Physical Review A

The π -phase shift between |F=1,m_F=0⟩ and |F=2,m_F=0⟩ states for an adiabatic rotation of a magnetic field observed in Ramsey atom interferometry arises from the negative sign of the transition amplitude between the |1,0⟩ and |2,0⟩ states when the wave functions are rotated to the o...

Quantum random walks have received much interest due to their nonintuitive dynamics, which may hold the key to a new generation of quantum algorithms. What remains a major challenge is a physical realization that is experimentally viable and not limited to special connectivity criteria. We present a...

We propose a realistic protocol to generate entanglement between quantum memories at neighboring nodes in hybrid quantum repeaters. Generated entanglement includes only one type of error, which enables efficient entanglement distillation. In contrast to the known protocols with such a property, our ...

We determine the conditions under which topological order survives a rapid quantum quench. Specifically, we consider the case where a quantum spin system is prepared in the ground state of the toric code model and, after the quench, it evolves with a Hamiltonian that does not support topological ord...

We present a system for the simulation of quantum phase transitions of collective internal qubit and phononic states with a linear crystal of trapped ions. The laser-ion interaction creates an energy gap in the excitation spectrum, which induces an effective phonon-phonon repulsion and a Jaynes-Cumm...

We demonstrate a quadratic phase gate for one-way quantum computation in the continuous-variable regime. This canonical gate, together with phase-space displacements and Fourier rotations, completes the set of universal gates for realizing any single-mode Gaussian transformation such as arbitrary sq...

Isolated nuclear spins provide a promising building block for quantum information science, motivating development of techniques to characterize, control, and detect them in suitable systems. Working with the nitrogen-vacancy center in diamond, we demonstrate robust initialization, manipulation, and ...

Recently, the molecular cation PtH⁺ was suggested as a promising candidate for the experimental search for the electron electric dipole moment. For estimating the sensitivity of the experiment on the cation and for interpretation of the experimental results, it is necessary to calculate an effecti...

A high-resolution (ΔE∼55 meV) trap-based positron beam has been used to measure absolute scattering cross sections for the excitation of the resolved 2 ¹S,P states of helium at energies between threshold and 38 eV. The experimental integral cross sections, which have typical uncertainties...

A quantum-mechanical approach to ion-molecule collisions is presented. It involves a separation of molecular geometry and collision dynamics and enables the use of the basis generator method developed for ion-atom collisions with relatively minor modifications. As a first application, we consider th...

We demonstrate experimentally the efficient fusion neutron generation from Coulomb explosion (CE) of laser irradiated large-size heteronuclear deuterated methane clusters. A conversion efficiency of 2.1×10⁶ neutrons/J of incident laser energy is obtained with a 120 mJ, 70 fs laser pulse. It is ...

Numerical solution of the time-dependent Schrödinger equation for a two-dimension model of H₂ ionization by intense ultrashort (few cycles) extreme ultraviolet (XUV) laser pulses are presented to compare linear and circular polarization angular distributions for aligned molecules. Both ground (X...

A method for complete characterization of the waveform of individual few-cycle laser pulses is presented. By analyzing the “left” and “right” asymmetries of high-energy photoelectrons along the polarization axis using the recently developed quantitative rescattering theory, we show that the ...

We derive the two-channel (TC) description of the photoassociation (PA) process in the presence of a magnetic Feshbach resonance and compare to full coupled multichannel calculations for the scattering of ⁶Li-⁸⁷Rb . Starting from a similar approach as that of Pellegrini [Phys. Rev. Lett. 101, 0532...

The Auger transitions to different repulsive doubly charged molecular ion states are separated by measuring the angular resolved photoelectrons and Auger electrons in coincidence in the molecular fixed frame. The separation is achieved by comparing the experimental Auger-electron angular distributio...

We show the existence of a permanent molecular planar alignment in field-free conditions. We present different control strategies using shaped laser pulses to reach this state. The strategies are robust with respect to the temperature and can be implemented with the state of the art technology. They...

We analyzed the discrepancy of the angular dependence of strong-field ionization for CO₂ among the different theoretical calculations and experiments. Using a more accurate ground-state wave function of CO₂ in the asymptotic region, we showed that the accuracy in the earlier tunneling ionization...

We study the interplay of quantum statistics, strong interactions, and finite temperatures in the two-component (spinor) Bose gas with repulsive delta-function interactions in one dimension. Using the Thermodynamic Bethe Ansatz, we obtain the equation of state, population densities, and local densit...

