Interplay of creation, propagation, and relaxation of an excitation in a dimer

Nonclassical statistics of intracavity coupled $χ^{(2)}$ waveguides: the quantum optical dimer

A model is proposed where two $χ^{(2)}$ nonlinear waveguides are contained in a cavity suited for second-harmonic generation. The evanescent wave coupling between the waveguides is considered as weak, and the interplay between this coupling and the nonlinear interaction within the waveguides gives rise to quantum violations of the classical limit. These violations are particularly strong when two instabilities are competing, where twin-beam behavior is found as almost complete noise suppression in the difference of the fundamental intensities. Moreover, close to bistable transitions perfect tw…

远距离产生过程之间的量子干涉

Quantum interference between distant creation processes

本研究提出生成宏观量子系统的新方法，通过产生相距最远70米的相干叠加态光子对，验证量子系统产生过程可跨宏观距离，为量子基础实验及分布式特性高精度测量提供新可能。

Environmental design principles for efficient excitation energy transfer in dimer and trimer pigment-protein molecular aggregates and the relation to non-Markovianity

In this study, we explore optimal environments for efficient EET between end sites in a number of dimer and trimer model pigment-protein molecular aggregates when the EET dynamics is modeled by the HEOM-method. For these optimal environmental parameters, we further quantify the non-Markovianity by the BLP-measure to elucidate its possible connection to efficient EET. We also quantify coherence in the pigment systems by means of the measure l1-norm of coherence to analyze its interplay with environmental effects when EET efficiency is maximal. Our aim is to investigate possible environmental de…

Particle pair creation by inflation of quantum vacuum fluctuations in an ion trap

The creation of matter and structure in our universe is currently described by an intricate interplay of quantum field theory and general relativity. Signatures of this process during an early inflationary period can be observed, while direct tests remain out of reach. Here, we study an experimental analog of the process based on trapped atomic ions. We create pairs of phonons by tearing apart quantum vacuum fluctuations. Thereby, we prepare ions in an entangled state of motion. Controlling timescales and the coupling to environments should permit optimizing efficiencies while keeping the effe…

Quantum Classical Correspondence for a non-Hermitian Bose-Hubbard Dimer

We investigate the many-particle and mean-field correspondence for a non-Hermitian N-particle Bose-Hubbard dimer where a complex onsite energy describes an effective decay from one of the modes. Recently a generalized mean-field approximation for this non-Hermitian many-particle system yielding an alternative complex nonlinear Schrödinger equation was introduced. Here we give details of this mean-field approximation and show that the resulting dynamics can be expressed in a generalized canonical form that includes a metric gradient flow. The interplay of nonlinearity and non-Hermiticity introd…

Creation and detection of photonic molecules in Rydberg gases

We consider the propagation of photons in a gas of Rydberg atoms under conditions of electromagnetically induced transparency, where they form strongly interacting massive particles, termed Rydberg polaritons. Depending on the strength of the van der Waals-type interactions of the atoms either bunching or anti-bunching of photons can be observed when driving the atoms off-resonantly. The bunching is associated with the formation of bound states. We employ a Green's function approach and numerical wave-function simulations to analyze the conditions for the creation and the dynamics of these pho…

State-resolved infrared spectrum of the protonated water dimer: Revisiting the characteristic proton transfer doublet peak

The infrared (IR) spectra of protonated water clusters encode precise information on the dynamics and structure of the hydrated proton. However, the strong anharmonic coupling and quantum effects of these elusive species remain puzzling up to the present day. Here, we report unequivocal evidence that the interplay between the proton transfer and the water wagging motions in the protonated water dimer (Zundel ion) giving rise to the characteristic doublet peak is both more complex and more sensitive to subtle energetic changes than previously thought. In particular, hitherto overlooked low-inte…

Negative Thermal Hall Conductance in Two-Dimer Shastry-Sutherland Model with π-flux Dirac Triplon

We introduce an effective 2-dimer tight-binding model for the family of Shastry-Sutherland models with geometrically tunable triplon excitations. The Rashba pseudospin-orbit coupling induced by the tilted external magnetic field leads to elementary excitations having nontrivial topological properties with π-Berry flux. The interplay between the in-plane and out-of-plane magnetic field thus allows us to effectively engineer the band structure in this bosonic system. In particular, the in-plane magnetic field gives rise to Berry curvature hotspot near the bottom of the triplon band, and at the s…

Resonant Raman scattering of single molecules under strong cavity coupling and ultrastrong optomechanical coupling in plasmonic resonators: phonon-dressed polaritons

Plasmonic dimer cavities can induce extreme electric-field hot spots that allow one to access ultrastrong coupling regimes using Raman-type spectroscopy on single vibrating molecules. Using a generalized master equation, we study resonant Raman scattering in the strong coupling regime of cavity-QED, when also in the vibrational ultrastrong coupling regime, leading to "phonon-dressed polaritons". The master equation rigorously includes spectral baths for the cavity and vibrational degrees of freedom, as well as a pure dephasing bath for the resonant two-level system, which play a significant ro…

Magnon boundary states tailored by longitudinal spin-spin interactions and topology

Since longitudinal spin-spin interaction is ubiquitous in magnetic materials, it is very interesting to explore the interplay between topology and longitudinal spin-spin interaction. Here, we examine the role of longitudinal spin-spin interaction on topological magnon excitations. Remarkably, even for single-magnon excitations, we discover topological edge states and defect edge states of magnon excitations in a dimerized Heisenberg XXZ chain and their topological properties can be distinguished via adiabatic quantum transport. We uncover topological phase transitions induced by longitudinal s…

多能级波导QED中的多聚体态

Multimer states in multilevel waveguide QED

该研究针对耦合波导的多能级原子阵列中的多激发准稳态，提出基于亚辐射二聚体基的解析方法，发现原子势非简谐性驱动的多聚化效应及半填充下的周期高亚辐射直积态。

几何碎裂与立方二元模型中的异常热化

Geometric fragmentation and anomalous thermalization in cubic dimer model

研究立方二元模型中几何碎裂与异常热化现象，通过分析与数值方法揭示大缠绕区的无热态，发现电场方向的动态通量极化导致二维平面束缚激发，与垂直方向的高斯定律约束相互作用产生新守恒量，导致系统几何碎裂。

Ultracold $^{88}\rm{Sr}_2$ molecules in the absolute ground state

We report efficient all-optical creation of an ultracold gas of alkaline-earth-metal dimers, $^{88}\rm{Sr}_2$, in their absolute ground state. Starting with weakly bound singlet molecules formed by narrow-line photoassociation in an optical lattice, followed by stimulated Raman adiabatic passage (STIRAP) via a singlet-dominant channel in the $(1)0_u^+$ excited potential, we prepare pure samples of more than 5500 molecules in $X^1Σ_g^+(v=0,J=0)$. We observe two-body collisional loss rates close to the universal limit for both the least bound and most bound vibrational states in $X^1Σ_g^+$. We d…