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Abstract: The long coherence time and high gate fidelities demonstrated using trapped ions have shown them to be excellent qubits for quantum computing. Increasing the number of ions on which high-fidelity two-qubit gates can be performed, however, is a significant obstacle to building a large-scale ion trap-based quantum information processor (QIP). The distributed quantum computation architecture solves this problem by linking small-scale QIPs to form a large-scale quantum computing network. Using photons as flying qubits is the natural choice for this link and enables any node-to-any-node interconnectivity. 
One process to establish inter-node entanglements is a probabilistic scheme. To establish entanglement between nodes, ions are initially entangled in different nodes with photons before performing a Bell state measurement on a pair of photons, which projects the two ions onto an entangled state. Traditionally this has been achieved using photons collected via spontaneous emission [1].
Alternatively, cavities may be employed to stimulate photon production via cavity-stimulated Raman transitions. Through this approach, a superior rate of photon collection can be achieved and control of both the temporal and spatial properties of the produced photons is possible.
Previous research within the group has demonstrated schemes that produce photons with greater indistinguishability, which are more robust against birefringence-induced decoherence. These improvements have been achieved through state selection and time-bin encoding, respectively [2,3].
The aim of this project is to build upon this research by producing Ion-photon entangled pairs.

[1] L. Stephenson et al., Phys. Rev. Lett., 124, 110501, (2020)
[2] T. Walker et al.,Phys. Rev. A, 102, 032616 (2020)
[3] T. Ward and M. Keller, New J. Phys., 24, 123028 (2022)

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Posted on behalf of: Department of Physics and Astronomy
Further information: Previous talks can be found at https://www.sussex.ac.uk/research/centres/sussex-centre-for-quantum-technologies/showcase/talks
Last updated: Friday, 26 April 2024