Recently demonstrated superconducting atom chips provide a platform for trapping atoms and coupling them to solid-state quantum systems. Controlling these devices requires a full understanding of the supercurrent distribution in the trapping structures. For type-II superconductors, this distribution...

We demonstrate a two-dimensional atom interferometer in a harmonic magnetic waveguide using a Bose-Einstein condensate. Such an interferometer could measure rotation using the Sagnac effect. Compared to free space interferometers, larger interactions times and enclosed areas can in principle be achi...

Dispersive shock waves (DSWs) are studied theoretically in the context of two-dimensional (2D) supersonic flow of a superfluid. Employing Whitham averaging theory for the repulsive Gross-Pitaevskii (GP) equation, suitable jump and entropy conditions are obtained for an oblique DSW, a fundamental bui...

It is shown that the jump in the momentum distribution of Fermi gases evolves smoothly for small and intermediate times once an interaction between the fermions is suddenly switched on. The jump does not vanish abruptly. The loci in momentum space where the jumps occur are those of the noninteractin...

Whether a spin-1/2 Fermi gas will become ferromagnetic as the strength of repulsive interaction increases is a long-standing controversial issue. Recently this problem has been studied experimentally by Jo [Science 325, 1521 (2009)] in which the authors claim a ferromagnetic transition is observed....

We propose to implement a sub-shot-noise matter-wave interferometer via the stimulated dissociation of a molecular Bose-Einstein condensate and study the collisional loss of atom-molecule coherence during its phase-acquisition time. The obtained n -atom states are two-atom [SU(1,1)] coherent states...

Dispersion and dissipation are inherent to electromagnetic wave propagation in metamaterials. We show that these inherent limitations can be overcome by a self-induced transparency pulse that stably propagates through a metamaterial sparsely doped with resonantly absorbing dopants. This pulse has th...

We show that when an electron or photon propagates in a cylindrically symmetric waveguide, its spin angular momentum (SAM) and its orbital angular momentum (OAM) interact. Remarkably, we find that the dynamics resulting from this spin-orbit interaction are quantitatively described by a single expres...

An exact solution for the problem of interaction between whispering gallery modes of spherical microresonators and a single dipole is presented. It is predicted that experimentally observed spectral doublets associated with this interaction are a part of a triplet whose third component has yet to be...

We report a unified representation of the spatial and angular Goos-Hänchen and Imbert-Fedorov shifts that occur when a light beam reflects from a plane interface. We thus reveal the dual nature of spatial and angular shifts in optical beam reflection. In the Goos-Hänchen case we show theoretically...

The Raman gain of a probe light in a three-state Λ scheme placed into a defect of a one-dimensional photonic crystal is studied theoretically. We show that there exists a pump intensity range, where the transmission and reflection spectra of the probe field exhibit simultaneously occurring narrow...

We suggest possibilities for manipulation and ground-state cooling of micromechanical oscillators by resonant coupling of the mirror vibrations to narrow optical transitions of a designed material ensemble within a cavity mode. Particles, modeled as a two-level ensemble, create intracavity narrow ba...

We study the statistics of quantum interference for completely positive maps. We calculate analytically the mean interference and its second moment for finite-dimensional quantum systems interacting with a simple environment consisting of one or several spins (qudits). The joint propagation of the e...

We show that the usefulness of the thermal state of a specific spin-lattice model for measurement-based quantum computing exhibits a transition between two distinct “phases”—one in which every state is a universal resource for quantum computation, and another in which any local measurement seq...

Quantum random walks have received much interest due to their nonintuitive dynamics, which may hold the key to a new generation of quantum algorithms. What remains a major challenge is a physical realization that is experimentally viable and not limited to special connectivity criteria. We present a...

We propose a realistic protocol to generate entanglement between quantum memories at neighboring nodes in hybrid quantum repeaters. Generated entanglement includes only one type of error, which enables efficient entanglement distillation. In contrast to the known protocols with such a property, our ...

The low-rotational lines of the A ²Π-X ²Σ⁺(0,0) band system of the odd isotopologue of strontium monofluoride, ⁸⁷SrF , were recorded and analyzed. The ⁸⁷Sr(I=9/2) magnetic hyperfine interaction is significant only in the |Ω|=1/2 spin-orbit component of the A ²Π state. Optical tran...

The pressure broadening and shift rates for the cesium D₁ (6 ²P_1/2←6 ²S_1/2) transition with the noble gases and N₂ , H₂ , HD, D₂ , CH₄ , C₂H₆ , CF₄ , and ³He were obtained for pressures less than 300 torr at temperatures under 65 °C by means of laser absorption spectroscopy. T...

