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Qubit

About: Qubit is a research topic. Over the lifetime, 29978 publications have been published within this topic receiving 723084 citations. The topic is also known as: quantum bit & qbit.


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Journal ArticleDOI
TL;DR: In this article, a highly symmetric and efficient scheme for the determination of a single qubit state, such as the polarization properties of photons emitted by a single-photon source, is presented.
Abstract: We present, and analyze thoroughly, a highly symmetric and efficient scheme for the determination of a single-qubit state, such as the polarization properties of photons emitted by a single-photon source. In our scheme there are only four measured probabilities, just enough for the determination of the three parameters that specify the qubit state, whereas the standard procedure would measure six probabilities.

193 citations

Journal ArticleDOI
TL;DR: In this paper, the authors implemented remote state preparation of a qubit from a hydrogen to a carbon nucleus in molecules of carbon-13 labeled chloroform 13 CHCl 3 over interatomic distances using liquid-state nuclear magnetic resonance techniques.

193 citations

Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate a phase gate of unprecedented speed on a nuclear spin qubit in a fullerene molecule, and use it to bang-bang decouple the qubit from a strong environmental interaction.
Abstract: Quantum mechanics permits an entity, such as an atom, to exist in a superposition of multiple states simultaneously Quantum information processing (QIP) harnesses this profound phenomenon to manipulate information in radically new ways1 A fundamental challenge in all QIP technologies is the corruption of superposition in a quantum bit (qubit) through interaction with its environment Quantum bang–bang control provides a solution by repeatedly applying ‘kicks’ to a qubit2, thus disrupting an environmental interaction However, the speed and precision required for the kick operations has presented an obstacle to experimental realization Here we demonstrate a phase gate of unprecedented speed3,4 on a nuclear spin qubit in a fullerene molecule, and use it to bang–bang decouple the qubit from a strong environmental interaction We can thus trap the qubit in closed cycles on the Bloch sphere, or lock it in a given state for an arbitrary period Our procedure uses operations on a second qubit, an electron spin, to generate an arbitrary phase on the nuclear qubit We anticipate that the approach will be important for QIP technologies, especially at the molecular scale where other strategies, such as electrode switching, are unfeasible

192 citations

Journal ArticleDOI
TL;DR: This work introduces a method to construct a set of frustrated Ising-model optimization problems with tunable hardness, and studies the performance of a D-Wave Two device with up to 503 qubits on these problems and compares it to a suite of classical algorithms.
Abstract: The availability of quantum annealing devices with hundreds of qubits has made the experimental demonstration of a quantum speedup for optimization problems a coveted, albeit elusive goal Going beyond earlier studies of random Ising problems, here we introduce a method to construct a set of frustrated Ising-model optimization problems with tunable hardness We study the performance of a D-Wave Two device (DW2) with up to 503 qubits on these problems and compare it to a suite of classical algorithms, including a highly optimized algorithm designed to compete directly with the DW2 The problems are generated around predetermined ground-state configurations, called planted solutions, which makes them particularly suitable for benchmarking purposes The problem set exhibits properties familiar from constraint satisfaction (SAT) problems, such as a peak in the typical hardness of the problems, determined by a tunable clause density parameter We bound the hardness regime where the DW2 device either does not or might exhibit a quantum speedup for our problem set While we do not find evidence for a speedup for the hardest and most frustrated problems in our problem set, we cannot rule out that a speedup might exist for some of the easier, less frustrated problems Our empirical findings pertain to the specific D-Wave processor and problem set we studied and leave open the possibility that future processors might exhibit a quantum speedup on the same problem set

192 citations

Journal ArticleDOI
TL;DR: It is shown that entanglement can always arise in the interaction of an arbitrarily large system in any mixed state with a single qubit in a pure state, and the time and temperature variation of a lower bound on the amount of entanglements produced is found.
Abstract: We show that entanglement can always arise in the interaction of an arbitrarily large system in any mixed state with a single qubit in a pure state. This small initial purity is enough to enforce entanglement even when the total entropy is close to maximum. We demonstrate this feature using the Jaynes-Cummings interaction of a two-level atom in a pure state with a field in a thermal state at an arbitrarily high temperature. We find the time and temperature variation of a lower bound on the amount of entanglement produced and study the classical correlations quantified by the mutual information.

192 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,977
20224,380
20213,014
20203,119
20192,594
20182,228