We investigate theoretically the non-Markovian dynamics of a degenerate V-type quantum emitter in the vicinity of a metallic nanosphere, a system that exhibits quantum interference in spontaneous emission due to the anisotropic Purcell effect. We calculate numerically the electromagnetic Green's tensor and employ the effective modes differential equation method for calculating the quantum dynamics of the emitter population, with respect to the resonance frequency and the initial state of the emitter, as well as its distance from the nanosphere. We find that the emitter population evolution varies between a gradually total decay and a partial decay combined with oscillatory population dynamics, depending strongly on the specific values of the above three parameters. Under strong coupling conditions, coherent population trapping can be observed in this system. We compare our exact results with results when the flat continuum approximation for the modified by the metallic nanosphere vacuum is applied. We conclude that the flat continuum approximation is an excellent approximation only when the spectral density of the system under study is characterized by non-overlapping plasmonic resonances.
Placing a quantum dot close to a metal nanowire leads to drastic changes in its radiative decay behavior because of evanescent couplings to surface plasmons. We show how two non-Markovian effects, band-edge and retardation, could be observed in such a system. Combined with a quantum dot p-i-n junction, these effects could be readout via current-noise measurements. We also discuss how these effects can occur in similar systems with restricted geometries, like phononic cavities and photonic crystal waveguides. This work links two previously separate topics: surface-plasmons and current-noise mea…
The radiative decay of quantum dot (QD) excitons into surface plasmons in a cylindrical nanowire is investigated theoretically. Maxwell's equations with appropriate boundary conditions are solved numerically to obtain the dispersion relations of surface plasmons. The radiative decay rate of QD excitons is found to be greatly enhanced at certain values of the exciton bandgap. Analogous to the decay of a two-level atom in the photonic crystal, we first point out that such an enhanced phenomenon allows one to examine the non-Markovian dynamics of the QD exciton. Besides, due to the one dimensiona…
We study two distinct multi-level atomic models in which one transition is coupled to a Markovian reservoir, while another linked transition is coupled to a non-Markovian reservoir. We show that by choosing appropriately the density of modes of the non-Markovian reservoir the spontaneous emission to the Markovian reservoir is greatly altered. The existence of `dark lines' in the spontaneous emission spectrum in the Markovian reservoir due to the coupling to specific density of modes of the non-Markovian reservoir is also predicted.
We demonstrate strong confinement of the optical field by depositing a micron sized metallic disk on a planar interferential mirror. Zero dimensional Tamm plasmon modes are evidenced both experimentally and theoretically, with a lateral confinement limited to the disk area and strong coupling to TE polarized fields. Single quantum dots deterministically coupled to these modes are shown to experience acceleration of their spontaneous emission when spectrally resonant with the mode. For quantum dots spectrally detuned from the confined Tamm Plasmon mode, an inhibition of spontaneous emission by …
The measurement-result-conditioned evolution of a system (e.g. an atom) with spontaneous emissions of photons is well described by the quantum trajectory (QT) theory. In this work we generalize the associated QT theory from infinitely wide bandwidth Markovian environment to the case of finite bandwidth non-Markovian environment. In particular, we generalize the treatment for arbitrary spectrum, which is not restricted by the specific Lorentzian case. We rigorously prove a general existence of a perfect scaling behavior jointly defined by the bandwidth of environment and the time interval betwe…
We analyze the non-Markovian dynamics of a quantum system subject to spontaneous collapse in space. After having proved, under suitable conditions, the separation of the center-of-mass and relative motions, we focus our analysis on the time evolution of the center of mass of an isolated system (free particle case). We compute the explicit expression of the Green's function, for a generic Gaussian noise, and analyze in detail the case of an exponential correlation function. We study the time evolution of average quantities, such as the mean position, momentum and energy. We eventually specializ…
In this work we present a large-deviation analysis for the counting statistics of atomic spontaneous emissions continuously detected in finite-bandwidth non-Markovian environment. We show that the statistics of the spontaneous emissions depends on the response time of the detector, which can result in big differences such as dynamical phase transition. This feature excludes the idea of regarding the spontaneous emissions as detection-free objective events. Possible experiment is briefly discussed in connection with the state-of-the-art optical cavity set-up.
