The total cross sections (TCSs) for $0.2–1000\mathrm{eV}$ positrons and for $0.8–1000\mathrm{eV}$ electrons colliding with ${\mathrm{SF}}_6$ molecules were measured by a relative method. In the present TCS investigation for electrons, peaks attributed to the $a_{1g}$, $t_{1g}$, $t_{2g}$, and $e_g$ shape resonances identified earlier were observed clearly at 2.2, 7.0, 12.5, and $30\mathrm{eV}$. In positron TCSs, a hump centered at about $2.6\mathrm{eV}$ was observed, followed by a larger and broader peak at around $50\mathrm{eV}$. These TCSs are compared with those for ${\mathrm{C}}_2{\mathrm{F}}_6$ molecules, a hexafluoro molecule showing roughly comparative structures at higher energies than $100\mathrm{eV}$, a feature that is attributable to the similarity in molecular size and polarizability. Especially for positron scattering, the TCSs are quite similar to each other over all the energy range investigated. Possible rationales for this similarity are provided.

We study Mott scattering in the presence of a strong elliptically polarized field. Using the first Born approximation and the Dirac–Volkov states for the electron, we obtain an analytic formula for the unpolarized differential cross section. This generalizes the results found for the linearly polarized field by Li et al. [ 67, 063409 (2003)] and for the circularly polarized field by Attaourti and Manaut [ 68, 067401 (2003)].

We present a simple method to generate controlled holes in the statistical distribution of quantized electromagnetic fields. This scheme extends previous approaches for the cavity field to a traveling one. It relies on combining a coherent state with a one-photon state, both impinging a single beam splitter plus a single detector.

In $2\otimes 2$, more than two orthogonal Bell states with a single copy can never be discriminated with certainty if only local operations and classical communication (LOCC) are allowed. We show here that more than $d$ numbers of pairwise orthogonal maximally entangled states in $d\otimes d$, which are in canonical form, used by Bennett et al. [Phys. Rev. Lett. 70, 1895 (1993)], can never be discriminated with certainty by LOCC, when single copies of the states are provided. Interestingly we show here that all orthogonal maximally entangled states, which are in canonical form, can be discriminated with certainty by LOCC if and only if two copies of each of the states are provided. We provide here a conjecture regarding the highly nontrivial problem of local distinguishability of any $d$ or fewer numbers of pairwise orthogonal maximally entangled states in $d\otimes d$ (in the single copy case).

We propose a method of improving the quality of a ring cavity that is imperfect due to nonunit mirror reflectivity. The method is based on using squeezed states of light pulses illuminating the mirror and gradual homodyne detection of radiation escaping from the cavity. Using measured data we can improve the state leaving the cavity by performing a single displacement and single squeezing operation. We discuss the contribution of this method to the process of storing unknown coherent and known squeezed states and the generation of squeezing in optical ring cavities.

Nonlocality without entanglement is an interesting field. A manifestation of quantum nonlocality without entanglement is the possible local indistinguishability of orthogonal product states. In this paper we analyze the character of operators to distinguish the elements of a full product basis set in a multipartite system, and show that distinguishing perfectly these product bases needs only local projective measurements and classical communication, and these measurements cannot damage each product basis. Employing these conclusions one can discuss local distinguishability of the elements of any full product basis set easily. Finally we discuss the generalization of these results to the locally distinguishability of the elements of incomplete product basis set.

We propose a scheme to generate an effective interaction of arbitrary strength between the internal degrees of freedom of two atoms placed in distant cavities connected by an optical fiber. The strength depends on the field intensity in the cavities. As an application of this interaction, we calculate the amount of entanglement it generates between the internal states of the distant atoms. The scheme effectively converts entanglement distribution networks to networks of interacting spins.

Both dipole and nondipole angular distribution parameters for photoelectrons emitted from the endohedral $\mathrm{Ne}@{\mathrm{C}}_{60}$ atom are investigated within both the framework of the Dirac bubble potential model and spherical, short range potential well of finite thickness $\Delta T$. It is demonstrated, for $1s$, $2s$, and $2p$ photoelectrons of $\mathrm{Ne}$, that because the fullerene shell acts as a resonator in this process, the energy dependence of the photoelectron angular distribution parameters differ considerably from that of the free $\mathrm{Ne}$ atom. For confined $\mathrm{Ne}$, in contrast to the isolated $\mathrm{Ne}$ atom, these parameters as a function of photon energy acquire a significant resonance structure, owing to oscillations in the photoionization matrix elements induced by the fullerene shell.

