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Topic: Pure qubit state

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	Qubit - Quantiki
		That information is described by a state in a 2-level quantum mechanical system which is formally equivalent to a two-dimentional vector space over the complex numbers.
		A pure qubit state is a linear quantum superposition of those two states.
		A qubit's most important distinction from a classical bit, however, is not the continuous nature of the state (which can be replicated by any analog quantity), but the fact that multiple qubits can exhibit quantum entanglement.
	www.quantiki.org /wiki/index.php/Qubit (464 words)

	Pure qubit state: Definition and Links by Encyclopedian.com
		If the state 0⟩ is measured, a is...the state 0⟩ is measured, a is changed to a magnitude of 1 and b is changed to a magnitude...
		A pure qubit state is often written as the sum a 0⟩ + b 1⟩, or as a column vector (a, b) where a and b are the complex amplitudes associated with 0⟩ and 1⟩, respectively.
		If the state 0⟩ is measured, a is changed to a magnitude of 1 and b is changed to a magnitude of 0 (see magnitude of complex numbers).
	www.encyclopedian.com /pu/Pure-qubit-state.html (436 words)

	Qubit
		A qubit (quantum + bit; pronounced "Q-bit") is a two-state quantum system which is the smallest unit of quantum information.
		A pure qubit state is a linear quantum superposition of those two states.
		A number of qubits taken together is a qubit register[?].
	www.ebroadcast.com.au /lookup/encyclopedia/qu/Qubit.html (122 words)

	Qubit - Wikipedia, the free encyclopedia
		The states a qubit may be measured in are known as basis states (or vectors).
		A pure qubit state is a linear superposition of those two states.
		A number of entangled qubits taken together is a qubit register.
	en.wikipedia.org /wiki/Qubit (945 words)

	Realizing Qubits (Site not responding. Last check: )
		nucleus' state space is the same as that of a qubit, the precession implies that the state is not constant.
		3: Bloch sphere representation of a qubit state.
		For a pure state this vector is on the surface of the unit sphere, and for a mixed state, it is inside the unit sphere.
	www.eskimo.com /~knill/qip/nmrprhtml/node5.html (607 words)

	Pure qubit state
		Two pure qubit states are physically indistinguishable iff they are multiples of each other.
		Standard basis measurement is an operation in which information is gained about the state of the qubit.
		Strictly speaking, a measurement cannot be regarded as an operation on pure qubit states, since it transforms a pure state into a mixed state.
	www.danceage.com /biography/sdmc_Pure_qubit_state (187 words)

	Citebase - Optimal reconstruction of a pure qubit state with local measurements
		Citebase - Optimal reconstruction of a pure qubit state with local measurements
		Optimal reconstruction of a pure qubit state with local measurements
		Authors: Bagan, E. Baig, M. Monras, A. Munoz-Tapia, R. We analyse the reconstruction of an unknown pure qubit state.
	www.citebase.org /abstract?id=oai:arXiv.org:quant-ph/0312167 (190 words)

	Quantum state Summary
		A partially known quantum state, such as an ensemble with some quantum numbers fixed, can be described by a density operator.
		The simplest understanding of basis states is obtained by examining the quantum harmonic oscillator.
		A pure quantum state is a state which can be described by a single ket vector, or as a sum of basis states.
	www.bookrags.com /Quantum_state (1059 words)

	ACM Ubiquity - On the Realizability of Quantum Computers
		It is assumed that once the qubits, each placed into a superposition of 0 and 1 by the use of an appropriate rotation operator, are loaded individually on the n-cell register, Hamiltonians for the subsequent evolution of the set of n-qubits will somehow be found.
		One must remember that a pure state must yield a predictable outcome in a specified maximal test [8], and no such test may be conceptualized for the qubits on the quantum register in certain practical systems [9].
		Since the definition of a qubit includes arbitrary phase, it is necessary to consider errors from the perspective of the quantum state and not just from that of final measurement.
	www.acm.org /ubiquity/views/v7i11_quantumcomputers.html (2268 words)

	Quantum Information: Problem 3
		For two parties it is one less than the dimension of the smaller state space (a complete set of invariants is the set of Schmidt coefficients, which sum to 1 by normalisation).
		The number of invariants needed to uniquely specify a state up to local unitary transformations is not the same as the dimension D of the space of entanglement types; this is in general a curved space, with complicated geometry.
		For pure states of three qubits, which have D=6 (including the norm), a complete set of invariants [AAJT] consists of the six independent invariants given in [S] together with one more found by Grassl.
	www.imaph.tu-bs.de /qi/problems/3.html (1432 words)

	Some bipartite states do not arise from channels
		It is well known that the action of a quantum channel on a state can be represented, using an auxiliary space, as the partial trace of an associated bipartite state.
		Recently, it was observed that for the bipartite state associated with the optimal average input of the channel, the entanglement of formation is simply the entropy of the reduced density matrix minus the Holevo capacity.
		In [8], Wootters obtained an explicit formula for the EoF of a bipartite qubit state using a quantity designated as the concurrence.
	www.research.ibm.com /journal/rd/481/ruskai.html (1240 words)

