We show that no distillation protocol for Gaussian quantum states exists relies on (i) arbitrary local unitary operations preserve the character of state and (ii) homodyne detection together with classical communication postprocessing by means two symmetric identically prepared copies. This is in contrast to finite-dimensional case, where entanglement can be distilled an iterative using copies at a time. The ramifications distribution over large distances will outlined. also comment...

Macroscopic quantum electrodynamics - Concepts and applications In this article, we review the principles of macroscopic discuss a variety theory to medium-assisted atom-field coupling dispersion forces. The generalises standard mode expansion electromagnetic fields in free space allow for presence absorbing bodies. We show that provides link between isolated atomic systems magnetoelectric bodies, serves as an important tool understanding surface-assisted relaxation effects intimately...

We introduce a protocol that maps finite-dimensional pure input states onto approximately Gaussian in an iterative procedure. This can be used to distill highly entangled bi-partite from supply of weakly states. The entire procedure requires only the use passive optical elements and photon detectors solely distinguish between presence absence photons.

We present a quantization scheme for the electromagnetic field interacting with atomic systems in presence of dispersing and absorbing magnetodielectric media, including left-handed material having negative real part refractive index. The theory is applied to spontaneous decay two-level atom at center spherical free-space cavity surrounded by matter overlapping band-gap zones. Results both big small cavities are presented, problem local-field corrections within real-cavity model addressed.

Starting from the quantized version of Maxwell's equations for electromagnetic field in an arbitrary linear Kramers-Kronig dielectric, Heisenberg motion a two-level atom resonantly coupled to radiation presence dispersive and absorbing dielectric bodies are derived. The theory is applied problem spontaneous decay excited atoms media. rate calculated (Glauber-Lewenstein) real-cavity model, comparison with recently studied (Clausius-Mosotti) virtual-cavity model [S. Scheel, L. Kn\"oll, D.-G....

Recently a quantization scheme for the phenomenological Maxwell theory of full electromagnetic field in an inhomogeneous three-dimensional, dispersive, and absorbing dielectric medium has been developed applied to system consisting two infinite half-spaces with common planar interface (H.T. Dung, L. Kn\"oll, D.-G. Welsch, Phys. Rev. A 57, 3931 (1998)). Here we show that scheme, which is based on classical Green-tensor integral representation field, applies any medium. For this purpose prove...

We critically discuss whether and under what conditions Lifshitz theory may be used to describe thermal Casimir-Polder forces on atoms or molecules. An exact treatment of the atom-field coupling reveals that for a ground-state atom (molecule), terms associated with virtual-photon absorption lead deviation from traditional result; they are identified as signature nonequilibrium dynamics. Even equilibrium force thermalized (molecule) overestimated when using polarizability instead its counterpart.

Recent high-resolution absorption spectroscopy on excited excitons in cuprous oxide [Nature (London) 514, 343 (2014)] has revealed significant deviations of their spectrum from that the ideal hydrogen-like series. Here we show complex band dispersion crystal, which determines kinetic energy electrons and holes, strongly affects exciton binding energy. Specifically, nonparabolicity is main cause deviation hydrogen Experimental data collected electric fields validate assignment to dispersion.

We discuss the impact of gain and loss on evolution photonic quantum states find that PT-symmetric optics in gain/loss systems is not possible. Within framework macroscopic electrodynamics we show are associated with non-compact compact operator transformations, respectively. This implies a fundamentally different way which correlations between system reservoir built up destroyed.

In this paper, we provide necessary and sufficient conditions for a completely positive trace-preserving (CPT) map to be decomposable into convex combination of unitary maps. Additionally, set out define proper distance measure between given CPT the random maps, methods calculating it. way one could determine whether non-classical error mechanisms such as spontaneous decay or photon loss dominate over classical uncertainties, example, in phase parameter. The present paper is step towards...

This review surveys the physical principles and recent developments in manufacturing single-photon sources. Special emphasis is placed on important potential applications such as linear optical quantum computing (LOQC), key distribution (QKD) metrology that drive development of these sources single photons. We discuss quantum-mechanical properties light prepared a state definite photon number compare it with coherent shows Poissonian numbers. examine how fidelity directly influences ability...

