We propose a method to realize enantiodiscrimination of chiral molecules based on quantum correlation function in a driven cavity-molecule system, where the chiral molecule is coupled with a quantized cavity field and two classical light fields to form a cyclic three-level model. According to the inherent properties of electric-dipole transition moments of chiral molecules, there is a $π$-phase difference in the overall phase of the cyclic three-level model for the left- and right-handed chiral molecules. Thus, the correlation function depends on this overall phase and is chirality-dependent. The analytical and numerical results indicate that the left- and right-handed chiral molecules can be discriminated by detecting quantum correlation function. Our work opens up a promising route to discriminate molecular chirality, which is an extremely important task in pharmacology and biochemistry.
We study the enantio-specific state transfer in a four-level model for symmetric-top chiral molecules. Such a model is formed by coupling the electric-dipole transitions among four appropriate working states with three electromagnetic fields. It includes two cyclic three-level substructures, where the overall phases differ by $π$ with enantiomers and reflect the chirality dependence of the molecule. Based on this four-level model, two dynamic ways are proposed to achieve the approximately perfect enantio-specific state transfer for symmetric-top chiral molecules.
The van der Waals dispersion interaction between two chiral molecules in the presence of arbirary magnetoelectric media is derived using perturbation theory. To be general, the molecular polarisabilities are assumed to be of electric, paramagnetic and diamagnetic natures and the material environment is considered to possess a chiral electromagnetic response. The derived formulas of electric-chiral, paramagnetic-chiral, diamagnetic-chiral and chiral-chiral interaction potentials when added to the previously obtained contributions in literature, form a complete set of dispersion interaction form…
The Stern-Gerlach effect is well-known as spin-dependent splitting of a beam of atoms with magnetic moments by a magnetic-field gradient. Here, we show that an induced gauge potential may lead to a similar effect for chiral molecules. In the presence of three inhomogeneous light fields, the center-of-mass of a three-level chiral molecule is subject to an optically induced gauge potential, and the internal dynamics of the molecules can be described as an adiabatic evolution in the reduced pseudo-spin subspace of the two lowest energy levels. We demonstrate numerically that such an induced gauge…
Resonance energy transfer between chiral molecules can be used to discriminate between different enantiomers. The transfer rate between chiral molecules consists of a non-discriminatory and discriminatory parts. We derive these two rate contributions in the framework of macroscopic quantum electrodynamics. We show that their ratio is usually larger in the retarded regime or far-zone of large separation distances and that the degree of discrimination can be modified when considering a surrounding medium. We highlight the importance of local field effects onto the degree of discrimination and pr…
We study quantum systems with broken symmetry that can be modelled as cyclic three-level atoms with coexisting one- and two-photon transitions. They can be selectively optically excited to any state. As an example, we show that left- and right-handed chiral molecules starting in the same initial states can evolve into different final states by a purely dynamic transfer process. That means, left- and right-handed molecules can be distinguished purely dynamically.
We develop a dynamical approach to study the Casimir-Polder force between a initially bare molecule and a magnetodielectric body at finite temperature. Switching on the interaction between the molecule and the field at a particular time, we study the resulting temporal evolution of the Casimir-Polder interaction. The dynamical self-dressing of the molecule and its population-induced dynamics are accounted for and discussed. In particular, we find that the Casimir-Polder force between a chiral molecule and a perfect mirror oscillates in time with a frequency related to the molecular transition …
Molecular matter-wave interferometry enables novel strategies for manipulating the internal mechanical motion of complex molecules. Here, we show how chiral molecules can be prepared in a quantum superposition of two enantiomers by far-field matter-wave diffraction and how the resulting tunnelling dynamics can be observed. We determine the impact of ro-vibrational phase averaging and propose a setup for sensing enantiomer-dependent forces, parity-violating weak interactions, and environment-induced superselection of handedness, as suggested to resolve Hund's paradox. Using ab-initio tunnelling…
Single-loop cyclic three-level ($Δ$-type) configuration of chiral molecules was used for enantio-separation in many theoretical works. Considering the effect of molecular rotation, this simple single-loop configuration is generally replaced by a complicated multiple-loop configuration containing multiple degenerate magnetic sub-levels and the ability of the enantio-separation methods is suppressed. For chiral asymmetric top molecules, we propose a scheme to construct a real single-loop $Δ$-type configuration with no connections to other states by applying three microwave fields with appropriat…
Chiral molecules with broken parity symmetries can be modeled as quantum systems with cyclic-transition structures. By using these novel properties, we design two-step laser pulses to distinguish left- and right-handed molecules from the enantiomers. After the applied pulse drivings, one kind chiral molecules are trapped in coherent population trapping state, while the other ones are pumped to the highest states for ionizations. Then, different chiral molecules can be separated.
