Physicists create record-setting quantum motion

Showcasing precise control at the quantum level, physicists at the National Institute of Standards and Technology (NIST) have developed a method for making an ion (electrically charged atom) display exact quantities of quantum-level ...

Quantum interference in the service of information technology

Scientists from the Faculty of Physics, University of Warsaw, in collaboration with the University of Oxford and NIST, have shown that quantum interference enables processing of large sets of data faster and more accurately ...

The fun way to manipulate atoms

With their potential to perform calculations far beyond the reach of conventional supercomputers, machines harnessing certain quantum physics phenomena are expected to change the way the world solves complex problems. They ...

Limitation exposed in promising quantum computing material

Quantum computers promise to perform operations of great importance believed to be impossible for our technology today. Current computers process information via transistors carrying one of two units of information, either ...

Which is the perfect quantum theory?

For some phenomena in quantum many-body physics, several competing theories exist. But which of them describes a quantum phenomenon best? A team of researchers from the Technical University of Munich (TUM) and Harvard University ...

Researchers explore architectural design of quantum computers

A recent study led by Princeton University researchers, in collaboration with University of Maryland and IBM, explored the architectural design of quantum computers (QC). In a paper presented at the 2019 ACM/IEEE International ...

page 1 from 23

Quantum state

In quantum physics, a quantum state is a mathematical object that fully describes a quantum system. One typically imagines some experimental apparatus and procedure which "prepares" this quantum state; the mathematical object then reflects the setup of the apparatus. Quantum states can be statistically mixed, corresponding to an experiment involving a random change of the parameters. States obtained in this way are called mixed states, as opposed to pure states, which cannot be described as a mixture of others. When performing a certain measurement on a quantum state, the result generally described by a probability distribution, and the form that this distribution takes is completely determined by the quantum state and the observable describing the measurement. However, unlike in classical mechanics, the result of a measurement on even a pure quantum state is only determined probabilistically. This reflects a core difference between classical and quantum physics.

Mathematically, a pure quantum state is typically represented by a vector in a Hilbert space. In physics, bra-ket notation is often used to denote such vectors. Linear combinations (superpositions) of vectors can describe interference phenomena. Mixed quantum states are described by density matrices.

In a more general mathematical context, quantum states can be understood as positive normalized linear functionals on a C* algebra; see GNS construction.

This text uses material from Wikipedia, licensed under CC BY-SA