The scattering wave function and the transition amplitude for the two-body Coulomb problem are written as power series of the Sommerfeld parameter. Making use of a mathematical study of the nth derivatives of Kummer function with respect to its first parameter, the series coefficients are expresse...

We report improved precision measurements of the van der Waals potential strength (C₃) for Na atoms and a silicon-nitride (SiN_x) surface. We studied diffraction from nanofabricated gratings with a particular “magic” open fraction that allows us to determine C₃ without the need for separate...

In order to characterize the statistical aspect of the energy loss in particle penetration, Bohr developed a kinetic theory and applied it to a beam of fast α particles interacting with free electrons. The present study rests on this classical theory of collisional straggling, and it is implement...

We describe a low-pressure flow-through apparatus for generating hyperpolarized ¹²⁹Xe and report its performance by examining both the output ¹²⁹Xe polarization P_Xe by NMR and the in situ Rb polarization profile by optically detected electron paramagnetic resonance. The polarizer is based on a...

We propose a scheme to trap cold atoms (or molecules) by using an improved red- or blue-detuned far-field optical trap, which is formed by an optical system composed of a binary phase plate and a circular aperture illuminated by a plane light wave. We calculate the relative intensity distribution of...

Numerical solution of the time-dependent Schrödinger equation for a two-dimension model of H₂ ionization by intense ultrashort (few cycles) extreme ultraviolet (XUV) laser pulses are presented to compare linear and circular polarization angular distributions for aligned molecules. Both ground (X...

Population transfer to the excited electronic state E ¹Σ_g of Li₂ by transform limited delayed femtosecond pulses has been investigated. The validity of the usual neglect of some field-molecule coupling terms in such transfers, accomplished using counterintuitively ordered pulses through “ad...

We investigate magnetism and quantum phase transitions in a one-dimensional system of integrable spin-1 bosons with strongly repulsive density-density interaction and antiferromagnetic spin-exchange interaction via the thermodynamic Bethe ansatz method. At zero temperature, the system exhibits three...

We investigate the exact nature of the superfluid–to–Mott-insulator crossover for interacting bosons on an optical lattice in a one-dimensional harmonic trap by high-precision density-matrix renormalization-group calculations. The results reveal an intermediate regime characterized by a cascade ...

We investigate the phenomenon of fermionic pairing with mismatched Fermi surfaces in a two-species system in the presence of Feshbach resonance, where the resonantly paired fermions combine to form bosonic molecules. We observe that the Feshbach parameters control the critical temperature of the gap...

Coherence properties of light beams generated by optical parametric oscillators (OPOs) are discussed in the region of threshold. Analytic expressions, that are valid throughout the threshold region, for experimentally measurable quantities such as the mean and variance of photon number fluctuations,...

Cold atoms in an optical lattice execute Bloch-Zener oscillations when they are accelerated. We have performed a theoretical investigation into the case when the optical lattice is the intracavity field of a driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we find that th...

In this paper, the interface between two transformation media or between a transformation medium and vacuum is studied. Strictly from the transformation optics point of view, the consequences of the boundary conditions at such interfaces are addressed in two different ways. First, we analyze a restr...

We report on a teleportation scheme, in which a controllable orbital angular momentum (OAM) generator is teleported. Via our scheme, Alice is able to—according to another independent photon’s spin state (polarization) sent by Carol—electrically control the remote OAM generation on Bob’s phot...

We report on the experimental observation of two-dimensional surface solitons residing at the interface between a homogeneous square lattice and a superlattice that consists of alternating “deep” and “shallow” waveguides. By exciting single waveguides in the first row of the superlattice, we...

Several wave-function approximations describing spontaneous parametric down-conversion can be found in the literature. Basically all cases are derived from the standard Hamiltonian for parametric down-conversion. Most frequently, particular cases describing collinear or paraxial approximations are d...

Inconsistencies are pointed out in the usual quantum versions of the classical linear Boltzmann equation constructed for a quantized test particle in a gas. These are related to the incorrect formal treatment of momentum decoherence. We prove that ideal collisions with the molecules would result in ...

Quantum mechanical phases arising from a periodically varying Hamiltonian are considered. These phases are derived from the eigenvalues of a stationary, “dressed” Hamiltonian that is able to treat internal atomic or molecular structure in addition to the time variation. In the limit of an adiaba...