A highly-efficient method for optical detection and separation of left- and right-handed chiral molecules is presented. The method utilizes a closed-loop three-state system in which the population dynamics depends on the phases of the three couplings. Due to the different signs of the coupling between two of the states for the opposite chiralities and the phase sensitivity of the scheme, the population dynamics is chirality-dependent. By using concepts from the `shortcuts to adiabaticity' approach, one can achieve 100\% contrast in state population transfer between the two enantiomers, which c…
We propose to discriminate chiral molecules by combining one- and two-photon processes in a closed-loop configuration. The one-photon-coupling intrinsic π-phase difference between two enantiomers leads to their different superposition states, which is then followed by a two-photon process through three-mode parallel paths (3MPPs), enabling the discrimination of enantiomers by inducing their entirely-different population distributions. The 3MPPs are constructed by "chosen paths", a method of shortcuts to adiabaticity (STA), exhibiting a fast two-photon process. As an example, we propose to perf…
We prove complete controllability for rotational states of an asymmetric top molecule belonging to degenerate values of the orientational quantum number M. Based on this insight, we construct a pulse sequence that energetically separates population initially distributed over degenerate M-states, as a precursor for orientational purification. Introducing the concept of enantio-selective controllability, we determine the conditions for complete enantiomer-specific population transfer in chiral molecules and construct pulse sequences realizing this transfer for population initially distributed ov…
In the mean-field theory, the stabilization of polar chiral molecules is understood as a quantum phase transition where the mean-field ground state of molecules changes from the achiral eigenstate of the molecular Hamiltonian to one of the degenerated chiral states as the increase of the intermolecular interaction. Starting from the many-body Hamiltonian of the molecular gases with electric dipole-dipole interactions, we give the static non-linear Schrödinger equations without free parameters to explore the achiral-chiral transitions of polar chiral molecules. We find that the polar chiral mol…
In response to arXiv:1506.07423v1 we discuss the authors work, and our own, on proposed schemes aiming to achieve a discriminatory optical force for chiral molecules.
The decoherence of a two-state tunneling molecule, such as a chiral molecule or ammonia, due to collisions with a buffer gas is analyzed in terms of a succession of quantum states of the molecule satisfying the conditions for a consistent family of histories. With $\hbar ω$ the separation in energy of the levels in the isolated molecule and $γ$ a decoherence rate proportional to the rate of collisions, we find for $γ\gg ω$ (strong decoherence) a consistent family in which the molecule flips randomly back and forth between the left- and right-handed chiral states in a stationary Markov process.…
State-selective enantiomeric excess is realized using microwave-driven coherent population transfer. The method selectively promotes either R or S molecules to a higher rotational state by phase-controlled microwave pulses that drive electric-dipole allowed rotational transitions. We demonstrate the enantiomer-specific state transfer method using enantiopure samples of 1,2-propanediol. This method of state-specific enantiomeric enrichment can be applied to a large class of asymmetric, chiral molecules that can be vaporized and cooled to the point where rotationally resolved spectroscopy is pos…
Enantiodetection of chiral molecules is important to pharmaceutical drug production, chemical reaction control, and biological function designs. Traditional optical methods of enantiodetection rely on the weak magnetic-dipole or electric-quadrupole interactions, and in turn suffer from the weak signal and low sensitivity. We propose a new optical enantiodetection method to determine the enantiomeric excess via two-dimensional (2D) spectroscopy of the chiral mixture driven by three electromagnetic fields. The quantities of left- and right- handed chiral molecules are reflected by the intensitie…
We propose an enantio-detection method of chiral molecules in a cavity with external drive. The chiral molecules are coupled with a quantized cavity field and two classical light fields to form the cyclic three-level systems. The chirality-dependent cavity-assisted three-photon process in the three-level systems leads to the generation of intracavity photons. Simultaneously, the drive field also results in the chirality-independent process of the generation of intracavity photons. Based on the interference between the intracavity photons generated from these two processes, one can detect the e…
