title: Complete tomography of a high-fidelity solid-state entangled spin-photon qubit pair.
abstract: Entanglement between stationary quantum memories and photonic qubits is crucial for future quantum communication networks. Although high-fidelity spin-photon entanglement was demonstrated in well-isolated atomic and ionic systems, in the solid-state, where massively parallel, scalable networks are most realistically conceivable, entanglement fidelities are typically limited due to intrinsic environmental interactions. Distilling high-fidelity entangled pairs from lower-fidelity precursors can act as a remedy, but the required overhead scales unfavourably with the initial entanglement fidelity. With spin-photon entanglement as a crucial building block for entangling quantum network nodes, obtaining high-fidelity entangled pairs becomes imperative for practical realization of such networks. Here we report the first results of complete state tomography of a solid-state spin-photon-polarization-entangled qubit pair, using a single electron-charged indium arsenide quantum dot. We demonstrate record-high fidelity in the solid-state of well over 90%, and the first (99.9%-confidence) achievement of a fidelity that will unambiguously allow for entanglement distribution in solid-state quantum repeater networks.
authors.affiliation: E. L. Ginzton Laboratory, Stanford University, Stanford, California 94305, USA. kdegreve@stanford.edu
authors.forename: Kristiaan
authors.initials: K
authors.lastname: De Greve
authors.forename: Peter L
authors.initials: PL
authors.lastname: McMahon
authors.forename: Leo
authors.initials: L
authors.lastname: Yu
authors.forename: Jason S
authors.initials: JS
authors.lastname: Pelc
authors.forename: Cody
authors.initials: C
authors.lastname: Jones
authors.forename: Chandra M
authors.initials: CM
authors.lastname: Natarajan
authors.forename: Na Young
authors.initials: NY
authors.lastname: Kim
authors.forename: Eisuke
authors.initials: E
authors.lastname: Abe
authors.forename: Sebastian
authors.initials: S
authors.lastname: Maier
authors.forename: Christian
authors.initials: C
authors.lastname: Schneider
authors.forename: Martin
authors.initials: M
authors.lastname: Kamp
authors.forename: Sven
authors.initials: S
authors.lastname: Höfling
authors.forename: Robert H
authors.initials: RH
authors.lastname: Hadfield
authors.forename: Alfred
authors.initials: A
authors.lastname: Forchel
authors.forename: M M
authors.initials: MM
authors.lastname: Fejer
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Yamamoto