There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

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(-180)(+160)  Mpc corresponding to a redshift z=0.09(-0.04)(+0.03). In the source frame, the initial black hole masses are 36(-4)(+5)M⊙ and 29(-4)(+4)M⊙, and the final black hole mass is 62(-4)(+4)M⊙, with 3.0(-0.5)(+0.5)M⊙c(2) radiated in gravitational waves. All uncertainties define 90% credible intervals. 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.

/pdf/the-observation-of-gravitational-waves-from-a-binary-black-58srpupgg9.pdf

The Observation of Gravitational Waves from a Binary Black Hole Merger

From the Publisher: 
The accessible presentation of this book gives both a general view of the entire computer vision enterprise and also offers sufficient detail to be able to build useful applications. Users learn techniques that have proven to be useful by first-hand experience and a wide range of mathematical methods. A CD-ROM with every copy of the text contains source code for programming practice, color images, and illustrative movies. Comprehensive and up-to-date, this book includes essential topics that either reflect practical significance or are of theoretical importance. Topics are discussed in substantial and increasing depth. Application surveys describe numerous important application areas such as image based rendering and digital libraries. Many important algorithms broken down and illustrated in pseudo code. Appropriate for use by engineers as a comprehensive reference to the computer vision enterprise.

Computer vision : a modern approach = 计算机视觉 : 一种现代的方法

Researchers demonstrate the ability to multiplex and transfer data between twisted beams of light with different amounts of orbital angular momentum — a development that provides new opportunities for increasing the data capacity of free-space optical communications links.

/pdf/terabit-free-space-data-transmission-employing-orbital-47zsgn5cdx.pdf

Terabit free-space data transmission employing orbital angular momentum multiplexing

Quantum illumination (QI) is an entanglement-enhanced sensing system whose performance advantage over a comparable classical system survives its usage in an entanglement-breaking scenario plagued by loss and noise. In particular, QI's error-probability exponent for discriminating between equally likely hypotheses of target absence or presence is 6 dB higher than that of the optimum classical system using the same transmitted power. This performance advantage, however, presumes that the target return, when present, has known amplitude and phase, a situation that seldom occurs in light detection and ranging (lidar) applications. At lidar wavelengths, most target surfaces are sufficiently rough that their returns are speckled, i.e., they have Rayleigh-distributed amplitudes and uniformly distributed phases. QI's optical parametric amplifier receiver---which affords a 3 dB better-than-classical error-probability exponent for a return with known amplitude and phase---fails to offer any performance gain for Rayleigh-fading targets. We show that the sum-frequency generation receiver [Zhuang et al., Phys. Rev. Lett. 118, 040801 (2017)]---whose error-probability exponent for a nonfading target achieves QI's full 6 dB advantage over optimum classical operation---outperforms the classical system for Rayleigh-fading targets. In this case, QI's advantage is subexponential: its error probability is lower than the classical system's by a factor of $1/ln(M\overline{\ensuremath{\kappa}}{N}_{S}/{N}_{B})$, when $M\overline{\ensuremath{\kappa}}{N}_{S}/{N}_{B}\ensuremath{\gg}1$, with $M\ensuremath{\gg}1$ being the QI transmitter's time-bandwidth product, ${N}_{S}\ensuremath{\ll}1$ its brightness, $\overline{\ensuremath{\kappa}}$ the target return's average intensity, and ${N}_{B}$ the background light's brightness.

Quantum illumination for enhanced detection of Rayleigh-fading targets

The Internet is agog with stories about quantum radar. Will it really make stealth aircraft vulnerable? Were the microwave experiments reported in 2020 from Europe and Canada really proof-of-principle laboratory demonstrations of quantum radar’s advantage over classical radar? Or, does the 25 September 2020 news article in Science—entitled "The short, strange life of quantum radar"—paint the true picture? This paper disentangles microwave quantum radar’s alphabet soup: quantum illumination (QI) radar, quantum illumination with a microwave parametric amplifier receiver (QI-MPA) radar, quantum-correlated noise (QCN) radar, and quantum-correlated noise radar with a correlation receiver (QCN-CR). In particular, it evaluates—with no explicit quantum-mechanical notation or calculations—these radars’ miss probabilities at fixed false-alarm probability and it compares them to those for classical radar’s relevant alphabet soup, viz., coherent-state homodyne (CS-Hom) radar, coherent-state heterodyne (CS-Het) radar, classically-correlated noise (CCN) radar, and classically-correlated noise radar with a correlation receiver (CCN-CR). These comparisons show that, under ideal operating conditions, the QI and QI-MPA radars offer performance advantages over their best classical counterparts. Moreover, QI-MPA’s advantage is similar to that for its error-probability exponent when target absence and presence are equally likely and all radars make minimum error-probability decisions based on their respective measurements. Available theory, however, is unable to fully quantify QI’s advantage in the operating regime of interest. Ultimately—after accounting for problems that afflict QI and QI-MPA, but not their classical competitors, and factoring in realistic standoff-sensing parameters—it will be concluded that the aforementioned Science article has it correct. QI target detection has little to offer for standoff sensing, i.e., it does not compromise stealth aircraft.

Microwave Quantum Radar’s Alphabet Soup: QI, QI-MPA, QCN, QCN-CR

We describe a nonlinear processor, called the order-truncate-average-ratio spectral filter, that is designed to simultaneously whiten broadband background, preserve intermediate bandwidth features and suppress narrowband interference.

https://ieeexplore.ieee.org/iel4/5721/15310/00709078.pdf

On the performance of the order-truncate-average-ratio spectral filter

We observed evidence of spectral-phase-coherence in a singly-resonant biphoton frequency comb’s second-order cross-correlation function, and we verified the state’s time-energy entanglement by measuring Franson interference in 2 time-bins that violate the Bell inequality.

Mode-locked Phase Coherent Singly-Resonant Biphoton Frequency Comb

Quantum interference experiments based on coincidence counting are routinely employed -- for both diagnostic and application purposes -- on the signal and idler outputs of parametric downconverters. This paper uses the complete, Gaussian-state characterization of the downconversion process and quantum photodetection theory to provide an analytical framework for such measurements.

Jeffrey H. Shapiro

Papers

Quantum illumination for enhanced detection of Rayleigh-fading targets

Microwave Quantum Radar’s Alphabet Soup: QI, QI-MPA, QCN, QCN-CR

On the performance of the order-truncate-average-ratio spectral filter

Mode-locked Phase Coherent Singly-Resonant Biphoton Frequency Comb

Quantum Theory of Coincidence Counting: Gaussian States and Quantum Interference