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Understanding the nature of mean-field semiclassical light-matter dynamics: An investigation of energy transfer, electron-electron correlations, external driving, and long-time detailed balance
摘要： Semiclassical electrodynamics (with quantum matter plus classical electrodynamics fields) is an appealing approach for studying light-matter interactions, especially for realistic molecular systems. However, there is no unique semiclassical scheme. On the one hand, intermolecular interactions can be described instantaneously by static two-body interactions connecting two different molecules, while a classical transverse E field acts as a spectator at short distance; we will call this Hamiltonian no. I. On the other hand, intermolecular interactions can also be described as effects that are mediated exclusively through a classical one-body E field without any quantum effects at all (assuming we ignore electronic exchange); we will call this Hamiltonian no. II. Moreover, one can also mix these two different Hamiltonians into a third, hybrid Hamiltonian, which preserves quantum electron-electron correlations for lower excitations but describes higher excitations in a mean-field way. To investigate which semiclassical scheme is most reliable for practical use, here we study the real-time dynamics of a minimalistic many-site model—a pair of identical two-level systems (TLSs)—undergoing either resonance energy transfer (RET) or collectively driven dynamics. While both approaches (no. 1 and no. 2) perform reasonably well when there is no strong external excitation, we find that no single approach is perfect for all conditions (and all methods fail when a strong external field is applied). Each method has its own distinct problems: Hamiltonian no. I performs best for RET but behaves in a complicated manner for driven dynamics; Hamiltonian no. II is always stable, but obviously fails for RET at short distances. One key finding is that, for externally driven dynamics, a full configuration-interaction description of Hamiltonian no. I strongly overestimates the long-time electronic energy, highlighting the not obvious fact that, if one plans to merge quantum molecules with classical light, a full, exact treatment of electron-electron correlations can actually lead to worse results than a simple mean-field electronic structure treatment. Future work will need to investigate (i) how these algorithms behave in the context of more than a pair of TLSs and (ii) whether or not these algorithms can be improved in general by including crucial aspects of spontaneous emission.
关键词： resonance energy transfer,semiclassical electrodynamics,mean-field dynamics,light-matter interactions,electron-electron correlations
更新于2025-09-12 10:27:22
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Mesoscopic two-mode entangled and steerable states of 40?000 atoms in a Bose-Einstein-condensate interferometer
摘要： Using criteria based on superselection rules that apply to massive bosons but not to photons, we analyze the quantum correlations between the two condensate modes of a Bose-Einstein condensate interferometer [described in Egorov et al., Phys. Rev. A 84, 021605 (2011)]. We show that the observation of interference fringes can only be explained by Einstein-Podolsky-Rosen steering correlations between the two modes. Moreover, the size of the two-mode correlation linked to the fringe visibility will place a lower bound on the mean number of atoms of the (pure) two-mode steerable state. In order to determine the two-mode correlations, we develop a multimode theory describing the dynamics of the condensate atoms and the thermal fraction through the interferometer sequence, in agreement with the experimentally measured fringe visibility. We thus present experimental evidence for two-mode entangled states genuinely involving 40 000 87Rb atoms, and for two-way steerability between two groups of 20 000 indistinguishable atoms.
关键词： Bose-Einstein condensate,EPR steering,quantum correlations,superselection rules,interferometer
更新于2025-09-12 10:27:22
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[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Controllable Photon-Pair Spectral Correlations
摘要： Photon-pair states, whether spectrally correlated or separable, can all be very useful in quantum technology applications. For example, the former are used for improving the security of quantum key distribution, whilst the latter are the backbone in heralded single photon sources. It has been shown that the amount of spectral correlations is well-described by the shape of the Joint Spectral Amplitude function (JSA), which mostly depends on the relative group velocity relation between the pump, signal and idler photons within the source medium [1]. Here, we report on a photon-pair source whose states can be controlled from separable to spectrally entangled. The source is based on four-wave mixing nonlinear effect within a gas-filled hollow-core photonic crystal fiber (HCPCF). It combines three important properties: (1) Raman-free generation thanks to the use of a noble gas and to a minute overlap with silica within the hollow-core [2]; (2) strong efficiency nonlinear medium and (3) a high versatility in the phase-matching conditions thanks to the fiber microstructuration and gas pressure tunability. The inhibited-coupling HCPCF (see Fig.1a) filled with xenon, was designed to operate at wavelengths that are convenient for heralded single photon sources; the idler lies in the telecom wavelength range (~ 1545 nm), while the signal wavelength is in the range of atomic transitions and Silicon single photon detectors (~ 778 nm). More importantly, we show how the multiband dispersion profile (see Fig. 1b) of such medium allows to tailor phase- and group velocity relations and possibly at any given wavelength from the UV to infrared [3]. We demonstrate experimentally an active control over the generated photon spectral-correlation that allows spectrally entangled and factorable states to be obtained within the same device (examples in Fig. 1c). More specifically, a gallery of different JSI, including exotic shape, is measured by tuning various parameters: gas pressure, pump spectral FWHM, spectral chirp and pump spectral envelope. Such a versatile photon-pair source can target both applications requiring factorable (heralded single photon) and correlated states (spectral entanglement) and paves the way to spectro-temporal mode encoding [4]. Furthermore, the photon-pair state is generated over an unprecedented tunable frequency-range that span well over tens of THz. We will present complete theoretical and experimental results demonstrating the full capacity of this platform to generate photon pair with controllable spectral properties.