Non-Faraday rotation of photon-echo polarization was investigated at the $J=1\leftrightarrow J=0$ transition in a wide range of longitudinal magnetic field strength. The echo was generated at the intercombination transition $\left(6s6p\right){}^{3}P_1\to \left(6s^2\right){}^{1}S_0$ of ${}^{174}\mathrm{Yb}$ by two resonant laser pulses of linear (parallel or mutually orthogonal) polarization. A detailed analysis of the echo polarization performed by an angled echo technique has shown quite different behavior in the weak and strong magnetic field limits. The photon echo has polarization close to linear at a magnetic field strength $\mathcal{B}⩽5\mathrm{G}$; its polarization plane rotates around the magnetic field vector clockwise or counterclockwise depending on the magnetic field orientation relative to the wave vector. The photon-echo polarization components and echo power oscillate as functions of $\mathcal{B}$. As the magnetic field increases, the oscillations become smaller and almost disappear at a magnetic field $\mathcal{B}\approx 40\mathrm{G}$; the photon echo does not disappear at this magnetic field, but its polarization vector no longer has a preferred orientation. Numerical calculations of the photon echo generated at a spectral wide line agree with the experimental behavior of the photon-echo polarization for an arbitrary magnetic field.

This paper is concerned with the long-wavelength instabilities (infrared catastrophes) occurring in Bose-Einstein condensates (BECs). We examine the modulational instability in “cigar-shaped” (one-dimensional) attractive BECs and the transverse instability of dark solitons in “pancake” (two-dimensional) repulsive BECs. We suggest mechanisms, and give explicit estimates, on how to engineer the trapping conditions of the condensate to avoid such instabilities: the main result being that a tight enough trapping potential suppresses the instabilities present in the homogeneous limit. We compare the obtained estimates with numerical results and we highlight the relevant regimes of dynamical behavior.

We report an approach to bulk optical cooling of solid-state materials by placing the cooling medium inside a laser cavity. The laser system is a diode-pumped ${\mathrm{Yb}}^{3+}:\mathrm{K}\mathrm{Y}{\left(\mathrm{W}{\mathrm{O}}_4\right)}_2$ (KYW) laser, while the cooling medium is an uncoated sample of 2%-doped ${\mathrm{Yb}}^{3+}:\mathrm{Zr}{\mathrm{F}}_4\text{−}\mathrm{Ba}{\mathrm{F}}_2\text{−}\mathrm{La}{\mathrm{F}}_3\text{−}\mathrm{Al}{\mathrm{F}}_3\text{−}\mathrm{Na}\mathrm{F}$ (ZBLAN) glass. A typical drop of $6\mathrm{K}$ from ambient temperature was obtained from a noncontact temperature measurement based on the anti-Stokes luminescence profile, using diode pump power at the gain medium of $6\mathrm{W}$, a laser wavelength of $1027\mathrm{nm}$, and an absorbed power of $1.25\mathrm{W}$.

Considering $p$, $d$, and $f$ attachments to the $4f^{13}6s^2$ $J=\frac{7}{2}$ ground state of $\mathrm{Tm}\mathrm{I}$, we find no evidence for bound ${\mathrm{Tm}}^{-}$ states. A survey of possible weak attachments to excited $\mathrm{Tm}\mathrm{I}$ states, however, suggests three long lived states created by $6p$ attachment to the $4f^{12}5d6s^2$ $J=\frac{15}{2},\frac{17}{2}$ excited states. Calculated binding energies for these states are $254\mathrm{meV}$ for the $J=8$ state relative to its $4f^{12}5d6s^2$ $J=\frac{15}{2}$ threshold and 258 and $173\mathrm{meV}$ relative to the $J=\frac{17}{2}$ threshold for $J=9$ and $J=10$, respectively. These high $J$ $4f^{12}5d6s^{2}6p$ states have open decay channels only to $4f^{13}6s^2$ $J=\frac{7}{2},\frac{5}{2}$ and $4f^{12}5d6s^2$ $J=\frac{9}{2}$, resulting in emitted electrons of symmetry $ϵg$, $ϵh$, and $ϵi$. The lifetimes for these long lived $J=8,9,10$ states are estimated to be $9.8\mu \mathrm{s}$, $0.9\mathrm{ms}$, and $6.6\mathrm{ms}$, respectively.

