Emission of entangled photons by a dc-bias Josephson junction
When
Where
Event language(s)
Abstract:
We show experimentally that a purely dc biased Josephson junction in series with two microwave resonators emits entangled photons into the two resonators, which are then leaked into microwave transmission lines. The absence of a phase reference associated to the DC bias forbids using standard microwave techniques to assess the entanglement of the outgoing modes. To circumvent this difficulty, we compute second order coherence functions of the emitted photons to demonstrate the violation of an entanglement witness. The experimental results are found in quantitative agreement with theory, allowing us to identify the low frequency noise of the DC bias as the main limitation for the coherence time of the entangled modes. We also describe two additional technique of analysis of the experimental data without a stable pump: via the covariance matrix calculations and via the covariance in the frequency space. Finally, we describe entanglement of two microwave photons via an invisible low-frequency photon.