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Register a new userPhoton-photon interaction in structured QED vacuum
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Added by
Karen Hatsagortsyan
Publication date
2012
fields
Physics
and research's language is
English
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In spatially structured strong laser fields, quantum electrodynamical vacuum behaves like a nonlinear Kerr medium with modulated third-order susceptibility where new coherent nonlinear effects arise due to modulation. We consider the enhancement of vacuum polarization and magnetization via coherent spatial vacuum effects in the photon-photon interaction process during scattering of a probe laser beam on parallel focused laser beams. Both processes of elastic and inelastic four wave-mixing in structured QED vacuum accompanied with Bragg interference are investigated. The phase-matching conditions and coherent effects in the presence of Bragg grating are analyzed for photon-photon scattering.
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Quantum optical photodetection has occupied a central role in understanding radiation-matter interactions. It has also contributed to the development of atomic physics and quantum optics, including applications to metrology, spectroscopy, and quantum information processing. The quantum microwave regime, originally explored using cavities and atoms, is seeing a novel boost with the generation of nonclassical propagating fields in circuit quantum electrodynamics (QED). This promising field, involving potential developments in quantum information with microwave photons, suffers from the absence of photodetectors. Here, we design a metamaterial composed of discrete superconducting elements that implements a high-efficiency microwave photon detector. Our design consists of a microwave guide coupled to an array of metastable quantum circuits, whose internal states are irreversibly changed due to the absorption of photons. This proposal can be widely applied to different physical systems and can be generalized to implement a microwave photon counter.
We study how to search for photon-photon scattering in vacuum at present petawatt laser facilities such as HERCULES, and test Quantum Electrodynamics and non-standard models like Born-Infeld theory or scenarios involving minicharged particles or axion-like bosons. First, we compute the phase shift that is produced when an ultra-intense laser beam crosses a low power beam, in the case of arbitrary polarisations. This result is then used in order to design a complete test of all the parameters appearing in the low energy effective photonic Lagrangian. In fact, we propose a set of experiments that can be performed at HERCULES, eventually allowing either to detect photon-photon scattering as due to new physics, or to set new limits on the relevant parameters, improving by several orders of magnitude the current constraints obtained recently by PVLAS collaboration. We also describe a multi-cross optical mechanism that can further enhance the sensitivity, enabling HERCULES to detect photon-photon scattering even at a rate as small as that predicted by QED. Finally, we discuss how these results can be improved at future exawatt facilities such as ELI, thus providing a new class of precision tests of the Standard Model and beyond.
The analytical result for the six-photon helicity amplitudes in scalar QED is presented. To compute the loop, a recently developed method based on multiple cuts is used. The amplitudes for QED and $QED^{caln=1}$ are also derived using the supersymmetric decomposition linking the three theories.
In light-pulsed atom interferometry, the phase accumulated by atoms depends on the effective wave vector of the absorbed photons. In this work, we proposed a theory model to analyses the effective wave vector of photons in structured light. As for monochromatic optical field, a transverse confinement could lead to diffraction. We put forward that in light-atom interaction, the atom wave function could also provide a transverse confinement thus affect the effective wave vector of the absorbed photons. We calculated the relative shift of the photon effective wave vector when an atom with a Gaussian wave function absorbs one photon at the waist in a Gaussian beam. This shift could lead to a systematic effect related to atom spatial distribution in high precision experiment based on light-pulsed atom interferometry.
We revisit the information on the two lightest $a_0$ resonances and $S$-wave $pieta$ scattering that can be extracted from photon-photon scattering experiments. For this purpose we construct a model for the $S$-wave photon-photon amplitudes which satisfies analyticity properties, two-channel unitarity and obeys the soft photon as well as the soft pion constraints. The underlying I=1 hadronic $T$-matrix involves six phenomenological parameters and is able to account for two resonances below 1.5 GeV.We perform a combined fit of the $gammagammato pieta$ and $gammagammato K_SK_S$ high statistics experimental data from the Belle collaboration. Minimisation of the $chi^2$ is found to have two distinct solutions with approximately equal $chi^2$. One of these exhibits a light and narrow excited $a_0$ resonance analogous to the one found in the Belle analysis. This however requires a peculiar coincidence between the $J=0$ and $J=2$ resonance effects which is likely to be unphysical. In both solutions the $a_0(980)$ resonance appears as a pole on the second Riemann sheet. The location of this pole in the physical solution is determined to be $m-iGamma/2=1000.7^{+12.9}_{-0.7} -i,36.6^{+12.7}_{-2.6}$ MeV. The solutions are also compared to experimental data in the kinematical region of the decay $etatopi^0gammagamma$. In this region an isospin violating contribution associated with $pi^+pi^-$ rescattering must be added for which we provide a dispersive evaluation.
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