Quantum information science Quantum information science The Bell measurement is an important concept in quantum information science: It is a joint quantum-mechanical measurement of two qubits that determines in which of the four Bell states the two qubits are in. ...more on Wikipedia about "Bell measurement"
The Bell states are a concept in quantum information science and represent the simplest possible examples of entanglement. They are named after John S. Bell, as they are the subject of his famous Bell inequality. ...more on Wikipedia about "Bell state"
Bell's theorem is the most famous legacy of the late John Bell. It is famous for drawing an important line in the sand between quantum mechanics (QM) and the world as we know it intuitively. It is simple and elegant, and at the same time touches upon many of the fundamental philosophical issues that relate to modern physics. In its simplest form, Bell's theorem states: ...more on Wikipedia about "Bell's theorem"
BQP, in computational complexity theory, stands for " Bounded error, Quantum, Polynomial time". It denotes the class of problems solvable by a quantum computer in polynomial time, with an error probability of at most 1/4 for all instances. ...more on Wikipedia about "BQP"
In quantum computing, the cat state, named after Schrödinger's cat , is the special state where the qubits are in an equal superposition of all being |0> and all being |1>, i.e. |00...0> + |11...1>. ...more on Wikipedia about "Cat state"
A charge qubit is a superconducting qubit for quantum computing whose basis states are charge states (ie. states which represent the presence or absence of charge). A charge qubit is formed by a tiny superconducting island (also known as a Cooper-pair box) coupled by a Josephson junction to a superconducting reservoir (see figure). The state of the qubit is determined by the number of Cooper pairs which have tunneled across the junction. The charge qubit is typically read-out with an extremely sensitive electrometer such as the radio-frequency single-electron transistor. ...more on Wikipedia about "Charge qubit"
In quantum information science, classical information channel (often called simply classical channel) is a communication channel that can be used to transmit classical information (as opposed to quantum channel which can transmit quantum information). An example would be a light travelling over fiber optics lines or electricity travelling over phone lines. ...more on Wikipedia about "Classical information channel" I wish I had a www.shortopedia.com.
The Hadamard transform (Hadamard transformation, also known as the Walsh-Hadamard transformation) is an example of a generalized class of Fourier transforms. It is named for the French mathematician Jacques Hadamard. ...more on Wikipedia about "Hadamard transform"
The Kane quantum computer is a proposal for a scalable quantum computer proposed by Bruce Kane in 19981, then at the University of New South Wales. Often thought of as a hybrid between quantum dot and NMR quantum computers, the Kane computer is based on an array of individual phosphorus donor atoms embedded in a pure silicon lattice. Both the nuclear spins of the donors and the spins of the donor electrons participate in the computation. ...more on Wikipedia about "Kane quantum computer"
LOCC, or Local Operations and Classical Communication, is a method in quantum information theory where a local (product) operation is performed on part of the system, and where the result of that operation is "communicated" classically to another part where usually another local operation is performed. An example of this is distinguishing two Bell pairs, such as the following: ...more on Wikipedia about "LOCC"
The no cloning theorem is a result of quantum mechanics which forbids the creation of identical copies of an arbitrary unknown quantum state. It was stated by Wootters, Zurek, and Dieks in 1982, and has profound implications in quantum computing and related fields. ...more on Wikipedia about "No cloning theorem"
In quantum information theory, a no-communication theorem is a result which gives conditions under which instantaneous transfer of information between two observers is impossible. These results can be applied to understand the so-called paradoxes in quantum mechanics such as the EPR paradox or violations of local realism obtained in tests of Bell's theorem. In these experiments, the no-communication theorem shows that failure of local realism does not lead to what could be referred to as "spooky communication at a distance". ...more on Wikipedia about "No-communication theorem"
In functional analysis and quantum measurement theory, a POVM (Positive Operator Value Measure) is a measure whose values are non-negative self-adjoint operators on a Hilbert space. It is the most general formulation of a measurement in the theory of quantum physics. It arises from the fact that projective measurements on a larger system will act on subsystem in way that can not be described by projective measurement on the subsystem alone. They are frequently used in the field of Quantum information. POVM is to projective measurement what the density matrix is to the pure state. ...more on Wikipedia about "POVM"
Pure ensemble is one kind of system in quantum mechanics which is represented by identically prepared physical systems all characterized by the same ket. ...more on Wikipedia about "Pure ensemble"
