Antonín Lukš

Principal squeezing of vacuum fluctuations

Abstract With regard to the squeezing detection process a more substantial definition of squeezing is proposed based on the sharpened Heisenberg uncertainty inequality. This notion involves the quadrature correlation and is rotationally invariant.

Quantum aspects of light propagation

Origin of Macroscopic Approach.- Macroscopic Theories and Their Applications.- Microscopic Theories.- Microscopic Models as Related to Macroscopic Descriptions.- Periodic and Disordered Media.- Conclusions.

Photoionization electron spectra in a system interacting with a neighboring atom

Photoelectron ionization spectra of a system interacting with a neighbor two-level atom are investigated using the Laplace-transform method. These spectra are typically composed of several peaks. Photoelectron ionization spectra conditioned by the measurement on the two-level atom show oscillations at the Rabi frequency. The presence of spectral zeros occurring periodically with the Rabi period is predicted. This phenomenon is analyzed in detail.

Quantum correlation and entanglement between an ionizing system and a neighboring atom interacting directly and via a quantized field

Quantum correlations between two neighbor atoms are studied. It is assumed that one atomic system comprises a single auto-ionizing level and the other atom does not contain any auto-ionizing level. The excitation of both atoms is achieved by the interaction with the same mode of the quantized field. It is shown that the long-time behavior of two atoms exhibits quantum correlations even when the atoms do not interact directly. This can be shown using the optical excitation of the neighbor atom. Also a measure of entanglement of two atoms can be applied after reduction of the continuum to two levels.

Fano zeros in photoelectron spectra of an autoionization system interacting with a neighboring atom.

Photoelectron ionization spectra of an autoionization system interacting with a neighboring two-level atom are studied using the method of canonical transformation. Conditions for the occurrence of a Fano zero are exactly derived, together with its frequency. Ionization spectra are typically composed of at most four peaks in this case. Sharp peaks occur not far from the Fano zero due to the confluence of bound-free coherences. Spectral peaks close to the Fano zero are suppressed. Also dynamical zeros appearing once per the Rabi period in conditioned photoelectron ionization spectra are observed.

Dynamics of nonclassical properties of two- and four-mode Bose–Einstein condensates

A two-mode Bose–Einstein condensate (BEC) prepared in a Fock state initially evolves due to the coupling of modes. The time evolution of nonclassical properties exhibits that inter-mode entanglement, single-mode and higher order antibunching are present. A four-mode BEC is considered with the initial minimum-energy Bloch states, and the nonclassical behaviour is confirmed.

Photoelectron spectra in an autoionization system interacting with a neighboring atom

Photoelectron ionization spectra of an autoionization system with one discrete level interacting with a neighbor two-level atom are discussed. The formula for long-time ionization spectra is derived. According to this formula, the spectra can be composed of up to eight peaks. Moreover, the Fano-like zeros for weak optical pumping are identified in these spectra. The conditional ionization spectra depending on the state of the neighbor atom exhibit oscillations at the Rabi frequency. Dynamical spectral zeros occurring once per the Rabi period are revealed in these spectra.

Linear coupling, loss and gain of counterpropagating beams

We investigate counterpropagation of the two-mode input state in a corrugated waveguide, which reproduces a photonic band-gap structure. First assuming a gain medium, we model a distributed feedback laser as an amplifier. From this case we pass to the attenuator, which corresponds to a lossy medium. We determine the transmission and fidelity spectra for the waveguide in the dependence on a mismatch coefficient and a measure of losses.

Entanglement between an autoionizing system and a neighboring atom

Entanglement between two electrons belonging to an auto-ionization system and a neighbor two-level atom produced by the dipole-dipole interaction is studied. The entanglement is quantified using the quadratic negativity of a bipartite system including the continuum of states. Suitable conditions for the generation of highly entangled states of two electrons are revealed. Internal structure of the entanglement is elucidated using the spectral density of quadratic negativity.

Surface Spontaneous Parametric Down-Conversion

Surface spontaneous parametric down-conversion is predicted as a consequence of continuity requirements for electric- and magnetic-field amplitudes at a discontinuity of chi;{(2)} nonlinearity. A generalization of the usual two-photon spectral amplitude is suggested to describe this effect. Examples of nonlinear layered structures and periodically poled nonlinear crystals show that surface contributions to spontaneous down-conversion can be important.