Polarizable atoms and molecules experience the Casimir-Polder force near magnetoelectric bodies, a that is induced by quantum fluctuations of electromagnetic field matter. Atoms in relative motion to surface an additional velocity-dependent force. We present full quantum-mechanical treatment this identify generalized Doppler effect, time delay between photon emission reabsorption, R\"ontgen interaction as its three sources. For ground-state atoms, very small always decelerating, hence...

We formulate macroscopic quantum electrodynamics in the most general linear, absorbing media. In particular, Onsager reciprocity is not assumed to hold. The field quantization based on source-quantity representation of electromagnetic terms dyadic Green's tensor. For media with a nonlocal response, description complex conductivity tensor employed. As an alternative description, we introduce permittivity, permeability and magnetoelectric susceptibilities obtain explicitly duality-invariant...

In this article we analyze the Casimir-Polder interaction of atoms with a solid grating and an additional repulsive between in presence external laser source. The combined potential landscape above body is probed locally by diffraction Bose-Einstein condensates. Measured efficiencies reveal information about shape allow us to discern models based on pairwise-summation (Hamaker) approach Lifshitz theory.

We study the spontaneous emission of an excited atom close to optical nanofiber and resulting scattering forces. For a suitably chosen orientation atomic dipole, pattern becomes asymmetric resonant Casimir--Polder force parallel fiber axis arises. simple model case, we show that such lateral is due interaction circularly oscillating dipole moment with its image inside material. With energy being constant in direction, predicted does not derive from potential usual way. Our results have...

The aim of this paper is to revisit the calculation atom-surface quantum friction in field theory formulation put forward by Barton (2010 New J. Phys. 12 113045). We show that power dissipated into excitations and associated force depend on how atom boosted from being initially at rest a configuration which it moving constant velocity (v) parallel planar interface. In addition, we point out there subtle cancellation between one-photon part two-photon dissipating power, resulting leading...

We use two-color pump-probe spectroscopy to study Rydberg excitons in Cu$_2$O the presence of free carriers injected by above-band-gap excitation. Already at plasma densities $\rho_\text{eh}$ below one hundredth electron-hole pair per \textmu m$^{3}$, exciton absorption lines are bleached while their energies remain constant, until they finally disappear, starting from highest observed principal quantum number $n_\text{max}$. As confirmed calculations, band gap is reduced many-particle...

Coherent optical control of individual particles has been demonstrated both for atoms and semiconductor quantum dots. Here we demonstrate the emergence coherent effects in Rydberg excitons bulk Cu_{2}O. Because spectral proximity between two adjacent exciton states, a single-frequency laser may pump resonances with little dissipation from detuning. As consequence, additional appear absorption spectrum that correspond to dressed states consisting levels coupled excitonic vacuum, forming...

We propose a realistic semiconductor system containing bound states in the continuum (BICs) which allows for practical realization. By varying confinement strength of excitons cuprous oxide quantum wells, we show that long-lived Rydberg confined electron-hole pairs appear background. The accuracy calculations linewidths based on coupled-channel Schr\"odinger equation with three channels and only few basis is confirmed by numerically exact solution employing B-spline complex...

The influence of losses in the interferometric generation and transmission continuous-variable entangled light is studied, with special emphasis on Gaussian states. Based theory quantum-state transformation at absorbing dielectric devices, amount entanglement quantified by means relative-entropy measure. Upper bounds distance to set separable states are calculated. Compared measure, can substantially overestimate entanglement. In particular, they do not show drastic decrease increasing mean...

We study single- and two-atom van der Waals interactions of ground-state atoms which are both polarizable paramagnetizable in the presence magnetoelectric bodies within framework macroscopic quantum electrodynamics. Starting from an interaction Hamiltonian that includes particle spins, we use leading-order perturbation theory to express potentials terms polarizability magnetizability atom(s). To allow for embedded media, also include local-field corrections via real-cavity model. The general...