Nanocrystals store light energy and drive chemical reactions

Chemistry is increasingly making use of the trick plants can do with photosynthesis: driving chemical reactions that run poorly or do not occur spontaneously at all with light energy. This requires suitable photocatalysts ...

A new quantum component made from graphene

Less than 20 years ago, Konstantin Novoselov and Andre Geim first created two-dimensional crystals consisting of just one layer of carbon atoms. Known as graphene, this material has had quite a career since then.

How do neutrons interact with reactor materials?

Many applications rely on global theoretical models of how neutrons interact with nuclei over a wide range of incident neutron energies. These applications range from energy production to homeland security to medical treatments. ...

Trapping polaritons in an engineered quantum box

Australian researchers have engineered a quantum box for polaritons in a two-dimensional material, achieving large polariton densities and a partially "coherent" quantum state.

Physicists reach qubit computing breakthrough

Researchers from Arizona State University and Zhejiang University in China, along with two theorists from the United Kingdom, have been able to demonstrate for the first time that large numbers of quantum bits, or qubits, ...

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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.

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