memory (GEM) scheme. However, the proposed scheme does not require temporal modulation of the control field or the at…

Prospects for the cavity-assisted laser cooling of molecules

Cooling of molecules via free-space dissipative scattering of photons is thought not to be practicable due to the inherently large number of Raman loss channels available to molecules and the prohibitive expense of building multiple repumping laser systems. The use of an optical cavity to enhance coherent Rayleigh scattering into a decaying cavity mode has been suggested as a potential method to mitigate Raman loss, thereby enabling the laser cooling of molecules to ultracold temperatures. We discuss the possibility of cavity-assisted laser cooling particles without closed transitions, identif…

QUPERS：量子增强拉曼光谱

QUPERS: Quantum Enhanced Raman Spectroscopy

本文实验演示了量子点与金属纳米颗粒耦合引发的路径干涉（Fano）效应，使 SERS 在传统增强基础上额外获得 7 倍增强因子，并提出通过外场调控量子点共振实现拉曼谱带选择性增强的新方案。