A bound state between a quantum emitter (QE) and surface plasmon polaritons (SPPs) can be formed, where the QE is partially stabilized in its excited state. We put forward a general approach for calculating the energy level shift at a negative frequency $ω$, which is just the negative of the nonresonant part for the energy level shift at positive frequency $-ω$. We also propose an efficient formalism for obtaining the long-time value of the excited-state population without calculating the eigenfrequency of the bound state or performing a time evolution of the system, in which the probability a…
We demonstrate an approach, based on plasmonic apertures and gratings, to enhance the radiative decay rate of single NV centers in diamond, while simultaneously improving their collection efficiency. Our structures are based on metallic resonators formed by surrounding sub-wavelength diamond nanoposts with a silver film, which can enhance the spontaneous emission rate of an embedded NV center. However, the collection efficiency of emitted photons remains low due to losses to surface plasmons and reflections at the diamond-air interface. In this work, we mitigate photon losses into these channe…
We investigate the spontaneous emission of a two-level atom placed in the vicinities of a plasmonic cloak composed of a coated sphere. In the dipole approximation, we show that the spontaneous emission rate can be reduced to its vacuum value provided the atomic emission frequency lies within the plasmonic cloak frequency operation range. Considering the current status of plasmonic cloaking devices, this condition may be fulfilled for many atomic species so that we argue that atoms with a sufficiently strong transition can be used as quantum, local probes for the efficiency of plasmonic cloaks.
We introduce a method for calculating the dielectric function of nanostructures with an arbitrary band dispersion and Bloch wave functions. The linear response of a dissipative electronic system to an external electromagnetic field is calculated by a self-consistent-field approach within a Markovian master equation formalism (SCF-MMEF) coupled with full-wave electromagnetic equations. The SCF-MMEF accurately accounts for several concurrent scattering mechanisms. The method captures interband electron-hole-pair generation, as well as the interband and intraband electron scattering with phonons …
A non-perturbative theory of the spontaneous down conversion (SDC) of surface plasmon polaritons at a metal-dielectric interface is presented. It is shown that the process is resonantly enhanced for the characteristic power of excitation, typically of the order of tens of watts. At a stronger excitation the yield of SDC decreases rapidly. At a stronger excitation the yield of SDC decreases rapidly. The reason for this decrease is the high rate of the change of surface plasmon polaritons by the laser field, exceeding the rate of the zero-point fluctuations responsible for the SDC process. The o…
Spontaneous down conversion in metal-dielectric interface in case of oblique laser excitation is considered. In this case it is possible to generate pairs of polarization entangled surface plasmon polaritons with high efficiency if to use excitation angle corresponding to the Kretschmann configuration for generated plasmons. The efficiency can be additionally enlarged if to use properly nanostructured metallic film allowing one to directly excite surface plasmon polaritons and to fulfill phase matching condition of them with generated surface plasmon polaritons.
Manipulating the spontaneous emission of a fluorescent emitter can be achieved by placing the emitter in a nanostructured environment. A privileged spot is occupied by plasmonic structures that provide a strong confinement of the electromagnetic field, which results in an enhancement of the emitter-environment interaction. While plasmonic nanostructures have been widely exploited to control the emission properties of single photon emitters, performing the coupling between quantum emitters with plasmons poses a huge challenge. In this Letter we report on a first crucial step towards this goal b…
We study the collective radiative decay of a system of two two-level emitters coupled to a one-dimensional waveguide in a regime where their separation is comparable to the coherence length of a spontaneously emitted photon. The electromagnetic field propagating in the cavity-like geometry formed by the emitters exerts a retarded backaction on the system leading to strongly non-Markovian dynamics. The collective spontaneous emission rate of the emitters exhibits an enhancement or inhibition beyond the usual Dicke super- and sub-radiance due to a self-consistent coherent time-delayed feedback.