The time-dependent variational principle in the stationary action principle form is formulated with constraint conditions for parametrized wave functions. The constraint conditions are classified into the first and the second classes as in Dirac’s constrained classical mechanics based on the commutability of operators. If the local bases in the parametrized wave functions construct a complete basis set, the classification of constraints with the commutator becomes equivalent to that with the complex generalized Poisson brackets (CGPB). However, in approximate wave functions with limited variational parameters, the equivalence between the CGPB and the commutator of operators is lost. The first-class constraints and the constants of motion classified with the commutator should be reconsidered as the pseudo-second-class constraints in the approximate wave functions.

Precise energies of rovibrational states of the exotic hydrogen-like molecule $\left(dt\mu \right)Xee$ are of importance for $dt\mu$ resonant formation, which is a key process in the muon-catalyzed fusion cycle. The effect of the internal structure and rotation of the $dt\mu$ quasi-nucleus on energy levels is studied using the three-body description of the $\left(dt\mu \right)Xee$ molecule based on the hierarchy of scales and corresponding energies of its constituent subsystems. For a number of rovibrational states of $\left(dt\mu \right)dee$ and $\left(dt\mu \right)tee$, the shifts and splittings of energy levels are calculated in the second order of the perturbation theory.

We report ellipsometric measurements made on semiconductor samples using photon-correlated beams produced by the process of spontaneous parametric down-conversion. Such a source yields higher accuracy than its quantum-limited conventional counterpart. We also show that our approach has the added advantage of not requiring an external reference sample for calibration.

Collisions between electrons and deprotonated mononucleotides, AMP and UMP, were studied at the electrostatic storage ring ELISA where the two anions were stored with a $1∕e$ lifetime of $13.5\mathrm{s}$. It is found that the threshold energy for electron-induced reactions leading to production of neutral fragments is as high as about $12\mathrm{eV}$ for both species. The high threshold is explained within the context of a classical reaction model, applicable for atomic anions, and a high electron-binding energy of about $5\mathrm{eV}$ for the two mononucleotides. There is no evidence in the cross sections for formation of short-lived doubly charged anions.

The radial equation of a simple potential model has long been known to yield an exponential survival law in a lowest-order (Breit-Wigner) approximation. We demonstrate that if the calculation is extended to fourth order, the survival law exhibits a parabolic short-time behavior which leads to the quantum Zeno effect. This model has further been studied numerically to characterize the extra exponential time parameter which compliments the lifetime. We also investigate the inverse Zeno effect.

We consider two different optimized measurement strategies for the discrimination of nonorthogonal quantum states. The first is ambiguous discrimination with a minimum probability of inferring an erroneous result, and the second is unambiguous, i.e., error-free, discrimination with a minimum probability of getting an inconclusive outcome, where the measurement fails to give a definite answer. For distinguishing between two mixed quantum states, we investigate the relation between the minimum-error probability achievable in ambiguous discrimination, and the minimum failure probability that can be reached in unambiguous discrimination of the same two states. The latter turns out to be at least twice as large as the former for any two given states. As an example, we treat the case where the state of the quantum system is known to be, with arbitrary prior probability, either a given pure state, or a uniform statistical mixture of any number of mutually orthogonal states. For this case we derive an analytical result for the minimum probability of error and perform a quantitative comparison with the minimum failure probability.

We compare and contrast the entanglement in the ground state of two Jahn-Teller models. The $E\otimes \beta$ system models the coupling of a two-level electronic system, or qubit, to a single-oscillator mode, while the $E\otimes \epsilon$ models the qubit coupled to two independent, degenerate oscillator modes. In the absence of a transverse magnetic field applied to the qubit, both systems exhibit a degenerate ground state. Whereas there always exists a completely separable ground state in the $E\otimes \beta$ system, the ground states of the $E\otimes \epsilon$ model always exhibit entanglement. For the $E\otimes \beta$ case we aim to clarify results from previous work, alluding to a link between the ground-state entanglement characteristics and a bifurcation of a fixed point in the classical analog. In the $E\otimes \epsilon$ case we make use of an ansatz for the ground state. We compare this ansatz to exact numerical calculations and use it to investigate how the entanglement is shared between the three system degrees of freedom.

Proofs from different theoretical frameworks, namely, the Hohenbergh–Kohn theorems, the Kohn–Sham scheme, and the first-order density matrix representation, have been presented in this paper to show that the functional derivative of the noninteracting kinetic energy density functional can uniquely be expressed as the negative of the Kohn–Sham effective potential, arbitrary only to an additive orbital-independent constant. Key points leading to the current result as well as confusion about the quantity in the literature are briefly discussed.