Group Seminar at MPQ: Multi-photon entangled states from a single atom

November 08, 2022

Philip Thomas, Quantum Dynamics Division MPQ
Group Seminar MPQ lecture hall and zoom
Tuesday, November 08th, 09:00am (MEZ)


A key challenge in the field of modern quantum science and technologies is to scale up the number of qubits while minimizing detrimental effects such as decoherence and crosstalk. Optical photons have the advantage that they interact weakly with the environment and thus naturally evade these issues. During the last decades many experiments on photonic entanglement were carried out using spontaneous parametric down conversion. However, the underlying process is intrinsically probabilistic and thus poses a practical limit on the size of entangled states one can generate. In order to avoid this obstacle, we use a single Rubidium atom in an optical cavity as an efficient photon source. Single photons are emitted sequentially while the atomic spin qubit mediates entanglement between them. We show that by tailored single-qubit operations on the atomic state we generate Greenberger-Horne-Zeilinger (GHZ) states of up to 14 photons and linear cluster states of up to 12 photons. A combined source-to-detection efficiency of 43% leads to coincidence rates orders of magnitude higher than the previous state-of-the-art. Our work represents a step towards scalable measurement-based quantum computing and communication.


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