We theorize an enhanced and switchable spin Hall effect (SHE) of light near the Brewster angle on reflection and demonstrate it experimentally. The obtained spin-dependent splitting reaches 3200 nm near the Brewster angle, which is 50 times larger than the previously reported values in refraction. We find that the amplifying factor in weak measurement is not a constant, which is significantly different from that in refraction. As an analogy of SHE in an electronic system, a switchable spin accumulation in SHE of light is detected. We were able to switch the direction of the spin accumulations by slightly adjusting the incident angle.

Atmospheric turbulence generally affects the resolution and visibility of an image in long-distance imaging. In a recent quantum ghost imaging experiment [P. B. Dixon et al., Phys. Rev. A 83, 051803 (2011)], it was found that the effect of the turbulence can nevertheless be mitigated under certain conditions. This paper gives a detailed theoretical analysis to the setup and results reported in the experiment. Entangled photons with a finite correlation area and a turbulence model beyond the phase screen approximation are considered.

We study the scattering of magnetoinductive plane waves by internal (external) capacitive (inductive) defects coupled to a one-dimensional split-ring resonator array. We examine a number of simple defect configurations where Fano resonances occur and study the behavior of the transmission coefficient as a function of the controllable external parameters. We find that for embedded capacitive defects, the addition of a small amount of coupling to second neighbors is necessary for the occurrence of Fano resonance. For external inductive defects, Fano resonances are commonplace, and they can be tuned by changing the relative orientation or distance between the defect and the SSR array.

We predict the existence of a class of multidimensional light localizations in out-of-equilibrium ferroelectric crystals. In two dimensions, the nondiffracting beams form at an arbitrary low-power level and propagate even when their width is well below the optical wavelength. In three dimensions, a subwavelength light bullet is found. The effects emerge when compositionally disordered crystals are brought to their metastable glassy state, and leading to the suppression of evanescent waves, they can have a profound impact on super-resolved imaging and ultradense optical storage, resembling metamaterials in many ways.

We apply the input-output theory of optical cavities to formulate a quantum treatment of a continuous-wave singly resonant optical parametric oscillator. This case is mainly relevant to highly nondegenerate signal and idler modes. We show that both intensity and quadrature squeezing are present and that the maximum noise reduction below the standard quantum limit is the same at the signal and idler frequencies as in the doubly resonant case. As the threshold of oscillation is approached, however, the intensity-difference and quadrature spectra display a progressive line narrowing which is absent in the balanced doubly resonant case. By use of the separability criterion for continuous variables, the signal-idler state is found to be entangled over wide ranges of the parameters. We show that attainable levels of squeezing and entanglement make singly resonant configurations ideal candidates for two-color quantum information processes, because of their ease of tuning in experimental realizations.

In a numerical study, we demonstrate the dimensionality crossover in Anderson localization of light. We consider crossover from the two-dimensional (2D) to the one-dimensional (1D) lattice, optically induced in both linear and nonlinear dielectric media. The joint influence of nonlinearity and disorder on Anderson localization in such systems is discussed in some detail. We find that, in the linear regime, the localization is more pronounced in two dimensions than in one dimension. We also find that the localization in the intermediate cases of crossover is less pronounced than in both the pure 1D and 2D cases in the linear regime, whereas in the nonlinear regime this depends on the strength of the nonlinearity. There exist strongly nonlinear regimes in which 1D localization is more pronounced than the 2D localization, opposite to the case of the linear regime. We find that the dimensionality crossover is characterized by two different localization lengths, whose behavior is different along different transverse directions.

The second-order correlation function for light emitted from a strongly and near-resonantly driven dilute cloud of atoms is discussed. Because of the strong driving, the fluorescence spectrum separates into distinct peaks, for which the spectral properties can be defined individually. It is shown that the second-order correlations for various combinations of photons from different spectral lines exhibit bunching together with super-Poissonian or sub-Poissonian photon statistics, tunable by the choice of the detector positions. Additionally, a Cauchy-Schwarz inequality is violated for photons emitted from particular spectral bands. The emitted light intensity is proportional to the square of the number of particles, and thus can potentially be intense. Three different averaging procedures to model ensemble disorder are compared.

We report on the development of the theory of second-harmonic generation by an incoherent pump with broad angular and frequency spectra. We show that spatial as well as temporal walk-off effects in a nonlinear crystal result in angular dispersion of the second-harmonic radiation. We demonstrate that the acceptance angle in second-harmonic generation by incoherent light is caused by the width of the pump angular spectrum and the resulting angular dispersion of second-harmonic radiation but does not depend on crystal length. In this case the frequency spectrum of second-harmonic radiation is determined by its angular dispersion and the pump angular spectrum. The theory is supported by an experiment in which a LiIO${}_3$ crystal was pumped by a tungsten halogen lamp.

When an environmental disturbance to a quantum system has a wavelength much larger than the system size, all qubits in the system are under the action of the same error operator. The noiseless subsystem and decoherence-free subspace are immune to such collective noise. We construct simple quantum circuits that implement these error-avoiding codes for a small number $n$ of physical qubits. A single logical qubit is encoded with $n=3$ and 4, while two and three logical qubits are encoded with $n=5$ and 7, respectively. Recursive relations among subspaces employed in these codes play essential roles in our implementation.

In this work we describe how the window method, which has been used with ideal Kramers-Kroning (K-K) consistent dielectric functions, is affected by real optical data where some degree of K-K inconsistency is always present. Analysis using measured data of the frequency-dependent dielectric function for gold and phase-change materials shows that the window method can in some cases amplify the errors introduced in the calculation of the Casimir force due to K-K inconsistency instead of minimizing them. The latter indicates that caution is required for the proper choice of the window function for dielectric data analysis and Casmir force calculations.

