Composite fermions and bosons: An invitation to electron masquerade in Quantum Hall

The two-dimensional electron gas formed at the semiconductor heterointerface is a theater for many intriguing plays of physics. The fractional quantum Hall effect (FQHE), which occurs in strong magnetic fields and low temperatures, is the most fascinating of them. The concept of composite fermions and bosons not only is beautiful by itself but also has proved highly successful in providing pictorial interpretation of the phenomena associated with the FQHE.

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Code for ‘Unbreakable’ Quantum Encryption Generated at Record Speed over Fiber

Raw code for “unbreakable” encryption, based on the principles of quantum physics, has been generated at record speed over optical fiber at the Commerce Department’s National Institute of Standards and Technology (NIST). The work, reported today at the SPIE Defense & Security Symposium in Orlando, Fla.,* is a step toward using conventional high-speed networks such as broadband Internet and local-area networks to transmit ultra-secure video for applications such as surveillance.

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Quantum Encryption as a Step Closer to Total Secrecy

The first computer network in the world protected by an “unbreakable” security system based on quantum encryption has been unveiled at a Viennese scientific conference.

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Team Sends Quantum Encryption 'Keys' Over Record Distances

Using an innovative sensor for detecting single photons, the smallest particles of light, scientists from Los Alamos National Laboratory (LANL), the National Institute of Standards and Technology (NIST) and Albion College (Albion, Mich.) have set two significant distance records for distributing "keys" (or codes) for quantum encryption, the most secure method known for protecting the privacy of information.

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Quantum attacks worry computer scientists

In the weird world of quantum computing, the state of computer systems networked together is so fragile that a read access to a single quantum bit, or qubit, on one machine would require a network-wide reset. It's no wonder, then, that two researchers who are working on ways of defending against the future possibility of malicious attack assume that any unauthorized access to a quantum computer constitutes a catastrophic failure.

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Quantum encryption and the weakness of European science

This week in Vienna, researchers demonstrated a working quantum key distribution (QKD) network, a feat that produced some good news and some bad news. The good news is that Siemens is probably going to be selling this stuff in a year or so; IT professionals, get ready to open your check books. On the other hand, by doing such a demo, the researchers show that QKD has passed from the realm of science into engineering, and they illustrate the weakness of fundamental scientific research in Europe.

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Quantum Encryption - An Introduction

“AT THE speed of light, Hephaestus’s sacred fire/ Blazed from beacon tower to beacon tower.” Thus, according to Aeschylus, spake Clytemnestra, an ancient queen of Mycenae, explaining how she received tidings that her husband Agamemnon was on his way home from the Trojan war. Perhaps Agamemnon would have done better to have turned up unannounced. The news left the queen and her lover just enough time to plot the cuckold’s assassination.

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Quantum Computer "Running"

Quantum computer solves problem, without running

By combining quantum computation and quantum interrogation, scientists at the University of Illinois at Urbana-Champaign have found an exotic way of determining an answer to an algorithm – without ever running the algorithm.

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What is a Quantum Computer?

Behold your computer. Your computer represents the culmination of years of technological advancements beginning with the early ideas of Charles Babbage (1791-1871) and eventual creation of the first computer by German engineer Konrad Zuse in 1941. Surprisingly however, the high speed modern computer sitting in front of you is fundamentally no different from its gargantuan 30 ton ancestors, which were equipped with some 18000 vacuum tubes and 500 miles of wiring! Although computers have become more compact and considerably faster in performing their task, the task remains the same: to manipulate and interpret an encoding of binary bits into a useful computational result. A bit is a fundamental unit of information, classically represented as a 0 or 1 in your digital computer. Each classical bit is physically realized through a macroscopic physical system, such as the magnetization on a hard disk or the charge on a capacitor. A document, for example, comprised of n-characters stored on the hard drive of a typical computer is accordingly described by a string of 8n zeros and ones. Herein lies a key difference between your classical computer and a quantum computer. Where a classical computer obeys the well understood laws of classical physics, a quantum computer is a device that harnesses physical phenomenon unique to quantum mechanics (especially quantum interference) to realize a fundamentally new mode of information processing.

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Quantum Time Waits for no Cosmos

THE INTRIGUING notion that time might run backwards when the Universe collapses has run into difficulties. Raymond Laflamme, of the Los Alamos National Laboratory in New Mexico, has carried out a new calculation which suggests that the Universe cannot start out uniform, go through a cycle of expansion and collapse, and end up in a uniform state. It could start out disordered, expand, and then collapse back into disorder. But, since the COBE data show that our Universe was born in a smooth and uniform state, this symmetric possibility cannot be applied to the real Universe.

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Quantum Mechanics for Beginners

Science is exciting because it is always in trouble. No matter how excellent a theory is, it always misses some point or other. Even our most precious ideas about the universe are not able to explain everything; there's always a blind spot. And when the hopeful folks zoom in on that blind spot it pretty much always turns out to be a lot larger than anybody thought, and all of us a mere bunch of naive beginners.

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What is Quantum Gravity?

Quantum gravity is the field of theoretical physics attempting to unify quantum mechanics, which describes three of the fundamental forces of nature (electromagnetism, weak interaction, and strong interaction), with general relativity, the theory of the fourth fundamental force: gravity. One ultimate goal hoped to emerge as a result of this is a unified framework for all fundamental forces— called a "theory of everything" (TOE).

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What is Quantum Field Theory?

In quantum field theory (QFT) the forces between particles are mediated by other particles. For instance, the electromagnetic force between two electrons is caused by an exchange of photons. But quantum field theory applies to all fundamental forces. Intermediate vector bosons mediate the weak force, gluons mediate the strong force, and gravitons mediate the gravitational force. These force carrying particles are virtual particles and, by definition, cannot be detected while carrying the force, because such detection will imply that the force is not being carried. In QFT photons are not thought of as 'little billiard balls', they are considered to be field quanta - necessarily chunked ripples in a field that 'look like' particles. Fermions, like the electron, can also be described as ripples in a field, where each kind of fermion has its own field. In summary, the classical visualisation of "everything is particles and fields", in quantum field theory, resolves into "everything is particles", which then resolves into "everything is fields". In the end, particles are regarded as excited states of a field (field quanta).

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What is Quantum Optics?

Quantum optics is a field of research in physics, dealing with the application of quantum mechanics to phenomena involving light and its interactions with matter.

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What is Quantum Mechanics?

Quantum mechanics is the study of mechanical systems whose dimensions are close to the atomic scale, such as molecules, atoms, electrons, protons and other subatomic particles. Quantum mechanics is a fundamental branch of physics with wide applications. Quantum theory generalizes classical mechanics to provide accurate descriptions for many previously unexplained phenomena such as black body radiation and stable electron orbits. The effects of quantum mechanics become evident at the atomic and subatomic level, and they are typically not observable on macroscopic scales. Superfluidity is one of the known exceptions to this rule.

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What is Quantum Electrodynamics?

Quantum electrodynamics (QED) is a relativistic quantum field theory of electrodynamics. QED was developed by a number of physicists, beginning in the late 1920s. It basically describes how light and matter interact. More specifically it deals with the interactions between electrons, positrons and photons. QED mathematically describes all phenomena involving electrically charged particles interacting by means of exchange of photons. It has been called "the jewel of physics" for its extremely accurate predictions of quantities like the anomalous magnetic moment of the electron, and the Lamb shift of the energy levels of hydrogen.

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