We show relations between superposition of macroscopically distinct states and entanglement. These relations lead to the important conclusion that if a state contains superposition of macroscopically distinct states, the state also contains large multipartite entanglement in terms of several measures. Such multipartite entanglement property also suggests that if a state contains superposition of macroscopically distinct states, a measurement on a single particle drastically changes the state of macroscopically many other particles, as in the case of the N-qubit GHZ state.

We demonstrate how to simulate both discrete and continuous stochastic evolution of a quantum many body system subject to measurements using matrix product states. A particular, but generally applicable, measurement model is analyzed and a simple representation in terms of matrix product operators is found. The technique is exemplified by numerical simulations of the anti-ferromagnetic Heisenberg spin-chain model subject to various instances of the measurement model. In particular we focus on local measurements with small support and non-local measurements which induces long range correlations.

One of the last open problems concerning two qubits in a pure state is to find the exact local content of their correlation, in the sense of Elitzur, Popescu and Rohrlich (EPR2) [Phys. Lett. A 162, 25 (1992)]. We propose a new EPR2 decomposition that allows us to prove, for a wide range of states \kety(q)=cosq\ket00+sinq\ket11, that their local content is [`(pL)](q) = cos2q. We also share reflections on how to possibly extend our result to all two-qubit pure states.

We present a comprehensive investigation of nonideal continuous-variable quantum teleportation implemented with entangled non-Gaussian resources. We discuss in a unified framework the main decoherence mechanisms, including imperfect Bell measurements and propagation of optical fields in lossy fibers, applying the formalism of the characteristic function. By exploiting appropriate displacement strategies, we compute analytically the success probability of teleportation for input coherent states, and two classes of non-Gaussian entangled resources: Two-mode squeezed Bell-like states (that include as particular cases photon-added and photon-subtracted de-Gaussified states), and two-mode squeezed cat-like states. We discuss the optimization procedure on the free parameters of the non-Gaussian resources at fixed values of the squeezing and of the experimental quantities determining the inefficiencies of the non-ideal protocol. It is found that non-Gaussian resources enhance significantly the efficiency of teleportation and are more robust against decoherence than the corresponding Gaussian ones. Partial information on the alphabet of input states allows further significant improvement in the performance of the nonideal teleportation protocol.

The dynamics behavior of output squeezing and entanglement is investigated, based on the off-resonant interaction of a four-level atom with a low-Q cavity and two classical fields. By means of the input-output theory, we show that the two-mode squeezing and entanglement of the output fields can always exist. It is found that the maximum entanglement is insensitive to the cavity decay rate, but can be optimized by adjusting the ratio between the effective coupling constants.

Feedback control protocols can stabilize and enhance the operation of quantum devices, but unavoidable delays in the feedback loop adversely affect their performance. We introduce a quantum control methodology, combining open-loop control with quantum filtering, which is not constrained by feedback delays. For the problems studied (rapid purification and rapid measurement) we analytically derive lower bounds on the control performance that are comparable with the best corresponding bounds for feedback protocols.

It is revealed that ensembles consisting of multipartite quantum states can exhibit different kinds of nonlocalities. An operational measure is introduced to quantify nonlocalities in ensembles consisting of bipartite quantum states. Various upper and lower bounds for the measure are estimated and the exact values for ensembles consisting of mutually orthogonal maximally entangled bipartite states are evaluated.

One-way quantum computing is an important and novel approach to quantum computation. By exploiting the existing particle-particle interactions, we report the first experimental realization of the complete process of deterministic one-way quantum Deutsch-Josza algorithm in NMR, including graph state preparation, single-qubit measurements and feed-forward corrections. The findings in our experiment may shed light on the future scalable one-way quantum computation.

We propose an algorithm to simulate interacting fermions on a two dimensional lattice. The approach is an extension of the entanglement renormalization technique [Phys. Rev. Lett. 99, 220405 (2007)] and the related multi-scale entanglement renormalization ansatz. Benchmark calculations for free and interacting fermions on lattices ranging from 6times;6 to 162times;162 sites with periodic boundary conditions confirm the validity of this proposal.

Spin relaxation due to atom-atom collisions is measured for magnetically trapped erbium and thulium atoms at a temperature near 500nbsp;mK. The rate constants for Er-Er and Tm-Tm collisions are 3.0times;10-10nbsp; and 1.1times;10-10nbsp;, respectively, 2-3 orders of magnitude larger than those observed for highly magnetic S-state atoms. This is strong evidence for an additional, dominant, spin relaxation mechanism, electronic interaction anisotropy, in collisions between these "submerged-shell" L 0 atoms. These large spin relaxation rates imply that evaporative cooling of these atoms in a magnetic trap will be highly inefficient.

