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arXiv:1905.08676 · Physical Review Letters

Entanglement between a Diamond Spin Qubit and a Photonic Time-Bin Qubit at Telecom Wavelength

Anna L. Tchebotareva, Sophie Hermans, Peter C. Humphreys, D. Voigt, Peter J. Harmsma, Lun K. Cheng, Ad L. Verlaan, Niels Dijkhuizen, Wim de Jong, A. Dréau, Ronald Hanson

Published Aug 5, 2019• 108 citations
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Abstract

We report on the realization and verification of quantum entanglement between a nitrogen-vacancy electron spin qubit and a telecom-band photonic qubit. First we generate entanglement between the spin qubit and a 637 nm photonic time-bin qubit, followed by photonic quantum frequency conversion that transfers the entanglement to a 1588 nm photon. We characterize the resulting state by correlation measurements in different bases and find a lower bound to the Bell state fidelity of ≥0.77±0.03. This result presents an important step towards extending quantum networks via optical fiber infrastructure.

DOI
10.1103/physrevlett.123.063601

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Efficient generation of entanglement between a stationary matter-qubit and a propagating photonic-qubit is a scientific and technological challenge of utmost importance for the realisation of fully-fledged quantum networks. Solid-state quantum emitters in the telecom C-band are a promising platform due to the minimal absorption of photons at these wavelengths and deterministic generation of high purity single photon flying qubits. Here, we use an InAs/InP quantum dot to implement an optically active spin-qubit and demonstrate high fidelity spin initialisation and coherent spin control of the resident electron. Lastly, for the first time we demonstrate high-fidelity spin-photon entanglement in a solid-state system with direct emission into the telecom C-band and obtain a lower bound on the entanglement fidelity of 80.07 %.
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