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Qbit
Qbit

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!!! Overview
qbit (qubit or [quantum] [bit]) is the basic unit of [quantum] information—the quantum version of the classical [binary] [bit] physically realized with a two-[state] [device]. [{$pagename}] is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics.
Examples include:
* the spin of the electron in which the two levels can be taken as spin up and spin down;
* the polarization of a single photon in which the two states can be taken to be the vertical polarization and the horizontal polarization.
[{$pagename}] can be in a coherent [superposition] of both [states]/levels simultaneously, where a classical system, a [bit] would have to be in one state or the other which is a property which is fundamental to [quantum] mechanics and quantum computing.!! [Bit] versus [{$pagename}]
A [binary] [digit], characterized as 0 and 1, is used to represent information in classical computers. A [binary] [digit] can represent up to one [bit] of [data entropy], where a [bit] is the basic unit of [data]. Typically the word [bit] is synonymous with [binary] [digit].
In classical [computer] technologies, a processed [bit] is implemented by one of two levels of low DC voltage, and switching from one of these two levels to the other, a so-called forbidden zone must be passed as fast as possible, as electrical voltage cannot change from one level to another instantaneously.
There are two possible outcomes for the measurement of a [qbit]—usually taken to have the value "0" and "1", like a [bit] or [binary] [digit]. However, whereas the [state] of a [bit] can only be either 0 or 1, the general [state] of a [qbit] according to [quantum] mechanics can be a [Coherence] [superposition] of both. The actual value is only known by measuring, which is [Observing|Observer], the value and determining the [Superposition] state.
[{$pagename}] state on measurement is the same as a [bit]. (0 or 1 or Up or Down)
Moreover, whereas a measurement of a classical [bit] would not disturb its [state], a measurement of a [qbit] would destroy its [coherence] and irrevocably disturb the [superposition] [state]. It is possible to fully encode one [bit] in one [qbit].However, a [qbit] can hold more information, e.g. up to two [bits] using superdense coding.
For a system of n components, a complete description of its [state] in classical physics requires only n [bits], whereas in quantum physics it requires 2n−1 complex numbers.
!! [{$pagename}]s and [Entanglement]
When you have two [Entangled|Entanglement] [{$pagename}], this implies that when you [Observe|Observer] the value of the first [{$pagename}] then you know the other is [{$pagename}]s value is known.
!! More Information
There might be more information for this subject on one of the following:
[{ReferringPagesPlugin before='*' after='\n' }]
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* [#1] - [Qubit|Wikipedia:Qubit|target='_blank'] - based on information obtained 2019-05-07
* [#2] - [p-bits for probabilistic spin logic|https://aip.scitation.org/doi/full/10.1063/1.5055860|target='_blank'] - based on information obtained 2019-05-07
This page (revision-1) was last changed on 29-Nov-2024 16:16 by UnknownAuthorTop