A theoretical study of the subshell photoionization of the Xe atom endohedrally confined in \ful is presented. Powerful hybridization of the Xe 5s state with the bottom edge of \ful p band is found that induces strong structures in the 5s ionization, causing the cross section to differ significantly from earlier results that omit this hybridization. The hybridization also affects the angular distribution asymmetry parameter of Xe 5p ionization near the Cooper minimum. The 5p cross section, on the other hand, is greatly enhanced by borrowing considerable oscillator strength from the \ful giant plasmon resonance via the atom-fullerene dynamical interchannel coupling. Beyond the \ful plasmon energy range the atomic subshell cross sections display confinement-induced oscillations in which, over the large 4d shape resonance region, the dominant 4d oscillations induce their "clones" in all degenerate weaker channels known as correlation confinement resonances.

We study resonant nonlinear magneto-optic rotation (NMOR) in a paraffin-coated Rb vapor cell as the magnetic field is swept. At low sweep rates, the nonlinear rotation appears as a narrow resonance signal, with a linewidth of about "300 mG" (2ptimes;420 Hz). At high sweep rates, the signal shows transient response with an oscillatory decay. The decay time constant is of order 100 ms. The behavior is different for transitions starting from the lower or the upper hyperfine level of the ground state because of optical pumping effects.

We consider a time-dependent optical lattice with staggered particle current in the tight-binding regime and show that it can be described by a time-independent effective lattice model with an artificial staggered magnetic field. The low energy description of a single-component fermion in this lattice at half-filling is provided by two copies of ideal two-dimensional massless Dirac fermions. The Dirac cones are generally anisotropic and can be tuned by the external staggered flux \p. For bosons, the staggered flux modifies the single-particle spectrum such that in the weak coupling limit, depending on the flux \p, distinct superfluid phases are realized. We discuss their properties, establish the nature of the phase transitions between them and use Bogoliubov theory to determine their excitation spectra. We then study the generalized superfluid-Mott insulator transition in the presence of the staggered flux and establish the complete phase diagram. Finally, we obtain the momentum distribution of the distinct superfluid phases, which provide a clear experimental signature of each phase in ballistic expansion experiments.

We report on storage of images in atomic coherences, driven by electromagnetically-induced transparency in a doped solid. We demonstrate image storage times up to the regime of milliseconds, i.e. more than two orders of magnitude larger than in gaseous media. Our data also reveal an improvement in the spatial resolution of the retrieved images by a factor of 40. The long storage times become possible by applying additional radio-frequency pulse sequences to drive rephasing of the atomic coherences. Moreover, the perturbing effect of atomic diffusion (which significantly limits image storage times in gases) is absent in the solid. In addition, we monitored pronounced oscillations in the intensity of the retrieved image vs. the storage time. These oscillations are due to beating of dark-state polaritons. All of these results demonstrate the superior properties of coherently-driven optical data storage in solids.

Antiferromagnetism of ultracold fermions in an optical lattice can be detected by Bragg diffraction of light, in analogy to the diffraction of neutrons from solid state materials. A finite sublattice magnetization will lead to a Bragg peak from the (1/2nbsp;1/2nbsp;1/2) crystal plane with an intensity depending on details of the atomic states, the frequency and polarization of the probe beam, the direction and magnitude of the sublattice magnetization, and the finite optical density of the sample. Accounting for these effects we make quantitative predictions about the scattering intensity and find that with experimentally feasible parameters the signal can be readily measured with a CCD camera or a photodiode and used to detect antiferromagnetic order.

We present a numerical study of the one-dimensional BCS-BEC crossover of a spin-imbalanced Fermi gas. The crossover is described by the Bose-Fermi resonance model in a real space representation. Our main interest is in the behavior of the pair correlations, which, in the BCS limit, are of the Fulde-Ferrell-Larkin-Ovchinnikov type, while in the BEC limit, a superfluid of diatomic molecules forms that exhibits quasi-condensation at zero momentum. We use the density matrix renormalization group method to compute the phase diagram as a function of the detuning of the molecular level and the polarization. As a main result, we show that FFLO-like correlations disappear well below full polarization close to the resonance. The critical polarization depends on both the detuning and the filling.