We examine the dynamics of chiral states of chiral molecules with high tunneling rates in dilute and condensed phases in the context of time-dependent perturbation theory. The chiral molecule is effectively described by an asymmetric double-well potential, whose asymmetry is a measure of chiral interactions. The dilute and condensed phases are conjointly described by a collection of harmonic oscillators but respectively with temperature-dependent sub-ohmic and temperature-independent ohmic spectral densities. We examine our method quantitatively by applying the dynamics to isotopic ammonia mol…
The superposition of chiral states of chiral molecules, as delocalized quantum states of a many-particle system, can be used for the experimental investigations of decoherence theory. In this regard, a great challenge is the precise quantification of the robustness of these superpositions against environmental effects. The methods so far proposed need the detailed specification of the internal states of the molecule, usually requiring heavy numerical calculations. Here, by using the linearized quantum Boltzmann equation and by borrowing ideas employed for analyzing other quantum systems, we pr…
The algebraic structure of central molecular chirality can be achieved starting from the geometrical representation of bonds of tetrahedral molecules, as complex numbers in polar form, and the empirical Fischer projections used in organic chemistry. A general orthogonal O(4) algebra is derived from which we obtain a chirality index related to the classification of a molecule as achiral, diastereoisomer or enantiomer. Consequently, the chiral features of tetrahedral chains can be predicted by means of a molecular Aufbau. Moreover, a consistent Schroedinger equation is developed, whose solutions…
We explore the spatial enantioseparation of gaseous chiral molecules for the cyclic three-level systems coupled with three electromagnetic fields. Due to molecular rotations, the specific requirements of the polarization directions of the three electromagnetic fields lead to the space-dependent part of the overall phase of the coupling strengths. Thus, the overall phase of the coupling strengths, which differs with $π$ for the enantiomers in the cyclic three-level model of chiral molecules, varies intensely in the length scale of the typical wavelength of the applied electromagnetic fields. Un…
We identify the dominant collisional decoherence mechanism which serves to stabilize and super-select the configuration states of chiral molecules. A high-energy description of this effect is compared to the results of the exact molecular scattering problem, obtained by solving the coupled-channel equations. It allows to predict the experimental conditions for observing the collisional suppression of the tunneling dynamics between the left-handed and the right-handed configuration of D2S2 molecules.
Three-wave mixing spectroscopy of chiral molecules, which exist in left-handed and right-handed conformations, allows for enantio-selective population transfer despite random orientation of the molecules. This is based on constructive interference of the three-photon pathways for one enantiomer and destructive one for the other. We prove here that three mutually orthogonal polarization directions are required to this end. Two different dynamical regimes exist to realize enantio-selective population transfer, and we show that they correspond to different phase conditions in the three-wave mixin…
Parity violation in a chiral, four-atom molecule is discussed. Given the geometrical positions of the four atoms, we calculate the anapole moment of it. This problem was first discussed by Khriplovich and Pospelov. We give a detailed derivation for it so that it can be more accessible to wider range of scientists. We correct errors in their results and generalize their initial state to |s_{1/2}\rangle and |p_{1/2}\rangle states. We also discuss realistic candidates of the chiral molecules to which this approach can be applied.
We reveal the existence of polarizing quantum phases for the enantiomers of cold, interacting chiral molecules in an optical helicity lattice by means of an extended Bose-Hubbard model. These recently proposed lattices have sites with alternating helicity which exert a discriminatory force on chiral molecules with different handedness. In our study of the phase diagram we find that a strong dipolar repulsion between molecules results in the separation of left and right enantiomers.