We experimentally demonstrate the control of the spontaneous emission rate and the radiation pattern of colloidal quantum dots deterministically positioned in a plasmonic patch antenna. The antenna consists of a thin gold microdisk 30 nm above a thick gold layer. The emitters are shown to radiate through the entire patch antenna in a highly directional and vertical radiation pattern. Strong acceleration of spontaneous emission is observed, depending of the antenna size. Considering the double dipole structure of the emitters, this corresponds to a Purcell factor up to 80 for dipoles perpendicu…
The ability to harness light-matter interactions at the few-photon level plays a pivotal role in quantum technologies. Single photons - the most elementary states of light - can be generated on-demand in atomic and solid state emitters. Two-photon states are also key quantum assets, but achieving them in individual emitters is challenging because their generation rate is much slower than competing one-photon processes. We demonstrate that atomically thin plasmonic nanostructures can harness two-photon spontaneous emission, resulting in giant far-field two-photon production, a wealth of resonan…
Detuned systems can spontaneously achieve a synchronous dynamics and display robust quantum correlations in different local and global dissipation regimes. Beyond the Markovian limit, information backflow from the environment becomes a crucial mechanism whose interplay with spontaneous synchronization is unknown. Considering a model of two coupled qubits, one of which interacts with a dissipative environment, we show that non-Markovianity is highly detrimental for the emergence of synchronization, for the latter can be delayed and hindered because of the presence of information backflow. The r…
For two qubits independently coupled to their respective structured reservoirs (Lorentzian spectrum), quantum beats for entanglement and discord are found which are the result of quantum interference between correlation oscillations induced by local non-Markovian environments. We also discuss the preservation of quantum correlations by the effective suppression of the spontaneous emission.
We theoretically investigate the spontaneous emission of a point--like dipolar emitter located near a two--dimensional (2D) plasmonic waveguide of arbitrary form. We invoke an explicite link with the density of modes of the waveguide describing the electromagnetic channels into which the emitter can couple. We obtain a closed form expression for the coupling to propagative plasmon, extending thus the Purcell factor to plasmonic configurations. Radiative and non-radiative contributions to the spontaneous emission are also discussed in details.
We introduce a photonic nanostructure made of two dimensional materials that can lead to non-Markovian dynamics in the spontaneous emission of a nearby quantum emitter. Specifically, we investigate the spontaneous emission dynamics of a two-level quantum emitter with picosecond free-space decay time, modelling J-aggregates, close to a MoS$_2$ nanodisk. Reversible population dynamics in the quantum emitter is obtained when the emitter's frequency matches the frequency of an exciton-polariton resonance created by the nanodisk. When such isolated resonances exist, decaying Rabi oscillations may o…
We study the dynamics of two two-level atoms embedded near to the interface of paired meta-material slabs, one of negative permeability and the other of negative permittivity. The interface behaves as a plasmonic waveguide composed of surface-plasmon polariton modes. It is found that significantly different dynamics occur for the resonant and an off-resonant couplings of the plasma field to the atoms. In the case of the resonant coupling, the plasma field does not appear as a dissipative reservoir to the atoms. We adopt the image method and show that the dynamics of the two atoms are completel…
We provide a critical analysis of some of the commonly used theoretical models to describe quantum plasmons. We summarize the standard approach based on a Fano diagonalization and we show explicit discrepancies in the obtained results by taking the limit of vanishing coupling between the electromagnetic field and the material medium. We then discuss the derivation of spontaneous emission in a plasmonic environment, which usually relies on a Green tensor and is based on an incomplete identity. The effect of the missing terms is calculated in a one-dimensional model.
