Related topics: physical review letters

On the way to quantum networks

Physicists at LMU, together with colleagues at Saarland University, have successfully demonstrated the transport of an entangled state between an atom and a photon via an optic fiber over a distance of up to 20 km—thus ...

The mysterious movement of water molecules

Water is ubiquitous and essential for life. Nevertheless, experimental information about its behaviour on the atomic level—above all how it interacts with surfaces—is scarce. Thanks to a new experimental method, TU Graz ...

New method produces robust transistors

A new method to fit together layers of semiconductors as thin as a few nanometers has resulted in not only a scientific discovery but also a new type of transistor for high-power electronic devices. The result, published ...

Taking an X-ray of an atomic bond

Understanding the behavior of materials at their interfaces—where they connect to and interact with other materials—is central to engineering a variety of devices used to process, store and transfer information. Devices ...

Colliding molecules and antiparticles

Antiparticles—subatomic particles that have exactly opposite properties to those that make up everyday matter—may seem like a concept out of science fiction, but they are real, and the study of matter-antimatter interactions ...

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Perturbation theory (quantum mechanics)

In quantum mechanics, perturbation theory is a set of approximation schemes directly related to mathematical perturbation for describing a complicated quantum system in terms of a simpler one. The idea is to start with a simple system for which a mathematical solution is known, and add an additional "perturbing" Hamiltonian representing a weak disturbance to the system. If the disturbance is not too large, the various physical quantities associated with the perturbed system (e.g. its energy levels and eigenstates) can, from considerations of continuity, be expressed as 'corrections' to those of the simple system. These corrections, being 'small' compared to the size of the quantities themselves, can be calculated using approximate methods such as asymptotic series. We can therefore study the complicated system based on our knowledge of the simpler one.

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