A three mode opto-acoustic parametric amplifier (OAPA) is created when two orthogonal optical modes in a high finesse optical cavity are coupled via an acoustic mode of the cavity mirror. Such interactions are predicted to occur in advanced long baseline gravitational wave detectors. They can have high positive gain, which leads to strong parametric instability. Here we show that a novel optical feedback scheme can enhance or suppress the parametric gain of an OAPA, allowing exploration of three-mode parametric interactions, especially in cavity systems that have insufficient optical power to achieve spontaneous instability. We derive analytical equations and show that optical feedback is capable of controlling predicted instabilities in advanced gravitational wave detectors within a time scale of 1 ~ 10 seconds.

Propagation equations for optical pulses are needed to assist in describing applications in ever more extreme situations - including those in metamaterials with linear and nonlinear magnetic responses. Here I show how to derive a single first order propagation equation using a minimum of approximations and a straightforward "factorization" mathematical scheme. The approach generates exact coupled bi-directional equations, after which it is clear that the description can be reduced to a single uni-directional first order wave equation by means of a simple "slow evolution" approximation, where the optical pulse changes little over the distance of one wavelength. It also also allows a direct term-to-term comparison of an exact bi-directional theory with the approximate uni-directional theory.

We present a theoretical study of the dynamics of a light pulse propagating through a multi-layer system consisting of alternating blocks of EIT media and vacuum. We study the effect of a dynamical modulation of the EIT control field on the shape of the wavepacket. Interesting effects due to the group velocity mismatch at the interfaces are found. Modulation schemes that can be realized in ultracold atomic samples with standard experimental techniques are proposed and discussed. Calculations are performed using a modified slowly varying envelope approximation of the Maxwell-Bloch equations and are compared to an effective description based on a continuity equation for the polariton flow.

We consider a mixture consisting of two species of spherical nanoparticles dispersed in a liquid medium. We show that with an appropriate choice of refractive indices and particle diameters, it is possible to observe the phenomenon of optical soliton bistability in two spatial dimensions in a broad beam power range. Previously, this possibility was ruled out in the case of a single-species colloid. As a particular example, we consider the system of hydrophilic silica particles and gas bubbles generated in the process of electrolysis in water. The interaction of two soliton beams can lead to switching of the lower branch solitons to the upper branch, and the interaction of solitons from different branches is phase-independent and always repulsive.

We study the spatial coherence properties of the entangled two-photon field produced by parametric down-conversion (PDC) when the pump field is, spatially, a partially coherent beam. By explicitly treating the case of a pump beam of the Gaussian Schell-model type, we show that in PDC the spatial coherence properties of the pump field get entirely transferred to the spatial coherence properties of the down-converted two-photon field. As one important consequence of this study, we find that, for two-qubit states based on the position correlations of the two-photon field, the maximum achievable entanglement, as quantified by concurrence, is bounded by the degree of spatial coherence of the pump field. These results could be important by providing a means of controlling the entanglement of down-converted photons by tailoring the degree of coherence of the pump field.

Optical Sommerfeld-Brillouin precursors significantly ahead of a main field of comparable amplitude have been recently observed in an opaque medium with an electromagnetically induced transparency window [Wei et al., Phys. Rev. Lett. 103, 093602 (2009)]. We theoretically analyze in this paper the somewhat similar results obtained when the transparency is induced by the propagating field itself and we establish an approximate analytic expression of the time-delay of the main-field arrival, which fits fairly well the result obtained by numerically solving the Maxwell-Bloch equations.

Compression of UV femtosecond laser pulses focused into a gas cell filled with xenon is reported numerically. With a large negative Kerr index and normal dispersion, xenon promotes temporal modulational instability (MI) which can be monitored to shorten ~ 100 fs pulses to robust, singly-peaked waveforms exhibiting a fourfold compression factor. Combining standard MI theory with a variational approach allows us to predict the beam parameters suitable for efficient compression. At powers 30 MW, nonlinear dispersion is shown to shift the pulse temporal profile to the rear zone.

We present a procedure for the measurement of quadrature components of an electromagnetic field in the far-field as an alternative to the traditional approach based on the homodyne detection (HD) technique. For that we suggest to use coherent sources such as phase-locked lasers or optical parametric oscillators operating above threshold. Then we show how to arrange the detection procedure in the far field that is exactly or partly equivalent to the HD. Our scheme can be applied for both the classical and non-classical fields. The potential of the procedure is illustrated by an example which utilizes the pixellised sources of the non-classical light. As an integral part of our investigation we develop a theory of the pixellised source of the spatio-temporally squeezed light.