Quantum mechanics entails effects like superpositions and entanglement, which have no classical counterparts. From a technological standpoint these counterintuitive quantum aspects can be viewed as an unexploited resource that can be harnessed to support various tasks, e.g. in the domains of computation, communication, and metrology. In many applications, however, the potential of nonclassical states cannot practically be exploited due to detection inefficiencies. The authors address this limitation by experimentally realizing a novel detection scheme in which entangling interactions are time reversed. In this way, nonclassical many-particle states are disentangled, allowing them to be detected in a robust and technically feasible manner. In the context of quantum metrology, these nonlinear readout techniques extend the class of entangled probe states that can be leveraged for sensing applications without being limited by finite detector resolution. The authors present an active atom interferometer, where both the entangled state preparation and disentangling readout involve parametric amplification. This “SU(1,1)” interferometer is implemented with the help of spinor Bose–Einstein condensates, where amplification is implemented by atomic collisions leading to spin exchange.

This thesis presents a theoretical investigation into the creation and exploitation of quantum correlations and entanglement among ultracold atoms. Specifically, it focuses on these non-classical effects in two contexts: (i) tests of local realism with massive particles, e.g., violations of a Bell inequality and the EPR paradox, and (ii) realization of quantum technology by exploitation of entanglement, for example quantum-enhanced metrology. In particular, the work presented in this thesis emphasizes the possibility of demonstrating and characterizing entanglement in realistic experiments, beyond the simple “toy-models” often discussed in the literature. The importance and relevance of this thesis are reflected in a spate of recent publications regarding experimental demonstrations of the atomic Hong-Ou-Mandel effect, observation of EPR entanglement with massive particles and a demonstration of an atomic SU(1,1) interferometer. With a separate chapter on each of these systems, this thesis is at the forefront of current research in ultracold atomic physics.

Two clumps of matter pass through each other without sharing space; In some cases the colliding clumps of matter appear to deepen their distance even as they pass through each other. Clumps of a few hundred thousand lithium atoms that are cooled to within one-millionth of a degree above absolute zero a temperature so cold that the atoms march in lockstep and act as a single matter wave. The Interaction of light with matter has long been a field of interest for many quantum physicists, however, limited to the field of interaction plus the form of interaction. I've found it to be much better to look at not as a phenomenon but as something of a paradox, whether the audience find it tangible or not, this might probably be the best starting point if one wish to have million ways to see quantum theory in its entirety.

Quantum mechanics, the subfield of physics that describes the behavior of very small (quantum) particles, provides the basis for a new paradigm of computing. First proposed in the 1980s as a way to improve computational modeling of quantum systems, the field of quantum computing has recently garnered significant attention due to progress in building small-scale devices. However, significant technical advances will be required before a large-scale, practical quantum computer can be achieved. Quantum Computing: Progress and Prospects provides an introduction to the field, including the unique characteristics and constraints of the technology, and assesses the feasibility and implications of creating a functional quantum computer capable of addressing real-world problems. This report considers hardware and software requirements, quantum algorithms, drivers of advances in quantum computing and quantum devices, benchmarks associated with relevant use cases, the time and resources required, and how to assess the probability of success.

The counter-intuitive aspects of quantum physics have been long illustrated by thought experiments, from Einstein's photon box to Schrödinger's cat. These experiments have now become real, with single particles - electrons, atoms, or photons - directly unveiling the strange features of the quantum. State superpositions, entanglement and complementarity define a novel quantum logic which can be harnessed for information processing, raising great hopes for applications. This book describes a class of such thought experiments made real. Juggling with atoms and photons confined in cavities, ions or cold atoms in traps, is here an incentive to shed a new light on the basic concepts of quantum physics. Measurement processes and decoherence at the quantum-classical boundary are highlighted. This volume, which combines theory and experiments, will be of interest to students in quantum physics, teachers seeking illustrations for their lectures and new problem sets, researchers in quantum optics and quantum information.

In a technology driven civilization the quest for new and smarter materials is everlasting. They are required as platforms for developing new technologies or for improving an already existing technology. The discovery of a new material is no longer chance driven or accidental, but is based on careful reasoning structured by deep understanding of the microconstituents of materials - the atoms and molecules in isolation or in an assembly. That requires fair amount of exposure to quantum and statistical mechanics. `Understanding Properties of Atoms, Molecules and Materials' is an effort (perhaps the first ever) to bring all the necessary theoretical ingredients and relevant physical information in a single volume. The book introduces the readers (first year graduates) or researchers in material chemistry/engineering to elementary quantum mechanics of atoms, molecules and solids and then goes on to make them acquainted with methods of statistical mechanics (classical as well as quantum) along with elementary principles of classical MD simulation. The basic concepts are introduced with clarity and illustrated with easy to grasp examples, thus preparing the readers for an exploration through the world of materials - the exotic and the mundane. The emphasis has been on the phenomena and what shapes them at the fundamental level. A comprehensive description of modern designing principles for materials with examples is a unique feature of the book. The highlights of the book are comprehensive introduction and analysis of Quantum states of atoms and molecules The translational symmetry and quantum states in periodic and amorphous solids Band structure and tuning Classical and quantum statistics with applications to ideal gases (photons, phonons and electrons, molecules) Quantum states in type-I and type-II superconductors (elementary theory included) Magnetic materials, materials with GMR and CMR Shape memory effects in alloys and materials 2D materials (graphene and graphene analogus) NLO and photovoltaic materials Hydrogen storage material for mitigating the looming energy crisis Quantum states in low and high band gap semiconductors Semimetals Designer materials, etc. The volume is designed and organized to create interest in the science of materials and the silent revolution that is redefining the goals and boundaries of materials science continuously.

This book highlights time reversal acoustics, techniques based on the symmetry properties of acoustic fields. It has the unique feature that the first eleven chapters of the book are on the indepth studies of the theories of time reversal acoustics. The remaining chapters are on the four major applications of time reversal acoustics, together with their experimental setups and case studies: underwater communication, seismic exploration,nondestructive evaluation, and medical ultrasound imaging.. The gauge invariance approach to acoustic fields, proposed by the author in 2007, is confirmed by the successful fabrication of acoustical metamaterials and the applications of time reversal acoustics to superresolution. The book also presents groundbreaking applications of time reversal acoustics to underwater communication technology and the application of metamaterials to time reversal acoustics.