Spontaneous parametric down-conversion (SPDC) is one of the most versatile nonlinear optical techniques for the generation of entangled and correlated single-photon pairs. However, it suffers from very poor efficiency leading to extremely weak photon generation rates. Here we propose a plasmonic metasurface design based on silver nanostripes combined with a bulk lithium niobate (LiNbO3) crystal to realize a new scalable, ultrathin, and efficient SPDC source. By coinciding fundamental and higher order resonances of the metasurface with the generated signal and idler frequencies, respectively, t…
We investigate a system consisting of a single, as well as two emitters strongly coupled to surface plasmon modes of a nano-wire using a Green function approach. Explicit expressions are derived for the spontaneous decay rate into the plasmon modes and for the atom-plasmon coupling as well as a plasmon-mediated atom-atom coupling. Phenomena due to the presence of losses in the metal are discussed. In case of two atoms, we observe Dicke sub- and superradiance resulting from their plasmon-mediated interaction. Based on this phenomenon, we propose a scheme for a deterministic two-qubit quantum ga…
We have developed a scalable method for coupling single color centers in diamond to plasmonic resonators and demonstrated Purcell enhancement of the single photon emission rate of nitrogen-vacancy (NV) centers. Our structures consist of single nitrogen-vacancy (NV) center-containing diamond nanoposts embedded in a thin silver film. We have utilized the strong plasmon resonances in the diamond-silver apertures to enhance the spontaneous emission of the enclosed dipole. The devices were realized by a combination of ion implantation and top-down nanofabrication techniques, which have enabled dete…
Quantum feedback can stabilize a two-level atom against decoherence (spontaneous emission), putting it into an arbitrary (specified) pure state. This requires perfect homodyne detection of the atomic emission, and instantaneous feedback. Inefficient detection was considered previously by two of us. Here we allow for a non-zero delay time $τ$ in the feedback circuit. Because a two-level atom is a nonlinear optical system, an analytical solution is not possible. However, quantum trajectories allow a simple numerical simulation of the resulting non-Markovian process. We find the effect of the tim…
We analyze the non-Markovian stochastic Schroedinger equation describing a particle subject to spontaneous collapses in space (in the language of collapse models), or subject to a continuous measurement of its position (in the language of continuous quantum measurement). For the first time, we give the explicit general solution for the free particle case (H = p^2/2m), and discuss the main properties. We analyze the case of an exponential correlation function for the noise, giving a quantitative description of the dynamics and of its dependence on the correlation time.
We study the applicability of collisional models for non-Markovian dynamics of open quantum systems. By allowing interactions between the separate environmental degrees of freedom in between collisions we are able to construct a collision model that allows to study quantum memory effects in open system dynamics. We also discuss the possibility to embed non-Markovian collision model dynamics into Markovian collision model dynamics in an extended state space. As a concrete example we show how using the proposed class of collision models we can discretely model non- Markovian amplitude damping of…
We develop a rigorous mathematically consistent description of PT symmetric optical systems by using second quantization. We demonstrate the possibility of significant spontaneous generation of photons in PT symmetric systems. Further we show the emergence of Hanbury-Brown Twiss (HBT) correlations in spontaneous generation. We show that the spontaneous generation determines decisively the nonclassical nature of fields in PT symmetric systems. Our work can be applied to other systems like plasmonic structure where losses are compensated by gain mechanisms.
