All our former experience with application of quantum theory seems to say:
{\it what is predicted by quantum formalism must occur in laboratory} But the
essence of quantum formalism - entanglement, recognized by Einstein, Podolsky,
Rosen and Schr\"odinger - waited over 70 years to enter to laboratories as a
new resource as real as energy This holistic property of compound quantum systems, which involves
nonclassical correlations between subsystems, is a potential for many quantum
processes, including ``canonical'' ones: quantum cryptography, quantum
teleportation and dense coding However, it appeared that this new resource is
very complex and difficult to detect Being usually fragile to environment, it
is robust against conceptual and mathematical tools, the task of which is to
decipher its rich structure This article reviews basic aspects of entanglement including its
characterization, detection, distillation and quantifying In particular, the
authors discuss various manifestations of entanglement via Bell inequalities,
entropic inequalities, entanglement witnesses, quantum cryptography and point
out some interrelations They also discuss a basic role of entanglement in
quantum communication within distant labs paradigm and stress some
peculiarities such as irreversibility of entanglement manipulations including
its extremal form - bound entanglement phenomenon A basic role of entanglement
witnesses in detection of entanglement is emphasized

Quantum entanglement

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 statistical error in any estimation can be reduced by repeating the measurement and averaging the results. The central limit theorem implies that the reduction is proportional to the square root of the number of repetitions. Quantum metrology is the use of quantum techniques such as entanglement to yield higher statistical precision than purely classical approaches. In this Review, we analyse some of the most promising recent developments of this research field and point out some of the new experiments. We then look at one of the major new trends of the field: analyses of the effects of noise and experimental imperfections.

Advances in quantum metrology

Quantum mechanics, through the Heisenberg uncertainty principle, imposes limits on the precision of measurement. Conventional measurement techniques typically fail to reach these limits. Conventional bounds to the precision of measurements such as the shot noise limit or the standard quantum limit are not as fundamental as the Heisenberg limits and can be beaten using quantum strategies that employ “quantum tricks” such as squeezing and entanglement.

Quantum-enhanced measurements: beating the standard quantum limit.

The first quantum technology that harnesses quantum mechanical effects for its core operation has arrived in the form of commercially available quantum key distribution systems. This technology achieves enhanced security by encoding information in photons such that an eavesdropper in the system can be detected. Anticipated future quantum technologies include large-scale secure networks, enhanced measurement and lithography, and quantum information processors, which promise exponentially greater computational power for particular tasks. Photonics is destined to have a central role in such technologies owing to the high-speed transmission and outstanding low-noise properties of photons. These technologies may use single photons, quantum states of bright laser beams or both, and will undoubtedly apply and drive state-of-the-art developments in photonics.

Photonic quantum technologies

Summary form only given. It has been known for some time that entangled photon pairs, such as generated by spontaneous parametric down conversion, have unusual imaging characteristics with sub-shot-noise interferometric phase measurement. In fact, Fonseca, et al., recently demonstrated resolution of a two-slit diffraction patterned at half the Rayleigh limit in a coincidence counting experiment. What we show is that this type of effect is possible not only in coincidence counting experiments, but also in real two-photon absorbing systems, such as those used in classical interferometric lithography. In particular, we will demonstrate that quantum entanglement is the resource that allows sub-diffraction limited lithography.

/pdf/quantum-interferometric-lithography-exploiting-entanglement-shpquv5jfu.pdf

Quantum interferometric lithography: exploiting entanglement to beat the diffraction limit

Summary form only given. Roughly every eighteen months the number of transistors which fit on a micro-chip doubles. This has become to be known as Moore's Law. For years, this law has been correct, not in the least because the computer industry uses it as a production target. However, can this explosive increase in computing power be sustained in the future?. Computer manufacturers use optical lithography to print transistors on micro-chips. Since classical light cannot resolve features which are smaller than its wavelength, these transistors have a minimum size. It thus seems that the miniaturisation race does have to finish. However, this barrier turns out to be very much a classical barrier. The rules of nature all change when we exploit quantum effects. In collaboration with researchers from JPL in California we have developed a method called quantum lithography. It can be used to break through the miniaturisation barrier by using entangled photons. Currently, the method is still theoretical, but experimental progress is being made towards a full implementation of quantum lithography.

http://ieeexplore.ieee.org/iel5/7616/20763/00961864.pdf

Quantum lithography

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Reply: Jozsa et al.

Optical masking lithography has been the primary tool of the semiconductor industry for transferring circuit images onto substrates to form semiconductor chips.

Danial S. Abrams

Papers

Quantum interferometric lithography: exploiting entanglement to beat the diffraction limit

Quantum lithography

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Quantum Interferometric Optical Lithography: Exploiting Entanglement to Beat the Quantum Limit