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Publication# Emergence of highly coherent two-level systems in a noisy and dense quantum network

Abstract

Quantum sensors and qubits are usually two-level systems (TLS), the quantum analogues of classical bits assuming binary values 0 or 1. They are useful to the extent to which superpositions of 0 and 1 persist despite a noisy environment. The standard prescription to avoid decoherence of solid-state qubits is their isolation by means of extreme dilution in ultrapure materials. We demonstrate a different strategy using the rare-earth insulator LiY1-xTbxF4 (x = 0.001) which realizes a dense random network of TLS. Some TLS belong to strongly interacting Tb3+ pairs whose quantum states, thanks to localization effects, form highly coherent qubits with 100-fold longer coherence times than single ions. Our understanding of the underlying decoherence mechanisms-and of their suppression-suggests that coherence in networks of dipolar coupled TLS can be enhanced rather than reduced by the interactions.|Quantum coherence is hard to maintain in solid-state systems, as interactions usually lead to fast dephasing. Exploiting disorder effects and interactions, highly coherent two-level systems have now been realized in a rare-earth insulator compound.

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Ontological neighbourhood

Quantum computing

A quantum computer is a computer that exploits quantum mechanical phenomena. At small scales, physical matter exhibits properties of both particles and waves, and quantum computing leverages this behavior, specifically quantum superposition and entanglement, using specialized hardware that supports the preparation and manipulation of quantum states. Classical physics cannot explain the operation of these quantum devices, and a scalable quantum computer could perform some calculations exponentially faster than any modern "classical" computer.

Quantum information

Quantum information is the information of the state of a quantum system. It is the basic entity of study in quantum information theory, and can be manipulated using quantum information processing techniques. Quantum information refers to both the technical definition in terms of Von Neumann entropy and the general computational term. It is an interdisciplinary field that involves quantum mechanics, computer science, information theory, philosophy and cryptography among other fields.

Qubit

In quantum computing, a qubit (ˈkjuːbɪt) or quantum bit is a basic unit of quantum information—the quantum version of the classic binary bit physically realized with a two-state device. A qubit is a two-state (or two-level) quantum-mechanical system, one of the simplest quantum systems displaying the peculiarity of quantum mechanics. Examples include the spin of the electron in which the two levels can be taken as spin up and spin down; or the polarization of a single photon in which the two states can be taken to be the vertical polarization and the horizontal polarization.

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