We propose to detect non-Markovian decay of an exciton qubit coupled to multi-mode bosonic reservoir via shot-noise measurements. Non-equilibrium current noise is calculated for a quantum dot embedded inside a \QTR{it}{p-i-n} junction. An additional term from non-Markovian effect is obtained in the derivation of noise spectrum. As examples, two practical photonic reservoirs, photon vacuum with the inclusion of cut-off frequency and surface plasmons, are given to show that the noise may become super-Poissonian due to this non-Markovian effect. Utilizing the property of super-radiance is further…
We present a formulation of non-Markovian quantum trajectories for open systems from a measurement theory perspective. In our treatment there are three distinct ways in which non-Markovian behavior can arise; a mode dependent coupling between bath (reservoir) and system, a dispersive bath, and by spectral detection of the output into the bath. In the first two cases the non-Markovian behavior is intrinsic to the interaction, in the third case the non-Markovian behavior arises from the method of detection. We focus in detail on the trajectories which simulate real-time spectral detection of the…
We suggest and demonstrate an all-optical experimental setup to observe and engineer entanglement oscillations of a pair of polarization qubits in a non-Markovian channel. We generate entangled photon pairs by spontaneous parametric downconversion (SPDC), and then insert a programmable spatial light modulator in order to impose a polarization dependent phase-shift on the spatial domain of the SPDC output and to create an effective non-Markovian environment. Modulation of the enviroment spectrum is obtained by inserting a spatial grating on the signal arm. In our experiment, programmable oscill…
The ac Stark shift in the presence of spontaneous decay is typically considered to induce an effective dephasing with a scattering rate equal to $ Γ_s |Ω|^2/Δ^2 $, where $ Γ_s $ is the spontaneous decay rate, $ Ω$ is the laser transition coupling, and $ Δ$ is the detuning. We show that under realistic circumstances this dephasing rate may be strongly modifed due to non-Markovian behavior. The non-Markovian behavior arises due to an effective modification of the light-atom coupling in the presence of the ac Stark shift laser. An analytical formula for the non-Markovian ac Stark shift induced de…
We investigate the quantum recoil force acting on an excited atom close to the surface of a nonreciprocal photonic topological insulator (PTI). The main atomic emission channel is the unidirectional surface-plasmon propagating at the PTI-vacuum interface, and we show that it enables a spontaneous lateral recoil force that scales at short distance as $1/d^4$, where $d$ is the atom-PTI separation. Remarkably, the sign of the recoil force is polarization and orientation-independent, and it occurs in a translation-invariant homogeneous system in thermal equilibrium. Surprisingly, the recoil force …
Single surface plasmon polaritons are excited using photons generated via spontaneous parametric down-conversion. The mean excitation rates, intensity correlations and Fock state populations are studied. The observed dependence of the second order coherence in our experiment is consistent with a linear uncorrelated Markovian environment in the quantum regime. Our results provide important information about the effect of loss for assessing the potential of plasmonic waveguides for future nanophotonic circuitry in the quantum regime.
Intensity-intensity correlations are studied for light signals stemming from the spontaneous decay of surface plasmon oscillations, generated in the Kretschmann geometry. Non-classical photon statistics and the the transition from antibunching to bunching of the electron counts have been found experimentally and analysed on a new theoretical basis.
We investigate the two-plasmon spontaneous decay of a quantum emitter near single-walled carbon nanotubes (SWCNT) and graphene-coated wires (GCWs). We demonstrate efficient, enhanced generation of two-plasmon entangled states in SWCNTs due to the strong coupling between tunable guided plasmons and the quantum emitter. We predict two-plasmon emission rates more than twelve orders of magnitude higher than in free-space, with average lifetimes of a few dozens of nanoseconds. Given their low dimensionality, these systems could be more efficient for generating and detecting entangled plasmons in co…
In this paper we investigate how the dynamics of a two-level atom is affected by its interaction with the quantized near field of a plasmonic slab in relative motion. We demonstrate that for small separation distances and a relative velocity greater than a certain threshold, this interaction can lead to a population inversion, such that the probability of the excited state exceeds the probability of the ground state, corresponding to a negative spontaneous emission rate. It is shown that the developed theory is intimately related to a classical problem. The problem of quantum friction is analy…
As discovered by P. W. Anderson, excitations do not propagate freely in a disordered lattice, but, due to destructive interference, they localise. As a consequence when an atom interacts with a disordered lattice one indeed observes, a non-trivial excitation exchange between atom and lattice. Such non-trivial atomic dynamics will in general be characterised also by a non-trivial quantum information backflow, a clear signature of non-Markovian dynamics. To investigate the above scenario we consider a quantum emitter, or atom, weakly coupled to a uniform coupled-cavity array (CCA). If initially …
