Topic
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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TL;DR: In this paper, the authors generalized the spin-flip superoperator to a universal inverter, which acts on quantum systems of arbitrary dimension and introduced the corresponding generalized concurrence for joint pure states of D-1 X D-2 bipartite quantum systems.
Abstract: Wootters [Phys. Rev. Lett. 80, 2245 (1998)] has given an explicit formula for the entanglement of formation of two qubits in terms of what he calls the concurrence of the joint density operator. Wootters's concurrence is defined with the help of the superoperator that flips the spin of a qubit. We generalize the spin-flip superoperator to a universal inverter, which acts on quantum systems of arbitrary dimension, and we introduce the corresponding generalized concurrence for joint pure states of D-1 X D-2 bipartite quantum systems. We call this generalized concurrence the I concurrence to emphasize its relation to the universal inverter. The universal inverter, which is a positive, but not completely positive superoperator, is closely related to the completely positive universal-NOT superoperator, the quantum analogue of a classical NOT gate. We present a physical realization of the universal-NOT Superoperator.
721 citations
TL;DR: In this paper, a quantum error correction code is proposed to protect a qubit of information against general one qubit errors, which can then be restored by a simple unitary transformation.
Abstract: We present a quantum error correction code which protects a qubit of information against general one qubit errors. To accomplish this, we encode the original state by distributing quantum information over five qubits, the minimal number required for this task. We describe a circuit which takes the initial state with four extra qubits in the state $|0〉$ to the encoded state. It can also be converted into a decoder by running it backward. The original state of the encoded qubit can then be restored by a simple unitary transformation.
716 citations
TL;DR: Density matrix tomography of the CROT gate shows that the gate fidelity achieved in the experiments is up to 0.9, good enough to be used in quantum algorithms.
Abstract: Rabi nutations of a single nuclear spin in a solid have been observed. The experiments were carried out on a single electron and a single 13C nuclear spin of a single nitrogen-vacancy defect center in diamond. The system was used for implementation of quantum logical NOT and a conditional two-qubit gate (CROT). Density matrix tomography of the CROT gate shows that the gate fidelity achieved in our experiments is up to 0.9, good enough to be used in quantum algorithms.
710 citations
TL;DR: This work demonstrates the creation of bipartite- and tripartite-entangled quantum states in a small quantum register consisting of individual 13C nuclei in a diamond lattice, which is adequate for sophisticated quantum operations.
Abstract: Robust entanglement at room temperature is a necessary requirement for practical applications in quantum technology. We demonstrate the creation of bipartite- and tripartite-entangled quantum states in a small quantum register consisting of individual 13C nuclei in a diamond lattice. Individual nuclear spins are controlled via their hyperfine coupling to a single electron at a nitrogen-vacancy defect center. Quantum correlations are of high quality and persist on a millisecond time scale even at room temperature, which is adequate for sophisticated quantum operations.
707 citations
TL;DR: In this article, the authors claimed electrical control of a quantum-dot charge qubit on a timescale orders of magnitude faster than previous measurements on electrically controlled charge- or spin-based qubits.
Abstract: Nature Communications 4: Article number: 1401 (2013); Published 29 January 2013; Updated 13 November 2013 In the original version of this Article, we claimed electrical control of a quantum-dot charge qubit on a timescale orders of magnitude faster than previous measurements on electrically controlled charge- or spin-based qubits.
705 citations