Manipulating Synchronous Optical Signals with a Double $Λ$ Atomic Ensemble

Superradiant cascade emissions in an atomic ensemble via four-wave mixing

We investigate superradiant cascade emissions from an atomic ensemble driven by two-color classical fields. The correlated pair of photons (signal and idler) is generated by adiabatically driving the system with large-detuned light fields via four-wave mixing. The signal photon from the upper transition of the diamond-type atomic levels is followed by the idler one which can be superradiant due to light-induced dipole-dipole interactions. We then calculate the cooperative Lamb shift (CLS) of the idler photon, which is a cumulative effect of interaction energy.We study its dependence on a cylin…

Adiabatic Creation of Atomic Squeezing in Dark States vs. Decoherences

We study the multipartite correlations of the multi-atom dark states, which are characterized by the atomic squeezing beyond the pairwise entanglement. It is shown that, in the photon storage process with atomic ensemble via electromagnetically induced transparency (EIT) mechanism, the atomic squeezing and the pairwise entanglement can be created by adiabatically manipulating the Rabi frequency of the classical light field on the atomic ensemble. We also consider the sudden death for the atomic squeezing and the pairwise entanglement under various decoherence channels. An optimal time for gene…

超强光物质耦合机制下的腔光力学：由 Casimir 力矩介导的自对齐与集体旋转

Cavity optomechanics in ultrastrong light matter coupling regime: Self-alignment and collective rotation mediated by Casimir torque

该研究理论上探讨了光学腔内量子二聚体系综在超强耦合下的行为，预测了由腔光子交换角动量引起的二聚体自对齐，以及手性腔真空态角动量转移导致的集体同步旋转两种新效应。

在受限几何结构中操控偶极相互作用与协同效应

Manipulating the Dipolar Interactions and Cooperative Effects in Confined Geometries

本文研究受限纳米结构中热蒸气的原子间相互作用，发现其偏离连续电动力学模型，并证明通过控制单原子饱和、多原子相互作用及原子云几何形状，可操控原子系综的光学非线性，为量子应用提供可扩展的混合平台。

Collective dynamics of inhomogeneously broadened emitters coupled to an optical cavity with narrow linewidth

We study collective effects in an inhomogeneously broadened ensemble of two-level emitters coupled to an optical cavity with narrow linewidth. Using second order mean field theory we find that the emitters within a few times the cavity linewidth exhibit synchronous behaviour and undergo collective Rabi oscillations. Under proper conditions, the synchronized oscillations give rise to a modulated intracavity field which can excite emitters detuned by many linewidths from the cavity resonance. To study the synchronization in further detail, we simplify the model and consider two ensembles and stu…

强相干场驱动下饱和态冷原子集体的非线性光学特性

Optical nonlinearity of cold atomic ensemble driven by strong coherent field in a saturation regime

研究强相干场驱动下冷原子集体的非线性光学特性，揭示其参数部分可通过调控相干泵浦和样品密度增强，指出量子通信中利用纠缠光子的局限性。

Preservation of quantum correlations in femtosecond light pulse train within atomic ensemble

In this paper, we examined a possibility of preservation of a substantially multimode radiation in a single cell of quantum memory. As a light source we considered a synchronously pumped optical parametric oscillator (SPOPO). As it was shown in [1-4], SPOPO radiation has a large number of the correlated modes making it attractive for the purposes of the quantum communication and computing. We showed that these correlations can be mapped on the longitudinal spin waves of the memory cell and be restored later in the readout light. The efficiencies of the writing and readout depend on the mode st…

Probing and Manipulating Fermionic and Bosonic Quantum Gases with Quantum Light

We study the atom-light interaction in the fully quantum regime, with focus on off-resonant light scattering into a cavity from ultracold atoms trapped in an optical lattice. The detection of photons allows the quantum nondemolition (QND) measurement of quantum correlations of the atomic ensemble, distinguishing between different quantum states. We analyse the entanglement between light and matter and show how it can be exploited for realising multimode macroscopic quantum superpositions such as Schrödinger cat states, for both bosons and fermions. We provide examples utilising different measu…

Coherent and Dynamic Beam Splitting based on Light Storage in Cold Atoms

We demonstrate a coherent and dynamic beam splitter based on light storage in cold atoms. An input weak laser pulse is first stored in a cold atom ensemble via electromagnetically-induced transparency (EIT). A set of counter-propagating control fields, applied at a later time, retrieves the stored pulse into two output spatial modes. The high visibility interference between the two output pulses clearly demonstrates that the beam splitting process is coherent. Furthermore, by manipulating the control lasers, it is possible to dynamically control the storage time, the power splitting ratio, the…

捕获、操控与探测超冷原子：量子技术教程

Trapping, manipulating and probing ultracold atoms: a quantum technologies tutorial

本教程综述超冷原子的捕获、操控与探测关键技术，涵盖激光冷却、光镊、干涉测量及多种成像方法，旨在为初学者提供实验工具包的全面概览。

Manipulating Rydberg atoms close to surfaces at cryogenic temperatures

Helium atoms in Rydberg states have been manipulated coherently with microwave radiation pulses near a gold surface and near a superconducting NbTiN surface at a temperature of $3 \text{K}$. The experiments were carried out with a skimmed supersonic beam of metastable $(1\text{s})^1(2\text{s})^1\, {}^1\text{S}_0$ helium atoms excited with laser radiation to $n\text{p}$ Rydberg levels with principal quantum number $n$ between $30$ and $40$. The separation between the cold surface and the center of the collimated beam is adjustable down to $250 μ\text{m}$. Short-lived $n\text{p}$ Rydberg levels …

Modulation stabilization of Bloch oscillations of two-component Bose-Einstein condensates in optical lattices

We study the Bloch oscillations (BOs) of two-component Bose-Einstein condensates (BECs) trapped in spin-dependent optical lattices. Based on the derived equations of motion of the wave packet in the basis of localized wave functions of the lattice sites, the damping effect induced by the intercomponent and intracomponent interactions to the BOs is explored analytically and numerically. We also show that such damping of the BOs can be suppressed entirely if all the atom-atom interactions are modulated synchronously and harmonically in time with suitable frequency via the Feshbach resonance. Whe…

A tweezer clock with half-minute atomic coherence at optical frequencies and high relative stability

The preparation of large, low-entropy, highly coherent ensembles of identical quantum systems is foundational for many studies in quantum metrology, simulation, and information. Here, we realize these features by leveraging the favorable properties of tweezer-trapped alkaline-earth atoms while introducing a new, hybrid approach to tailoring optical potentials that balances scalability, high-fidelity state preparation, site-resolved readout, and preservation of atomic coherence. With this approach, we achieve trapping and optical clock excited-state lifetimes exceeding $ 40 $ seconds in ensembl…

在光学晶格中制备分数量子霍尔态的最优控制

Optimal control for preparing fractional quantum Hall states in optical lattices

本文提出利用最优控制方法加速光学晶格中Laughlin型分数量子霍尔态的制备，通过优化极少数控制参数，在现实时间内实现更大规模FQH态，并验证了方案对误差和无序性的鲁棒性。