A near-field phase singularity (NFPS) depending on the spin state of the incident electromagnetic (EM) radiation is very fascinating because it can enrich the functionality of the EM radiation in metamaterials. Here we present a microscopic dipole model to describe the NFPS effect under the time-harmonic quasistatic limit. The results reveal that NFPS exists for the longitudinal components of both electric and magnetic fields as well as the transverse component of time-averaged Poynting vector. The localized surface plasmon polariton in the subwavelength metallic structure contributes to enhance the generation efficiency of NFPS by introducing the resonance of the electric dipole. This effect not only is promising for microtrapping and manipulation but also enriches the functionality of the existing metamaterials.

In the framework of cavity QED, we propose a practical scheme to purify dynamically a bipartite entangled state using short chains of atoms coupled to high-finesse optical cavities. In contrast to conventional entanglement purification protocols, we avoid controlled-not gates, thus reducing complicated pulse sequences and superfluous qubit operations. Our interaction scheme works in a deterministic way and, together with entanglement distribution and swapping, opens a route toward efficient quantum repeaters for long-distance quantum communication.

We propose a measure of quantum efficiency of a multimode state of light that quantifies the amount of optical loss this state has experienced, and prove that this efficiency cannot increase in any linear-optical processing with destructive conditional measurements. Any loss that has affected a state can neither be removed nor redistributed so as to further increase the efficiency in higher-efficiency modes at the expense of lower-efficiency modes. This result eliminates the possibility of catalytically improving photon sources.

Quantum repeaters hold the promise to prevent the photon losses in communication channels. Most recently, the serious efforts have been applied to achieve scalable distribution of entanglement over long distances. However, the probabilistic nature of entanglement generation and realistic quantum memory storage times make the implementation of quantum repeaters an outstanding experimental challenge. We propose a quantum repeater protocol based on the deterministic storage of a single photon in atomic ensembles confined in distant high-finesse cavities and show that this system is capable of distributing the entanglement over long distances with a much higher rate as compared to previous protocols, thereby alleviating the limitations on the quantum memory lifetime by several orders of magnitude. Our scheme is robust with respect to phase fluctuations in the quantum channel, while the fidelity imperfection is fixed and negligibly small at each step of entanglement swapping.

We introduce the notion of the unextendible maximally entangled basis (UMEB), a set of orthonormal maximally entangled states in ${\mathbb{C}}^d\otimes {\mathbb{C}}^d$ consisting of fewer than $d^2$ vectors which have no additional maximally entangled vectors orthogonal to all of them. We prove that UMEBs do not exist for $d=2$ and give explicit constructions for a six-member UMEB with $d=3$ and a 12-member UMEB with $d=4$.

We calculate the Casimir interaction between two parallel wires and between a wire and a metal plate. The dielectric properties of the objects are described by the plasma, Drude, and perfect metal models. We find that at asymptotically large separation interactions involving plasma, wires and/or plates are independent of the material properties but depend on the dc conductivity $\sigma$ for Drude wires. Counterintuitively, at intermediate separations the interaction involving Drude wires can become independent of $\sigma$. At smaller separations, we compute the interaction numerically and observe an approach to the proximity approximation.

We investigate the Casimir force between a microfabricated elliptic cylinder (cylindrical lens) and a plate made of real materials. After a brief discussion of the fabrication procedure, which typically results in elliptic rather than circular cylinders, the Lifshitz-type formulas for the Casimir force and for its gradient are derived. In the specific case of equal semiaxes, the resulting formulas coincide with those derived previously for circular cylinders. The nanofabrication procedure may also result in asymmetric cylindrical lenses obtained from parts of two different cylinders, or rotated through some angle about the axis of the cylinder. In these cases, the Lifshitz-type formulas for the Casimir force between a lens and a plate and for its gradient are also derived, and the influence of lens asymmetry is determined. Additionally, we obtain an expression for the shift of the natural frequency of a micromachined oscillator with an attached elliptic cylindrical lens interacting with a plate via the Casimir force in a nonlinear regime.

Using first-principles calculations, we identify “tune-out” optical wavelengths, ${\lambda }_{\mathrm{zero}}$, for which the ground-state frequency-dependent polarizabilities of alkali-metal atoms vanish. Our approach uses high-precision, relativistic all-order method in which all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. We discuss the use of tune-out wavelengths for sympathetic cooling in two-species mixtures of alkali metals with group II and other elements of interest. Special cases in which these wavelengths coincide with strong resonance transitions in a target system are identified.

We report a study on light force on a beam of neutral two-level atoms superimposed upon a few-cycle-pulse Gaussian laser field under both resonant and off-resonant conditions. The phenomena of focusing, defocusing, and steering of the neutral atoms in the laser field are analyzed by solving the optical Bloch equation beyond the rotating-wave approximation and the force equation self-consistently. We find that two-level atoms in an atomic beam can be focused and defocused for large, positively and negatively detuned interactions even in the regime of extreme nonlinear optics. The so-called optical potential may be used for stable trapping of the neutral two-level atoms for large positively detuned interaction. This work successfully reproduces some of the features reported in recent experimental and theoretical works.

We propose a method for arbitrary manipulations of a quantum wave packet in an optical lattice by a suitable modulation of the lattice amplitude. A theoretical model allows us to determine the modulation needed to generate an arbitrary atomic trajectory; wave-packet rotations can also be implemented. The method is immediately usable in state-of-the-art experiments.