R. Bonifacio

Generation of XUV light by resonant frequency tripling in a two-wiggler FEL amplifier

Abstract FEL operation at short wavelengths is limited by electron-beam quality, by the availability of mirrors for oscillators and by the availability of input sources for FEL amplifiers. It is possible to use an FEL amplifier as a resonant-frequency tripling device, generating light and strong bunching at the third harmonic of a conventional input source in an initial wiggler section, then using a second wiggler section resonant at the tripled frequency to amplify the short-wavelength light. Neither mirrors nor a short-wavelength input source are required, and some relaxation of the electron-beam quality appears to be possible. We illustrate the scheme with a one-dimensional model and then with NUTMEG simulations of an 80 nm FEL amplifier initiated by a 240 nm input signal, in which an efficiency of the electron-beam power conversion to 80 nm light of nearly 10−4 was obtained.

Slippage and superradiance in the high-gain FEL: Linear theory

Abstract We describe the linear regime of a Free-Electron-Laser Amplifier taking into account propagation effects (slippage). We demonstrate analytically, (for a simple case) the existence of two different solutions of the pulse propagation equations, which in suitable limits describe the Steady-State and the Superradiant regimes.

Teleportation improvement by inconclusive photon subtraction

Inconclusive photon subtraction (IPS) is a conditional measurement scheme to force nonlinear evolution of a given state. In IPS the input state is mixed with the vacuum in a beam splitter and then the reflected beam is revealed by on-off photodetection. When the detector clicks we have the (inconclusive) photon subtracted state. We show that IPS on both channels of an entangled twin beam of radiation improves the fidelity of coherent state teleportation if the energy of the incoming twin beam is below a certain threshold, which depends on the beam splitter transmissivity and the quantum efficiency of photodetectors. We show that the energy threshold diverges when the transmissivity and the efficiency approach unity and compare our results with that of previous works on conclusive photon subtraction.

Collective atomic recoil laser (CARL) optical gain without inversion by collective atomic recoil and self-bunching of two-level atoms

Abstract We suggest a novel tunable laser concept, the Collective Atomic Recoil Laser (CARL) which unifies the physics of the FEL and of the atomic lasers. We demonstrate that a cold beam of two-level particles driven coherently by a counter-propagating resonant wave can amplify exponentially a co-propagating optical probe up to a saturation value through an instability very similar to that of a high gain FEL. In addition, the two level atoms undergo collective recoil and exponential self-bunching in space and form a longitudinal grating on the scale of the wavelength of the amplified optical signal.

Collective instability of a free electron laser including space charge and harmonics

Abstract The effects of harmonics, space charge and electron energy spread on the collective instability regime of an electron beam coupled to a planar undulator are analyzed. Both analytical and numerical results are presented.

Remote state preparation and teleportation in phase space

Continuous variable remote state preparation and teleportation are analysed using Wigner functions in phase space. We suggest a remote squeezed state preparation scheme between two parties sharing an entangled twin beam, where homodyne detection on one beam is used as a conditional source of squeezing for the other beam. The scheme also works with noisy measurements, and provides squeezing if the homodyne quantum efficiency is larger than 50%. The phase space approach is shown to provide a convenient framework to describe teleportation as a generalized conditional measurement, and to evaluate relevant degrading effects, such the finite amount of entanglement, the losses along the line and the nonunit quantum efficiency at the sender location.

Quantum effects in the collective light scattering by coherent atomic recoil in a Bose–Einstein condensate

We extend the semiclassical model of the collective atomic recoil laser (CARL) to include the quantum mechanical description of the center-of-mass motion of the atoms in a Bose-Einstein condensate (BEC). We show that when the average atomic momentum is less than the recoil momentum

Model-independent approach to nondissipative decoherence

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Hamiltonian model of a free electron laser

, the CARL equations reduce to the Maxwell-Bloch equations for two momentum levels. In the conservative regime (no radiation losses), the quantum model depends on a single collective parameter,

Quantum theory of SASE FEL

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