A quantum channel is a communication channel which can transmit quantum information, as opposed classical information. An example of quantum information is the direction of the spin of an electron. An example of classical information is the text of this article, which has been transmitted classically over your internet connection. ...more on Wikipedia about "Quantum channel"
In quantum mechanics, a quantum circuit is a specific model for a quantum computational device. Experiments have already been carried out which can be regarded as implementing a seven-qubit quantum circuit that implements Shor's algorithm. Quantum circuits are also theoretically interesting as a tool for understanding the power and limitations of quantum computation. ...more on Wikipedia about "Quantum circuit"
A quantum computer is any device for computation that makes direct use of distinctively quantum mechanical phenomena, such as superposition and entanglement, to perform operations on data. In a classical (or conventional) computer, the amount of data is measured by bits; in a quantum computer, it is measured by qubits. The basic principle of quantum computation is that the quantum properties of particles can be used to represent and structure data, and that devised quantum mechanisms can be used to perform operations with this data. For a generally accessible overview of quantum computing, see Quantum Computing with Molecules , an article in Scientific American by Neil Gershenfeld and Isaac L. Chuang. ...more on Wikipedia about "Quantum computer"
Quantum cryptography is an approach to securing communications based on certain phenomena of quantum physics. Unlike traditional cryptography, which employs various mathematical techniques to restrict eavesdroppers from learning the contents of encrypted messages, quantum cryptography is focused on the physics of information. The process of sending and storing information is always carried out by physical means, for example photons in optical fibres or electrons in electric current. Eavesdropping can be viewed as measurements on a physical object — in this case the carrier of the information. What the eavesdropper can measure, and how, depends exclusively on the laws of physics. Using quantum phenomena such as quantum superpositions or quantum entanglement one can design and implement a communication system which can always detect eavesdropping. This is because measurements on the quantum carrier of information disturb it and so leave traces. ...more on Wikipedia about "Quantum cryptography"
In quantum mechanics quantum dense coding refers to a method of transmitting two bits of data using a single particle from an EPR pair. There exists a set of states accessible from an initial EPR state using one-particle operations that allows two bits to be reliably encoded in one spin-1/2 particle. ...more on Wikipedia about "Quantum dense coding"
Quantum entanglement is a quantum mechanical phenomenon in which the quantum states of two or more objects have to be described with reference to each other, even though the individual objects may be spatially separated. This leads to correlations between observable physical properties of the systems. For example, it is possible to prepare two particles in a single quantum state such that when one is observed to be spin-up, the other one will always be observed to be spin-down and vice versa, this despite the fact that it is impossible to predict, according to quantum mechanics, which set of measurements will be observed. As a result, measurements performed on one system seem to be instantaneously influencing other systems entangled with it. However, at this time classical information cannot be transmitted through entanglement faster than the speed of light. ...more on Wikipedia about "Quantum entanglement"
Quantum error correction techniques are methods to protect quantum information from errors due to decoherence and other noise. ...more on Wikipedia about "Quantum error correction"
A quantum gate or quantum logic gate is a rudimentary quantum circuit operating on a small number of qubits. They are the analogues for quantum computers to classical logic gates for conventional digital computers. Quantum logic gates are reversible, unlike many classical logic gates. Some universal classical logic gates, such as the Toffoli gate, provide reversibility and can be directly mapped onto quantum logic gates. Quantum logic gates are represented by unitary matrices. ...more on Wikipedia about "Quantum gate"
In quantum mechanics, quantum information is physical information that is held in the "state" of a quantum system. The most popular unit of quantum information is the qubit, a two-state quantum system. However, unlike classical digital states (which are discrete), a two-state quantum system can actually be in a superposition of the two states at any given time. ...more on Wikipedia about "Quantum information"
Quantum information science concerns information science that depends on quantum effects in physics. It includes theoretical issues in computational models as well as more experimental topics in quantum including what can and cannot be done with quantum information. The term quantum information theory is sometimes used, but it fails to encompass experimental research in the area. ...more on Wikipedia about "Quantum information science"
A quantum sort is any sort algorithm that runs on a quantum computer. Such an algorithm could at best be linearly faster than any existing sort algorithm (if based on comparisons like classical algorithms), but no such algorithm has actually been implemented. ...more on Wikipedia about "Quantum sort"
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