A generalization of the stochastic wave function method to quantum master equations which are not in Lindblad form is developed. The proposed stochastic unravelling is based on a description of the reduced system in a doubled Hilbert space and it is shown, that this method is capable of simulating quantum master equations with negative transition rates. Non-Markovian effects in the reduced systems dynamics can be treated within this approach by employing the time-convolutionless projection operator technique. This ansatz yields a systematic perturbative expansion of the reduced systems dynamic…
We present a formula to evaluate the spontaneous emission spectra of an atom in contact with a radiation field with non-Markovian effects. This formula is written in terms of a two-time correlation of system observables and the environmental correlation function, and depends on the distance between the emitting atom and the detector. As an example, we use it to analyze the fluorescence spectra of a two level atom placed as an impurity in a photonic crystal. The radiation field within those materials has a gap or discontinuity where electromagnetic modes cannot propagate in the stationary limit…
The state of a two-particle system is called entangled when its quantum mechanical wave function cannot be factorized in two single-particle wave functions. Entanglement leads to the strongest counter-intuitive feature of quantum mechanics, namely nonlocality. Experimental realization of quantum entanglement is relatively easy for the case of photons; a pump photon can spontaneously split into a pair of entangled photons inside a nonlinear crystal. In this paper we combine quantum entanglement with nanostructured metal optics in the form of optically thick metal films perforated with a periodi…
We explore the spontaneous generation and decay of quantum correlations between two identical atoms coupled to a common Markovian environment in the presence of electromagnetic field modes. For this purpose, we analyze the dynamics of quantum correlations by employing the concurrence, the trace quantum discord and the local quantum uncertainty, for collective Dicke states. It is shown that the collective damping and dipole-dipole interaction plays a key role in enhancing non-classical correlations during the process of intrinsic decoherence. The quantum correlations can be maintained over a lo…
We investigate the long-lived quantum coherence of two-level spontaneous emission models within structured environments. The population of the system under the asymptotic non-Markovian dynamics is linked to the spectral density of the reservoir through a general functional relation between them. We figure out explicitly the preservation of quantum coherence, via notions of entanglement and quantum discord, in connection with the spectral parameters of Ohmic class reservoirs and then show how to achieve them optimally. We expect these results to contribute towards reservoir engineering with the…
We devise new optical antennas that reduce the excited-state radiative lifetimes of emitters to the order of 100 femtoseconds while maintaining quantum efficiencies of about 80% at a broadband operation. Here, we combine metallic nanoparticles with planar dielectric structures and exploit design strategies from plasmonic nanoantennas and concepts from Cavity Quantum Electrodynamics to maximize the local density of states and minimize the nonradiative losses incurred by the metallic constituents. The proposed metallo-dielectric hybrid antennas promise important impact on various fundamental and…
We develop a general theoretical framework of integrated paired photon-plasmon generation through spontaneous wave mixing in nonlinear plasmonic and metamaterial nanostructures, rigorously accounting for material dispersion and losses in quantum regime through the electromagnetic Green function. We identify photon-plasmon correlations in layered metal-dielectric structures with 70% internal heralding quantum efficiency, and reveal novel mechanism of broadband generation enhancement due to topological transition in hyperbolic metamaterials.
We study non-Markovian enhancement effects in the spontaneous emission of a collective excitation in a linear chain of up to 100 qubits coupled to a 1D waveguide. We find that for a critical separation of qubits, the system exhibits super-superradiant (SSR) behavior leading to collective decay stronger than the usual Dicke superradiance. Here, time-delayed coherent quantum feedback effects are at play on top of the usual Dicke superradiance effects. We find a linear scaling for the SSR decay rate with increasing qubit number $N$ such that $Γ_{\rm SSR} \sim 2.277 N γ_0$, where $γ_0$ is the sing…
The spectrum width can be narrowed to a certain degree by decreasing the coupling strength for the two-level emitter coupled to the propagating surface plasmon. But the width can not be narrowed any further because of the loss of the photon out of system by spontaneous emission from the emitter. Here we propose a new scheme to construct a narrow-band source via a one-dimensional waveguide coupling with a three-level emitter. It is shown that the reflective spectrum width can be narrowed avoiding the impact of the loss. This approach opens up the possibility of plasmonic ultranarrow single-phot…
