On September 14, 2015 at 09:50:45 UTC the two detectors of the Laser Interferometer Gravitational-Wave Observatory simultaneously observed a transient gravitational-wave signal. The signal sweeps upwards in frequency from 35 to 250 Hz with a peak gravitational-wave strain of 1.0 × 10 −21 . It matches the waveform predicted by general relativity for the inspiral and merger of a pair of black holes and the ringdown of the resulting single black hole. The signal was observed with a matched-filter signal-to-noise ratio of 24 and a false alarm rate estimated to be less than 1 event per 203 000 years, equivalent to a significance greater than 5.1σ. The source lies at a luminosity distance of 410 These observations demonstrate the existence of binary stellar-mass black hole systems. This is the first direct detection of gravitational waves and the first observation of a binary black hole merger.

We present an up-to-date, comprehensive summary of the rates for all types of compact binary coalescence sources detectable by the initial and advanced versions of the ground-based gravitational-wave detectors LIGO and Virgo. Astrophysical estimates for compact-binary coalescence rates depend on a number of assumptions and unknown model parameters and are still uncertain. The most confident among these estimates are the rate predictions for coalescing binary neutron stars which are based on extrapolations from observed binary pulsars in our galaxy. These yield a likely coalescence rate of 100 Myr−1 per Milky Way Equivalent Galaxy (MWEG), although the rate could plausibly range from 1 Myr−1 MWEG−1 to 1000 Myr−1 MWEG−1 (Kalogera et al 2004 Astrophys. J. 601 L179; Kalogera et al 2004 Astrophys. J. 614 L137 (erratum)). We convert coalescence rates into detection rates based on data from the LIGO S5 and Virgo VSR2 science runs and projected sensitivities for our advanced detectors. Using the detector sensitivities derived from these data, we find a likely detection rate of 0.02 per year for Initial LIGO–Virgo interferometers, with a plausible range between 2 × 10−4 and 0.2 per year. The likely binary neutron–star detection rate for the Advanced LIGO–Virgo network increases to 40 events per year, with a range between 0.4 and 400 per year.

Quasi-phase matching is a technique for phase matching nonlinear optical interactions in which the relative phase is corrected at regular intervals using a structural periodicity built into the nonlinear medium. The theory of quasiphase-matched second harmonic generation is presented in both the space domain and the wave vector mismatch domain. Departures from ideal quasi-phase matching in periodicity, wavelength, angle of propagation, and temperature are examined to determine the tuning properties and acceptance bandwidths for second harmonic generation in periodic structures. Numerical examples are tabulated for periodically poled lithium niobate. Various types of errors in the periodicity of these structures are then analyzed to find their effects on the conversion efficiency and on the shape of the tuning curve. This analysis is useful for establishing fabrication tolerances for practical quasi-phasematched devices. A method of designing structures having desired phase-matching tuning curve shapes is also described which makes use of varying domain lengths to establish a varying effective nonlinear coefficient along the interaction length.

Posting on personal website Yesanytime Yesno embargo No Posting on employer's or institution's website Yesat anytime Yes -12 month embargo No Posting on non-commercial institutional or subject repository Yesat anytime Yes -12 month embargo No

Nearly a century after Einstein first predicted the existence of gravitational waves, a global network of Earth-based gravitational wave observatories [1, 2, 3, 4] is seeking to directly detect this faint radiation using precision laser interferometry. Photon shot noise, due to the quantum nature of light, imposes a fundamental limit on the attometre-level sensitivity of the kilometre-scale Michelson interferometers deployed for this task. Here, we inject squeezed states to improve the performance of one of the detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) beyond the quantum noise limit, most notably in the frequency region down to 150 Hz, critically important for several astrophysical sources, with no deterioration of performance observed at any frequency. With the injection of squeezed states, this LIGO detector demonstrated the best broadband sensitivity to gravitational waves ever achieved, with important implications for observing the gravitational-wave Universe with unprecedented sensitivity

Unconventional, special-purpose machines may aid in accelerating the solution of some of the hardest problems in computing, such as large-scale combinatorial optimizations, by exploiting different operating mechanisms than those of standard digital computers. We present a scalable optical processor with electronic feedback that can be realized at large scale with room-temperature technology. Our prototype machine is able to find exact solutions of, or sample good approximate solutions to, a variety of hard instances of Ising problems with up to 100 spins and 10,000 spin-spin connections.

The gravitational-wave signal GW190521 is consistent with a binary black hole (BBH) merger source at redshift 0.8 with unusually high component masses, M e and M e , compared to previously reported

The cartoon of Fig. 1c illustrates a comparison of search mechanisms of the OPO network and classical and quantum annealing. Classical simulated annealing employs a downward vertical search, in which the temperature is repeatedly decreased and increased until the ground state is found. Quantum annealing exerts a horizontal search in the energy landscape with quantum tunnelling. Therefore, with these methods, the computational time of finding the ground state increases with the increase in the number of metastable excited states or local minima. In contrast, the OPO-based Ising machine searches for the ground state in an upward direction. The total energy, i.e. the ordinate in Fig.1c, is now replaced by the network loss. The ground state (optimum solution) has a minimum loss as shown in the figure. If we put a parametric gain (G) into such a network and increase it gradually, the first touch to the network loss happens at the ground state (L min ), which results in the single-mode oscillation of the ground state spin configuration. At the pump rate above this threshold point, the parametric gain is clamped at the same value of G = L min due to nonlinear gain saturation, so that all the other modes including local minima stay under the oscillation threshold. If we use the terminology of "negative temperature" to represent the parametric gain, the mentioned upward search corresponds to the heating process from T = −∞ for zero gain toward T = −0 for high gain. In this sense, the OPO machine is a "heating machine" while the classical simulated annealing is a "cooling machine." Theoretical Modelling and Numerical Test of OPO NetworkFemtosecond OPOs can be modelled by multimode analysis in the frequency domain as presented in [31]. Here for numerical simplicity, to simulate a network of N degenerate OPOs, we start with the quantum S-1