### New theory hints at more efficient way to develop quantum algorithms

In 2019, Google claimed it was the first to demonstrate a quantum computer performing a calculation beyond the abilities of today's most powerful supercomputers.

Related topics:
quantum information
· quantum computing
· quantum mechanics
· physical review letters
· quantum physics

In 2019, Google claimed it was the first to demonstrate a quantum computer performing a calculation beyond the abilities of today's most powerful supercomputers.

Quantum Physics

Aug 31, 2020

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If a tree falls in a forest and no one is there to hear it, does it make a sound? Perhaps not, some say.

Quantum Physics

Aug 24, 2020

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Traditional ways of producing entanglements, necessary for the development of any 'quantum internet' linking quantum computers, are not very well suited for fiber optic telecoms networks used by today's non-quantum internet. ...

Optics & Photonics

Aug 19, 2020

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Many quantum materials have been nearly impossible to simulate mathematically because the computing time required is too long. Now, a joint research group at Freie Universität Berlin and the Helmholtz-Zentrum Berlin (HZB, ...

Quantum Physics

Aug 17, 2020

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Physicists have long sought to understand the irreversibility of the surrounding world and have credited its emergence to the time-symmetric, fundamental laws of physics. According to quantum mechanics, the final irreversibility ...

Skoltech scientists have shown that quantum enhanced machine learning can be used on quantum (as opposed to classical) data, overcoming a significant slowdown common to these applications and opening a "fertile ground to ...

Quantum Physics

Jul 30, 2020

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Using a quantum computer to simulate time travel, researchers have demonstrated that, in the quantum realm, there is no "butterfly effect." In the research, information—qubits, or quantum bits—'time travel' into the simulated ...

Quantum Physics

Jul 29, 2020

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Quantum information is a field where the information is encoded into quantum states. Taking advantage of the "quantumness" of these states, scientists can perform more efficient computations and more secure cryptography compared ...

Quantum Physics

Jul 27, 2020

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Things can always be done faster, but can anything beat light? Computing with light instead of electricity is seen as a breakthrough to boost computer speeds. Transistors, the building blocks of data circuits, are required ...

Quantum Physics

Jul 20, 2020

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Electrons can interfere in the same manner as water, acoustical or light waves do. When exploited in solid-state materials, such effects promise novel functionality for electronic devices, in which elements such as interferometers, ...

Optics & Photonics

Jul 14, 2020

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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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