关键词： photon-pair states,hollow-core photonic crystal fiber,spectral correlations,quantum technology,spectral entanglement,four-wave mixing
更新于2025-09-11 14:15:04
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Coulomb drag in strongly coupled quantum wells: Temperature dependence of the many-body correlations
摘要： We investigate the effect of the temperature dependence of many-body correlations on hole–hole Coulomb drag in strongly coupled GaAs/GaAlAs double quantum wells. For arbitrary temperatures, we obtained the correlations using the classical-map hypernetted-chain approach. We compare the temperature dependence of the resulting drag resistivities qDeTT at different densities with qDeTT calculated assuming correlations ?xed at zero temperature. Comparing the results with those when correlations are completely neglected, we con?rm that correlations signi?cantly increase the drag. We ?nd that the drag becomes sensitive to the temperature dependence of T (cid:2) 2TF, twice the Fermi temperature. Our results show excellent agreement with available experimental data.
关键词： Coulomb drag,many-body correlations,temperature dependence,quantum wells
更新于2025-09-11 14:15:04
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Path-integral Monte Carlo study of electronic states in quantum dots in an external magnetic field
摘要： We explore the correlated electron states in harmonically confined few-electron quantum dots in an external magnetic field by the path-integral Monte Carlo method for a wide range of the field and the Coulomb interaction strength. Using the phase structure of a preceding unrestricted Hartree-Fock calculation for phase fixing, we find a rich variety of correlated states, often completely different from the prediction of mean-field theory. These are finite temperature results, but sometimes the correlations saturate with decreasing temperature, providing insight into the ground-state properties.
关键词： magnetic field,electron correlations,Hartree-Fock,quantum dots,path-integral Monte Carlo
更新于2025-09-11 14:15:04
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The model of the fullerene C60 and its ions C60+, C60??pseudopotentials for molecular dynamics purposes
摘要： The model pseudopotentials of C?60, C60 and C+60 have been constructed on the base of the total electrostatic potentials obtained as a result of ab initio-based calculations. The radial distance dependence of the pseudopotential is obtained by averaging with respect to the spherical angles of the total electrostatic potential. The role of the electronic correlations is investigated by comparison results of using of the di?erent exchange-correlation functional within the density functional theory. All pseudopotentials are ?tted by the ?ne approximation functions and can be applied for molecular dynamics tasks.
关键词： molecular dynamics,electronic correlations,pseudopotentials,fullerene C60,ab initio calculations
更新于2025-09-10 09:29:36
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Dynamics of surface evolution of rutile TiO <sub/>2</sub> (110) after ion irradiation
摘要： The dynamics of TiO2 surfaces evolving under 60 keV Ar+ ions have been explored here. Dynamic scaling ansatz, height–height correlation (HHC) model and power spectral density (PSD) model have been applied to investigate the growth mechanisms. The surfaces are growing under non-equilibrium growth processes and three separate domains of evolution have been noticed. Early time growth of the surfaces can be characterized by roughness exponent, α ～ 0.72–0.74, and growth exponent, β ～ 0.3. Dominance of diffusion is also noticed with Edward Wilkinson (EW) growth scaling. In the next time regime, non-local instabilities get incorporated, due to sputter-induced nanostructuring of the surfaces, resulting in a rapid surface roughening with a high value of β. The surface roughness saturates in late time regime.
关键词： height–height correlations,TiO2,power spectral density,AFM
更新于2025-09-10 09:29:36
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Hong–Ou–Mandel-like two-droplet correlations
摘要： We present a numerical study of two-droplet pair correlations for in-phase droplets walking on a vibrating bath. Two such walkers are launched toward a common point of intersection. As they approach, their carrier waves may overlap and the droplets have a non-zero probability of forming a two-droplet bound state. The likelihood of such pairing is quanti?ed by measuring the probability of ?nding the droplets in a bound state at late times. Three generic types of two-droplet correlations are observed: promenading, orbiting, and chasing pair of walkers. For certain parameters, the droplets may become correlated for certain initial path differences and remain uncorrelated for others, while in other cases, the droplets may never produce droplet pairs. These observations pave the way for further studies of strongly correlated many-droplet behaviors in the hydrodynamical quantum analogs of bouncing and walking droplets.
关键词： walking droplets,hydrodynamical quantum analogs,two-droplet correlations,vibrating bath
更新于2025-09-10 09:29:36
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Positive and negative correlations in computational ghost imaging for a grayscale object
摘要： Our previous work has studied the positive-negative correlations in computational ghost imaging for a binary object. In this work, we focus on the computational ghost imaging system for a grayscale object. We studied the second-order correlation function of this system, and gave the criterion of the positive and negative correlations. Furthermore, this criterion was verified by using numerical simulations.
关键词： computational ghost imaging,grayscale object,second-order correlation function,positive-negative correlations
更新于2025-09-10 09:29:36
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Electronic wavefunctions probed by all-optical attosecond interferometry
摘要： In photoelectron spectroscopy, the ionized electron wavefunction carries information about the structure of the bound orbital and the ionic potential as well as about the photoionization dynamics. However, retrieving the quantum phase information has been a long-standing challenge. Here, we transfer the electron phase retrieval problem into an optical one by measuring the time-reversed process of photoionization—photo-recombination—in attosecond pulse generation. We demonstrate all-optical interferometry of two independent phase-locked attosecond light sources. This measurement enables us to directly determine the phase shift associated with electron scattering in simple quantum systems such as helium and neon, over a large energy range. Moreover, the strong-field nature of attosecond pulse generation resolves the dipole phase around the Cooper minimum in argon through a single scattering angle. This method may enable the probing of complex orbital phases in molecular systems as well as electron correlations through resonances subject to strong laser fields.
关键词： all-optical interferometry,electron correlations,photoelectron spectroscopy,Cooper minimum,molecular systems,electron scattering,attosecond pulse generation,quantum phase information
更新于2025-09-10 09:29:36