Bose-Einstein condensation of a sample of non-interacting chiral molecules leads to a non zero optical activity of the condensate and also to a subcritical temperature in the heat capacity. This is due to the internal structure of the molecule which, in our model, is considered as a simple two-state system, characterized by tunneling and parity violation. The predicted singular behavior found for the specific heat, below the condensation temperature, sheds some light on the existence of the so far elusive parity violation energy difference between enantiomers.
The radiation of optically active (chiral) molecule placed near chiral nanoparticle is investigated. The optimal conditions for engineering of radiation of optically active (chiral) molecules with the help of chiral nanoparticles are derived. It is shown that for this purpose, the substance of the chiral particle must have both ε_and μ_negative (double negative material (DNG)) or negative μ_and positive ε_(μ_negative material (MNG)). Our results pave the way to an effective engineering of radiation of "left" and "right" molecules and to creating pure optical devices for separation of drugs ena…
In the framework of the perturbation theory of the nonrelativistic quantum electrodynamics, a theory of spontaneous emission of a chiral molecule located near a chiral (bi-isotropic) spherical particle is developed. It is shown that the structure of photons in the presence of chiral spherical particles differs significantly from the structure of TE or TM photons. Exact analytical expressions for the spontaneous emission radiative decay rate of a chiral molecule with arbitrary electric and magnetic dipole moments of transition located near a chiral spherical particle with arbitrary parameters a…
In a classical description, a neutral, polarizable object acquires a kinetic momentum when exposed to crossed electric and magnetic fields. In the presence of only a magnetic field no such momentum exists classically, although it is symmetry-allowed for an object lacking mirror symmetry. We perform a full QED calculation to show that the quantum vacuum coupled to a chiral molecule provides a kinetic "Casimir" momentum directed along the magnetic field, proportional to its rotatory power and the fine structure constant.
The chiral component of the Casimir-Polder potential is derived within the framework of macroscopic quantum electrodynamics. It is shown to exist only if the particle and the medium are both chiral. Furthermore, the chiral component of the Casimir-Polder potential can be attractive or repulsive, depending on the chirality of the molecule and the medium. The theory is applied to a cavity geometry in the non-retarded limit with the intention of enantiomer separation. For a ground state molecule the chiral component is dominated by the electric component and thus no explicit separation will happe…
The physical origin of the so-called chirality-induced spin selectivity (CISS) effect has puzzled experimental and theoretical researchers over the past few years. Early experiments were interpreted in terms of unconventional spin-orbit interactions mediated by the helical geometry. However, more recent experimental studies have clearly revealed that electronic exchange interactions also play a key role in the magnetic response of chiral molecules in singlet states. In this investigation, we use spin-polarized closed shell density functional theory calculations to address the influence of exch…
Angular distribution of photoelectrons released by the ionization of randomly-oriented molecules with two laser fields of carrier frequencies $ω$ and $2ω$, which are linearly polarized in two mutually-orthogonal directions, is analyzed in the perturbation limit for the case of one- vs two-photon ionization process. In particular, we focus on the recently predicted [Ph.V. Demekhin {\it et al.}, Phys. Rev. Lett. \textbf{121}, 253201 (2018)] forward-backward asymmetry in the photoelectron emission, which is induced by the interference of two fields and depends on the external relative phase betwe…
Photoelectron circular dichroism results from one-photon ionization of chiral molecules by circularly polarized light and manifests itself in forward-backward asymmetry of electron emission in the direction orthogonal to the light polarization plane. What is the physical mechanism underlying asymmetric electron ejection? How "which way" information builds up in a chiral molecule and maps into forward-backward asymmetry? We introduce instances of bound chiral wave functions resulting from stationary superpositions of states in a hydrogen atom and use them to show that the chiral response in one…
Enantiodetection is an important and challenging task across natural science. Nowadays, some chiroptical methods of enantiodetection based on decoherence-free cyclic three-level models of chiral molecules can reach the ultimate limit of the enantioselectivities in the molecular responses. They are thus more efficient than traditional chiroptical methods. However, decoherence is inevitable and can severely reduce enantioselectivities in these advanced chiroptical methods, so they only work well in the weak decoherence region. Here, we propose an enantioselective switch on the radiation of dissi…
