We report the first experimental demonstration of quantum entanglement among ten spatially separated single photons. A near-optimal entangled photon-pair source was developed with simultaneously a source brightness of ∼12  MHz/W, a collection efficiency of ∼70%, and an indistinguishability of ∼91% between independent photons, which was used for a step-by-step engineering of multiphoton entanglement. Under a pump power of 0.57 W, the ten-photon count rate was increased by about 2 orders of magnitude compared to previous experiments, while maintaining a state fidelity sufficiently high for proving the genuine ten-particle entanglement. Our work created a state-of-the-art platform for multiphoton experiments, and enabled technologies for challenging optical quantum information tasks, such as the realization of Shor's error correction code and high-efficiency scattershot boson sampling.

The Tile Calorimeter is the hadron calorimeter covering the central region of the ATLAS experiment at the Large Hadron Collider. Approximately 10,000 photomultipliers collect light from scintillating tiles acting as the active material sandwiched between slabs of steel absorber. This paper gives an overview of the calorimeter’s performance during the years 2008–2012 using cosmic-ray muon events and proton–proton collision data at centre-of-mass energies of 7 and 8 TeV with a total integrated luminosity of nearly 30 fb . The signal reconstruction methods, calibration systems as well as the detector operation status are presented. The energy and time calibration methods performed excellently, resulting in good stability of the calorimeter response under varying conditions during the LHC Run 1. Finally, the Tile Calorimeter response to isolated muons and hadrons as well as to jets from proton–proton collisions is presented. The results demonstrate excellent performance in accord with specifications mentioned in the Technical Design Report.

A search for doubly charged Higgs bosons with pairs of prompt, isolated, highly energetic leptons with the same electric charge is presented. The search uses a protonproton collision data sample at a centre-of-mass energy of 13 TeV corresponding to 36.1 fb −1 of integrated luminosity recorded in 2015 and 2016 by the ATLAS detector at the LHC. This analysis focuses on the decays H ±± → e ± e ± , H ±± → e ± μ ± and H ±± → μ ± μ ± , fitting the dilepton mass spectra in several exclusive signal regions. No significant evidence of a signal is observed and corresponding limits on the production cross-section and consequently a lower limit on m(H ±± ) are derived at 95% confidence level. With ± ± = e ± e ± /μ ± μ ± /e ± μ ± , the observed lower limit on the mass of a doubly charged Higgs boson only coupling to left-handed leptons varies from 770 to 870 GeV (850 GeV expected) for B(H ±± → ± ± ) = 100% and both the expected and observed mass limits are above 450 GeV for B(H ±± → ± ± ) = 10% and any combination of partial branching ratios. IntroductionEvents with two prompt, isolated, highly energetic leptons with the same electric charge (same-charge leptons) are produced very rarely in a proton-proton collision according to the predictions of the standard model (SM), but may occur with higher rate in various theories beyond the standard model (BSM). This analysis focuses on BSM theories that contain a doubly charged Higgs particle H ±± using the observed invariant mass of same-charge lepton pairs. In the absence of evidence for a signal, lower limits on the mass of the H ±± particle are set at the 95% confidence level.Doubly charged Higgs bosons can arise in a large variety of BSM theories, namely in left-right symmetric (LRS) e-mail: atlas.publications@cern.ch models [1][2][3][4][5], Higgs triplet models [6,7], the little Higgs model [8], type-II see-saw models [9][10][11][12][13], the GeorgiMachacek model [14], scalar singlet dark matter [15], and the Zee-Babu neutrino mass model [16][17][18]. Theoretical studies [19][20][21] [22]. Besides the leptonic decay, the H ±± particle can decay into a pair of W bosons as well. For low values of the Higgs triplet vacuum expectation value v , it decays almost exclusively to leptons while for high values of v the decay is mostly to a pair of W bosons [9,12]. In this analysis, the coupling to W bosons is assumed to be negligible and only pair production via the Drell-Yan process is considered. The Feynman diagram of the production mechanism is presented in Fig. 1.The analysis targets only decays of the H ±± particle into electrons and muons, denoted by . Other final states X that are not directly selected in this analysis are taken into account by reducing the lepton multiplicity of the final state. These states X would include, for instance, τ leptons or W bosons, as well as particles which escape detection. The total assumed branching ratio of H ±± is therefore B(Moreover, the decay width is assumed to be negligible compared to the detector resolution, which is compa...

Boson sampling is a problem strongly believed to be intractable for classical computers, but can be naturally solved on a specialized photonic quantum simulator. Here, we implement the first time-bin-encoded boson sampling using a highly indistinguishable (∼94%) single-photon source based on a single quantum-dot-micropillar device. The protocol requires only one single-photon source, two detectors, and a loop-based interferometer for an arbitrary number of photons. The single-photon pulse train is time-bin encoded and deterministically injected into an electrically programmable multimode network. The observed three- and four-photon boson sampling rates are 18.8 and 0.2 Hz, respectively, which are more than 100 times faster than previous experiments based on parametric down-conversion.

[1] In this paper, we studied the possible relations between incoming meteors, sporadic E (Es) layers, and sporadic (or sudden) sodium atom layers (SSLs) using the data from the FORMOSAT-3/COSMIC constellation, a meteor radar (Wuhan, 31°N, 114°E), and a sodium fluorescent lidar (Hefei, 31.8°N, 117.3°E). From a statistical point of view, a seasonal dependence of SSL correlates well with the annual variation of Es and is also consistent with seasonal meteor deposition except for February and March. It suggests that a "meteor-Es-SSL" chain could be reasonable if the recombination process were taken into consideration. Detailed study on the relationship between electron density profiles provided by the COSMIC radio occultation and the observations of SSLs by the University of Science and Technology of China via lidar illustrates that the appearance of Es accompanying SSL (i.e., 56.3%) is three times greater than that in the "normal" sodium layer. It also indicates that tides play an important role in causing the lower SSLs, which might be able to carry the upper dense electrons and ions in the Es layer formed by wind shear to the lower altitudes through downward phase propagations.