Tunable Topological Beam Splitter in Superconducting Circuit Lattice

In the usual Su–Schrieffer–Heeger (SSH) model with an even number of lattice sites, the topological pumping between left and right edge states cannot be easily realized since the edge states occupy two-end sites simultaneously. Here we propose a scheme to investigate the topological edge pumping in an even-sized periodically modulated SSH model mapped by a one dimensional superconducting transmission line resonators array. We find that the photon initially prepared in the first resonator can be finally observed at the two-end resonators with a certain proportion. The final photon splitting at the two-end resonators indicates that the present superconducting circuit is expected to realize the topological beam splitter. Further, we demonstrate that the splitting proportion between the two-end resonators can be arbitrarily tuned from 1 to 0, implying the potential feasibility of implementing the tunable topological beam splitter. Meanwhile, we also show that the tunable topological beam splitter is immune to the mild disorder added into the system due to the topology protection of the zero energy modes, and find that the tunable topological beam splitter is much more robust to the global on-site disorder compared with the nearest neighbor disorder. Our work greatly extends the practical application of topological matter in quantum information processing and opens up a new way towards the engineering of topological quantum optical device.

Lorentz Invariance Violation Tests in Astroparticle Physics

In this review, we present the latest exclusion limits obtained from astroparticles on Lorentz Invariance Violation (LIV) in the photon sector. We discuss the techniques known as energy-dependent time delay or time lag, subluminal pair production threshold shift, suppression of air shower formation, superluminal photon decay, and superluminal photon splitting. Perspectives for future results on LIV with the next generation of experiments are also addressed.

New constraints on Lorentz Invariance violation from Crab Nebula spectrum beyond 100 TeV

Recently two collaborations, Tibet and HAWC, presented new measurements of gamma-ray spectrum from Crab Nebula (Amenomori et al. in Phys Rev Lett 123(5):051101, 2019, arXiv:1906.05521 [astro-ph.HE]; Abeysekara et al. [HAWC Collaboration] in Astrophys. J. 881, 134, (2019), arXiv:1905.12518 [astro-ph.HE]) which continues beyond 100 TeV. We use these data to establish two-sided constraints on parameters of Lorentz Invariance violation in quantum electrodynamics. The limits on Lorentz violating mass scale for quartic dispersion relation are $$4.1\times 10^{14}\, \text{ GeV }$$4.1×1014GeV (photon splitting) and $$1.9\times 10^{13}\, \text{ GeV }$$1.9×1013GeV (photon decay) for superluminal case, and $$1.4\times 10^{12}$$1.4×1012 GeV (suppression of shower formation) for subluminal case.

Opacities for photon splitting and pair creation in neutron star magnetospheres

ABSTRACT Over the last four decades, persistent and flaring emission of magnetars observed by various telescopes has provided us with a suite of light curves and spectra in soft and hard X-rays, with no emission yet detected above around 1 MeV. Attenuation of such high-energy photons by magnetic pair creation and photon splitting is expected to be active in the magnetospheres of magnetars, possibly accounting for the paucity of gamma-rays in their signals. This paper explores polarization-dependent opacities for these two QED processes in static vacuum dipole magnetospheres of highly magnetized neutron stars, calculating attenuation lengths and determining escape energies, which are the maximum photon energies for transparency out to infinity. The numerical trajectory integral analysis in flat and curved space–times provides upper bounds of a few MeV or less to the visible energies for magnetars for locales proximate to the stellar surface. Photon splitting opacity alone puts constraints on the possible emission locales in their magnetospheres: regions within field loops of maximum altitudes $\, r_{{\rm max}}\sim 2\!-\!4\,$ stellar radii are not commensurate with maximum detected energies of around 250 keV. These constraints apply not only to magnetar flares but also to their quiescent hard X-ray tail emission. An exploration of photon splitting attenuation in the context of a resonant inverse Compton scattering model for the hard X-ray tails derives distinctive phase-resolved spectroscopic and polarimetric signatures, of significant interest for future MeV-band missions such as AMEGO and e-ASTROGAM.

Photon splitting bound on Lorentz Violation in QED from multi-TeV photon observation.

We calculate the width of photon splitting to three photons in a special model of quantum electrodynamics with broken Lorentz invariance. This process may lead to a sharp cut-off in a photon spectrum of a given astrophysical source. Analysing experimental data, we set a constraint on Lorentz-violating mass scale from the absence of such cut-off in the Crab Nebula spectrum.

Photon splitting in strongly magnetized medium with taking into account positronium influence

The process of the photon splitting, γ → γγ, is investigated in strongly magnetized vacuum with taking into account positronium influence. The dispersion properties of photons and the new polarization selection rules are obtained. The absorption rate of the leading photon splitting channels are calculated with taking account of the photon dispersion and wave function renormalization.

A Monte Carlo study of high-energy photon transport in matter: application for multiple scattering investigation in Compton spectroscopy

The first results of multiple scattering simulations of polarized high-energy X-rays for Compton experiments using a new Monte Carlo program,MUSCAT, are presented. The program is developed to follow the restrictions of real experimental geometries. The new simulation algorithm uses not only well known photon splitting and interaction forcing methods but it is also upgraded with the new propagation separation method and highly vectorized. In this paper, a detailed description of the new simulation algorithm is given. The code is verified by comparison with the previous experimental and simulation results by the ESRF group and new restricted geometry experiments carried out at SPring-8.

Photonic processes in Born–Infeld theory

We study the processes of photon–photon scattering and photon splitting in a magnetic field in Born–Infeld theory. In both cases we combine the terms from the tree-level Born–Infeld Lagrangian with the usual one-loop QED contributions, where those are approximated by the Euler–Heisenberg Lagrangian, including also the interference terms. For photon–photon scattering we obtain the total cross-section in the low-energy approximation. For photon splitting we compute the total absorption coefficient in the hexagon (weak field) approximation, and also show that, due to the non-birefringence property of Born–Infeld theory, the selection rules found by Adler for the QED case continue to hold in this more general setting. We discuss the bounds on the free parameter of Born–Infeld theory that may be obtained from this type of processes.