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 $1.0 \times 10^{-21}$. 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 5.1 {\sigma}. The source lies at a luminosity distance of $410^{+160}_{-180}$ Mpc corresponding to a redshift $z = 0.09^{+0.03}_{-0.04}$. In the source frame, the initial black hole masses are $36^{+5}_{-4} M_\odot$ and $29^{+4}_{-4} M_\odot$, and the final black hole mass is $62^{+4}_{-4} M_\odot$, with $3.0^{+0.5}_{-0.5} M_\odot c^2$ 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.

https://physics.aps.org/featured-article-pdf/10.1103/PhysRevLett.116.061102

Observation of Gravitational Waves from a Binary Black Hole Merger

Quantum networks provide opportunities and challenges across a range of intellectual and technical frontiers, including quantum computation, communication and metrology. The realization of quantum networks composed of many nodes and channels requires new scientific capabilities for generating and characterizing quantum coherence and entanglement. Fundamental to this endeavour are quantum interconnects, which convert quantum states from one physical system to those of another in a reversible manner. Such quantum connectivity in networks can be achieved by the optical interactions of single photons and atoms, allowing the distribution of entanglement across the network and the teleportation of quantum states between nodes.

The quantum internet

Meeting the Universe Halfway is an ambitious book with far-reaching implications for numerous fields in the natural sciences, social sciences, and humanities. In this volume, Karen Barad, theoretical physicist and feminist theorist, elaborates her theory of agential realism. Offering an account of the world as a whole rather than as composed of separate natural and social realms, agential realism is at once a new epistemology, ontology, and ethics. The starting point for Barad’s analysis is the philosophical framework of quantum physicist Niels Bohr. Barad extends and partially revises Bohr’s philosophical views in light of current scholarship in physics, science studies, and the philosophy of science as well as feminist, poststructuralist, and other critical social theories. In the process, she significantly reworks understandings of space, time, matter, causality, agency, subjectivity, and objectivity.

In an agential realist account, the world is made of entanglements of “social” and “natural” agencies, where the distinction between the two emerges out of specific intra-actions. Intra-activity is an inexhaustible dynamism that configures and reconfigures relations of space-time-matter. In explaining intra-activity, Barad reveals questions about how nature and culture interact and change over time to be fundamentally misguided. And she reframes understanding of the nature of scientific and political practices and their “interrelationship.” Thus she pays particular attention to the responsible practice of science, and she emphasizes changes in the understanding of political practices, critically reworking Judith Butler’s influential theory of performativity. Finally, Barad uses agential realism to produce a new interpretation of quantum physics, demonstrating that agential realism is more than a means of reflecting on science; it can be used to actually do science.

Meeting the Universe Halfway: Quantum Physics and the Entanglement of Matter and Meaning

The paper gives a survey on recent experiments on the deterministic generation of photons. Experiments using Rydberg atoms in microwave cavities and trapped ions in optical cavities are discussed. The latter experiments show that lasers on the basis of single atoms are possible.

Generation of photons on demand using cavity quantum electrodynamics

The alkali atoms are especially attractive for the investigation of multi-photon processes. The ionization potentials are small so that the energy of only a few visible photons is sufficient to ionize the atoms. Therefore, dye lasers can be used for the experiments and, in particular, make it possible to investigate, among other things, the wavelength dependence of the photoionization cross sections. On the other hand, the simplicity of the alkali energy level scheme is an advantage for the theoretical understanding and interpretation of the results.

Multiphoton Ionization of Atoms

We present a detailed, (hopefully) pedagogical, analysis of amplitude and intensity correlations from two two-level atoms. We discuss various schemes to examine interference in scattering from two two-level systems, both with semiclassical treatment and quantum mechanical treatment. We show realization of quantum eraser and subensemble sorting in two different schemes of two two-level systems. We also show how the two-photon correlation can be useful in quantum imaging.

http://iopscience.iop.org/article/10.1088/0953-4075/38/9/005/pdf

A simple study of photon correlations from Hanbury-Brown and Twiss to Einstein, Podolsky, Rosen and beyond

The widely discussed applications in quantum information and quantum cryptography require radiation sources capable of producing a fixed number of photons. This paper reviews the work performed in our laboratory using the one-atom maser or micromaser to produce these fields on demand. In order to achieve this goal the maser is operating under the condition of the so-called trapping states. In this situation the field of the micromaser stabilises to a photon number state. In the second part of the paper a single photon source on the basis of a trapped ion will be described. The strong localization and position control available when an ion trap is combined with an optical cavity is a big step forward in producing a deterministic atom-field coupling necessary for quantum information processing.

Quantum optics of single atoms

A Quantum Monte Carlo wave function approach is used to rule out the possibility of cooperative effects in the quantum jump statistics of adjacent three-level ions of the type discussed in a series of experiments and theoretical investigations. By deriving analytical results and examining quantum jumps in various subspaces, we track this outcome to the fact that a fast spontaneous decay inhibits dipole-dipole-induced entanglement between the ions developing on a much slower time scale. This inhibition is demonstrated even for weak pumping of the fast transition. The Quantum Monte Carlo calculation thus sheds new light on the controversy arising from the findings of two recent conflicting experiments by Block et al. (Eur. Phys. J. D, 7 (1999) 461) and Donald et al. (Europhys. Lett., 51 (2000) 388).

/pdf/inhibition-of-cooperative-quantum-jumps-due-to-fast-33mzdtxngz.pdf

Herbert Walther

Papers

Generation of photons on demand using cavity quantum electrodynamics

Multiphoton Ionization of Atoms

A simple study of photon correlations from Hanbury-Brown and Twiss to Einstein, Podolsky, Rosen and beyond

Quantum optics of single atoms

Inhibition of cooperative quantum jumps due to fast spontaneous decay