Photoelectron circular dichroism results from one-photon ionization of chiral molecules by circularly polarized light and manifests itself in forward-backward asymmetry of electron emission in the direction orthogonal to the light polarization plane. To expose the physical mechanism responsible for asymmetric electron ejection, we first establish a rigorous relation between the responses of unaligned and partially or perfectly aligned molecules. Next, we identify a propensity field, which is responsible for the chiral response in the electric-dipole approximation, i.e. a chiral response withou…
We predict a discriminatory interaction between a chiral molecule and an achiral molecule which is mediated by a chiral body. To achieve this, we generalize the van der Waals interaction potential between two ground-state molecules with electric, magnetic and chiral response to non-trivial environments. The force is evaluated using second-order perturbation theory with an effective Hamiltonian. Chiral media enhance or reduce the free interaction via many-body interactions, making it possible to measure the chiral contributions to the van der Waals force with current technology. The van der Waa…
We explore the interplay between tunneling process and chiral interactions in the discrimination of chiral states for an ensemble of molecules in a biological environment. Each molecule is described by an asymmetric double-well potential and the environment is modeled as a bath of harmonic oscillators. We carefully analyze different time-scales appearing in the resulting master equation at both weak- and strong-coupling limits. The corresponding results are accompanied by a set of coupled differential equations characterizing optical activity of the molecules. We show that, at the weak-couplin…
Collapse models provide a theoretical framework for understanding how classical world emerges from quantum mechanics. Their dynamics preserves (practically) quantum linearity for microscopic systems, while it becomes strongly nonlinear when moving towards macroscopic scale. The conventional approach to test collapse models is to create spatial superpositions of mesoscopic systems and then examine the loss of interference, while environmental noises are engineered carefully. Here we investigate a different approach: We study systems that naturally oscillate --creating quantum superpositions-- a…
We present a comprehensive study of enantioselective orientation of chiral molecules excited by a pair of delayed cross-polarized femtosecond laser pulses. We show that by optimizing the pulses' parameters, a significant (~ 10%) degree of enantioselective orientation can be achieved at zero and at five kelvin rotational temperatures. This study suggests a set of reasonable experimental conditions for inducing and measuring strong enantioselective orientation. The strong enantioselective orientation and the wide availability of the femtosecond laser systems required for the proposed experiments…
We propose an approach to sensitively probe the chirality of molecules by measuring their coherent optical absorption spectra. It is shown that quantum dynamics of the cyclic three-level chiral molecules driven by appropriately-designed external fields is total-phase dependent. This will result in chirality-dependent absorption spectra for the probe field. As a consequence, these absorption spectra can be utilized to identify molecular chirality and determinate enantiomer excess. The feasibility of the proposal with chiral molecules confined in hollow-core photonic crystal fiber (HC-PCF) is al…
Spin-current correlations in photoionization of chiral molecules
Max-Born-Institut（马克斯·伯恩研究所）；Humboldt University zu Berlin（柏林洪堡大学）；Technion - Israel Institute of Technology（以色列理工学院）；Imperial College London（伦敦帝国理工学院）；Freie Universität Berlin（柏林自由大学）；Technische Universität Berlin（柏林工业大学）
Parity violation (PV) effects in chiral molecules have so far never been experimentally observed. To take this challenge up, a consortium of physicists, chemists, theoreticians and spectroscopists has been established and aims at measuring PV energy differences between two enantiomers by using high-resolution laser spectroscopy. In this article, we present our common strategy to reach this goal, the progress accomplished in the diverse areas, and point out directions for future PV observations. The work of André Collet on bromochlorofluoromethane enantiomers, their synthesis and their chiral r…
Chiral-induced spin selectivity (CISS) is a phenomenon in which electron spins are polarized as they are transported through chiral molecules, and the spin polarization depends on the handedness of the chiral molecule. In this study, we show that spin selectivity can be realized in achiral materials by coupling electrons to a single mode of a chiral optical cavity. By investigating spin-dependent electron transport using the nonequilibrium Green's function approach, the spin polarization in a two-terminal setup is demonstrated to approach unity if the rate of dephasing is sufficiently small an…