	Citebase - Optimal scheme for estimating a pure qubit state via local measurements
		Optimal scheme for estimating a pure qubit state via local measurements
		Authors: Bagan, E. Baig, M. Munoz-Tapia, R. We present the optimal scheme for estimating a pure qubit state by means of local measurements on N identical copies.
		We give explicit examples for low N. For large N, we show that the fidelity saturates the collective measurement bound up to order 1/N. When the signal state lays on a meridian of the Bloch sphere, we show that this can be achieved without classical communication.
	www.citebase.org /abstract?id=oai:arXiv.org:quant-ph/0205026 (160 words)

	Mixtures and Density Operators (Site not responding. Last check: )
		The result is that the qubits are in a probabilistic ``mixture'' of two pure states.
		Except for measurement, the quantum gates that we have introduced so far are reversible and therefore transform pure states to pure states, so that no mixtures can be formed.
		The relationship between a qubit's state space and a sphere can be explained in terms of the qubit's density operators.
	www.eskimo.com /~knill/qip/prhtml/node9.html (529 words)

	CQC Intros: Quantum Computing
		These are further states, which in general have no classical analogues, in which the atom represents both values, 0 and 1, simultaneously.
		For example, if the qubits are atoms then suitably tuned laser pulses affect their electronic states and evolve initial superpositions of encoded numbers into different superpositions.
		When the physics of computation was first investigated systematically in the 1970s, the main fear was that quantum-mechanical effects might place fundamental bounds on the accuracy with which physical objects could realise the properties of bits, logic gates, the composition of operations, and so on, which appear in the abstract and mathematicallysophisticated theory of computation.
	www.physics.ohio-state.edu /~wilkins/writing/Assign/topics/qc.html (4214 words)

	CiteULike: Universal Measure of Entanglement (Site not responding. Last check: )
		Entanglement is defined as the difference in the correlation information encoded by the state of a system and a suitably defined separable state with the same marginals.
		The measure based on this decomposition is a generalization of the entanglement of formation to multipartite systems, provides an upper bound for the relative entropy of entanglement, and is directly computable on pure states.
		The example of pure three-qubit states is analyzed in detail, and a classification based on minimal, four-term decompositions is developed.
	www.citeulike.org /user/kevina/article/876403 (248 words)

	Quantum cobwebs: Universal entangling of quantum states (Site not responding. Last check: )
		Entangling an unknown qubit with one type of reference state is generally impossible.
		However, entangling an unknown qubit with two types of reference states is possible.
		Using shared-ZSA states, local operations and classical communication, we give a protocol for creating multipartite entangled states of an unknown quantum state with two types of reference states at remote places.
	www.ias.ac.in /pramana/v59/p221/abs.htm (131 words)

	Péter Lévay's Homepage
		Recently striking multiple relations have been found between pure state 2 and 3-qubit entanglement and extremal fl holes in string theory.
		In particular we show that finding the frozen values of the moduli in the calculation of the macroscopic entropy in the STU model, is related to finding the canonical form for a pure three-qubit entangled state defined by the dyonic charges.
		In this picture the extremization of the BPS mass with respect to moduli is connected to the problem of finding the optimal local distillation protocol of a GHZ state from an arbitrary pure three-qubit state.
	newton.phy.bme.hu /~levay/res2.html (175 words)

	Rinton Press - Publisher in Science and Technology
		Using a found representation for the GHZ states, it was shown that for dense coding schemes enhancement of the classical capacity of the channel due from entanglement is $N/N-1$.
		We find that in a pure state implementation of Grover's algorithm entanglement is present even though the initial and target states are product states.
		In pseudo-pure state implementations, the separability of the states involved defines an entanglement boundary in terms of a bound on the purity parameter.
	www.rintonpress.com /journals/qicabstracts/qicabstracts2-5.html (637 words)

	GIQ: Publications
		Bagan, M. Ballester, R. Muñoz-Tapia, O. Romero-Isart, Measuring the purity of a qubit state: entanglement estimation with fully separable measurements.
		Bagan, A. Monras, R. Muñoz-Tapia, Estimation of pure qubit states with collective and local measurements.
		Bagan, M. Baig, A. Monras, R. Muñoz-Tapia., Optimal reconstruction of a pure qubit state with local measurements.
	giq.ifae.es /publications.html (671 words)

	Pure Elegance (Site not responding. Last check: )
		Pure qubit state - In quantum information processing, a pure qubit state is a non-zero superposition of two basis states, conventionally written in bra-ket notation notation as
		Pure Prairie League (album) - Pure Prairie League is the self-titled debut album by American country rock band Pure Prairie League, released in 1972 (see 1972 in music).
		Formed in 2000 for Australia's Federation Centenary, it is the first purely ceremonial unit in the history of the Australian armed forces, and has since represented Australia in various roles both at home and around the world, including providing the guard at Buckingham Palace in...
	ne84.3rdfaze.info /pureelegance.html (1483 words)

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