Business

Biden hails IBM's $20 bln investment announcement

IBM hosted US President Joe Biden Thursday to celebrate the announcement of a $20-billion investment in semiconductors, quantum computing and other cutting-edge technology in New York state.

Engineering

Tiny, cheap solution for quantum-secure encryption

It's fairly reasonable to assume that an encrypted email can't be seen by prying eyes. That's because in order to break through most of the encryption systems we use on a day-to-day basis, unless you are the intended recipient, ...

Computer Sciences

Observing time crystals on a quantum computer

When you hear the words "time crystal" you could be forgiven for imagining something fantastic like a magic crystal ball or a device for time travel. But time crystals are very real, although they are a bit like magic.

Engineering

Researchers discover novel quantum effect in bilayer graphene

Theorists at The University of Texas at Dallas, along with colleagues in Germany, have for the first time observed a rare phenomenon called the quantum anomalous Hall effect in a very simple material. Previous experiments ...

Computer Sciences

The first intuitive programming language for quantum computers

Programming quantum computers is becoming easier: computer scientists at ETH Zurich have designed the first programming language that can be used to program quantum computers as simply, reliably and safely as classical computers. ...

Hi Tech & Innovation

Project brings quantum internet closer to reality

A U.S. Army research result brings the quantum internet a step closer. Such an internet could offer the military security, sensing and timekeeping capabilities not possible with traditional networking approaches.

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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