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: High fidelity initialization of a single hole spin confined to a self-assembled quantum dot by optical pumping is demonstrated, demonstrating a negligible hole spin hyperfine interaction and suggesting a route to the realization of solid-state quantum networks that can intra-convert the spin state with the polarization of a photon.
Abstract: A quantum dot that can be optically initialized to contain a well-defined and very stable hole spin has been designed, with a relaxation time long enough to allow potential applications in solid-state quantum networks.
354 citations
TL;DR: By encoding the qubit into the decoherence-free subspace (DFS) of a pair of trapped 9Be+ ions, this work protects the qubits from environment-induced dephasing that limits the storage time of a qubit composed of a single ion.
Abstract: We demonstrate a decoherence-free quantum memory of one qubit. By encoding the qubit into the decoherence-free subspace (DFS) of a pair of trapped 9Be+ ions, we protect the qubit from environment-induced dephasing that limits the storage time of a qubit composed of a single ion. We measured the storage time under ambient conditions and under interaction with an engineered noisy environment and observed that encoding into the DFS increases the storage time by up to an order of magnitude. The encoding reversibly transfers an arbitrary qubit stored in a single ion to the DFS of two ions.
353 citations
TL;DR: It is conjecture that no explicit Trotter step of the electronic structure Hamiltonian is possible with fewer entangling gates, even with arbitrary connectivities, which represents significant practical improvements on the cost of mostTrotter-based algorithms for both variational and phase-estimation-based simulation of quantum chemistry.
Abstract: As physical implementations of quantum architectures emerge, it is increasingly important to consider the cost of algorithms for practical connectivities between qubits. We show that by using an arrangement of gates that we term the fermionic swap network, we can simulate a Trotter step of the electronic structure Hamiltonian in exactly N depth and with N^2/2 two-qubit entangling gates, and prepare arbitrary Slater determinants in at most N/2 depth, all assuming only a minimal, linearly connected architecture. We conjecture that no explicit Trotter step of the electronic structure Hamiltonian is possible with fewer entangling gates, even with arbitrary connectivities. These results represent significant practical improvements on the cost of most Trotter-based algorithms for both variational and phase-estimation-based simulation of quantum chemistry.
353 citations
TL;DR: In this paper, it was shown that the spin state of an electron localized to the nitrogen-vacancy centre can be transferred to the nuclear spin, where it can be stored until needed.
Abstract: A nitrogen impurity in diamond—where two of the carbon atoms are replaced by a nitrogen atom and a vacant lattice site—is seen as a valuable qubit. The spin of an electron localized to the nitrogen-vacancy centre is commonly used for processing. Researchers now show that this electron spin state can be transferred to the nitrogen nuclear spin, where it can be stored until needed.
352 citations
TL;DR: This work uses the electron spin of a nitrogen-vacancy centre in diamond to selectively initialize, control and read out carbon-13 spins in the surrounding spin bath and construct high-fidelity single- and two-qubit gates.
Abstract: Quantum registers of nuclear spins coupled to electron spins of individual solid-state defects are a promising platform for quantum information processing1,2,3,4,5,6,7,8,9,10,11,12,13. Pioneering experiments selected defects with favourably located nuclear spins with particularly strong hyperfine couplings4,5,6,7,8,9,10. To progress towards large-scale applications, larger and deterministically available nuclear registers are highly desirable. Here, we realize universal control over multi-qubit spin registers by harnessing abundant weakly coupled nuclear spins. We use the electron spin of a nitrogen–vacancy centre in diamond to selectively initialize, control and read out carbon-13 spins in the surrounding spin bath and construct high-fidelity single- and two-qubit gates. We exploit these new capabilities to implement a three-qubit quantum-error-correction protocol14,15,16,17 and demonstrate the robustness of the encoded state against applied errors. These results transform weakly coupled nuclear spins from a source of decoherence into a reliable resource, paving the way towards extended quantum networks and surface-code quantum computing based on multi-qubit nodes11,18,19. The electron spin of a nitrogen–vacancy centre in diamond can be used to initialize, control and read the surrounding nuclear spins.
352 citations