Quantum Physics

Quantum mechanics
Quantum mechanics (wikipedia.org)

Quantum mechanics is a fundamental theory in physics that provides a description of the physical properties of nature at the scale of atoms and subatomic particles. It is the foundation of all quantum physics including quantum chemistry, quantum field theory, quantum technology, and quantum information science.

Classical physics, the description of physics that existed before the theory of relativity and quantum mechanics, describes many aspects of nature at an ordinary (macroscopic) scale, while quantum mechanics explains the aspects of nature at small (atomic and subatomic) scales, for which classical mechanics is insufficient. Most theories in classical physics can be derived from quantum mechanics as an approximation valid at large (macroscopic) scale.

Quantum mechanics differs from classical physics in that energy, momentum, angular momentum, and other quantities of a bound system are restricted to discrete values (quantization), objects have characteristics of both particles and waves (wave-particle duality), and there are limits to how accurately the value of a physical quantity can be predicted prior to its measurement, given a complete set of initial conditions (the uncertainty principle).

Quantum mechanics arose gradually from theories to explain observations which could not be reconciled with classical physics, such as Max Planck's solution in 1900 to the black-body radiation problem, and the correspondence between energy and frequency in Albert Einstein's 1905 paper which explained the photoelectric effect. These early attempts to understand microscopic phenomena, now known as the "old quantum theory", led to the full development of quantum mechanics in the mid-1920s by Niels Bohr, Erwin Schrödinger, Werner Heisenberg, Max Born and others. The modern theory is formulated in various specially developed mathematical formalisms. In one of them, a mathematical entity called the wave function provides information, in the form of probability amplitudes, about what measurements of a particle's energy, momentum, and other physical properties may yield.

Source: Quantum mechanics (wikipedia.org)

Muons: 'Strong' evidence found for a new force of nature

From sticking a magnet on a fridge door to throwing a ball into a basketball hoop, the forces of physics are at play in every moment of our lives. All of the forces we experience every day can be reduced to just four categories: gravity, electromagnetism, the strong force and the weak force.

An atomic marker hidden in plain sight

In the courtyard of a gift shop decorated with colourful ceramic frogs and dragonflies, it’s easy to overlook the historic marker. Perhaps that’s fitting for a secret site.

Tricking the perfect code machine

They don't often pose for goofy photographs - the members of the Quantum Hacking group at the Norwegian University of Science and Technology (NTNU), and the Centre for Quantum Technologies at the National University of Singapore. But everyone wants their picture taken with Eve.

Teleportation breakthrough made

Scientists have performed successful teleportation on atoms for the first time, the journal Nature reports. The feat was achieved by two teams of researchers working independently on the problem in the US and Austria.

Team's quantum object is biggest by factor of billions

Researchers have created a "quantum state" in the largest object yet. Such states, in which an object is effectively in two places at once, have until now only been accomplished with single particles, atoms and molecules.

Quantum trick for pressure-sensitive mobile devices

Hand-held devices could soon have pressure-sensitive touch-screens and keys, thanks to a UK firm's material that exploits a quantum physics trick. The technology allows, for example, scrolling down a long list or webpage faster as more pressure is applied.

Quantum physics explanation for smell gains traction

The theory that our sense of smell has its basis in quantum physics events is gaining traction, say researchers. The idea remains controversial, but scientists reporting at the American Physical Society meeting in Dallas, US, are slowly unpicking how it could work.

Quantum mechanics rule 'bent' in classic experiment

Researchers have bent one of the most basic rules of quantum mechanics, a counterintuitive branch of physics that deals with atomic-scale interactions. Its "complementarity" rule asserts that it is impossible to observe light behaving as both a wave and a particle, though it is strictly both.

Quantum computing: Is it possible, and should you care?

What is a quantum computer and when can I have one? It makes use of all that "spooky" quantum stuff and vastly increases computing power, right? And they'll be under every desk when scientists finally tame the spooky stuff, right? And computing will undergo a revolution no less profound than the one

Quantum computing device hints at powerful future

One of the most complex efforts toward a quantum computer has been shown off at the American Physical Society meeting in Dallas in the US. It uses the strange "quantum states" of matter to perform calculations in a way that, if scaled up, could vastly outperform conventional computers.

Majorana particle glimpsed in lab

Scientists think they may finally have seen evidence for a famously elusive quarry in particle physics. The Majorana fermion was first predicted 75 years ago - a particle that could be its own anti-particle.

Imaginary time

Imaginary time is a mathematical representation of time which appears in some approaches to special relativity and quantum mechanics. It finds uses in connecting quantum mechanics with statistical mechanics and in certain cosmological theories.

How long is a piece of string?

Alan Davies leaves behind his role in the TV quiz show QI to explore the world of quantum mechanics for the BBC science programme Horizon. The stand-up comic admits to deliberately failing at physics so he wouldn't have to take the O-level.

Higgs boson 'hints' also seen by US lab

The Higgs boson sub-atomic particle is a missing cornerstone in the accepted theory of particle physics. Researchers have been analysing data from the Tevatron machine near Chicago.

Free Will and Quantum Clones: How Your Choices Today Affect the Universe at its Origin

The late philosopher Robert Nozick, talking about the deep question of why there is something rather than nothing, quipped: "Someone who proposes a non-strange answer shows he didn't understand the question.

Antimatter Tevatron mystery gains ground

US particle physicists are inching closer to determining why the Universe exists in its current form, made overwhelmingly of matter. Physics suggests equal amounts of matter and antimatter should have been made in the Big Bang.

Quantum Leap: Information Teleported between Ions at a Distance

Quantum entanglement, whereby two or more objects are linked by an unseen connection, has some famously spooky effects. As quantum researcher Anton Zeilinger has said, entanglement can be thought of as a pair of dice that always land on the same number.

Physics of life: The dawn of quantum biology

The key to practical quantum computing and high-efficiency solar cells may lie in the messy green world outside the physics lab. On the face of it, quantum effects and living organisms seem to occupy utterly different realms.

Bridging the gap to quantum world

Scientists have "entangled" the motions of pairs of atoms for the first time. Entanglement is an effect in quantum mechanics, a relatively new branch of physics that is based more in probability than in classical laws.

Antihydrogen undergoes its first-ever measurement

The antimatter version of the hydrogen atom - antihydrogen - could soon finally give up its secrets. Scientists expect that antihydrogen will have exactly the same properties as hydrogen; but after 80 years, the test is only just becoming possible.

Neutrino 'ghost particle' sized up by astronomers

Scientists have made their most accurate measurement yet of the mass of a mysterious neutrino particle. Neutrinos are sometimes known as "ghost particles" because they interact so weakly with other forms of matter.

Neutrino particle 'flips to all flavours'

An important breakthrough may be imminent in the study of neutrinos. The multinational T2K project in Japan says it has seen indications in its data that these elementary particles can flip to any of their three types.

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