Observation of broadband entanglement in microwave radiation from the dynamical Casimir effect
Ben Schneider, Mr. Andreas Bengtsson, Ms. Ida-Maria Svensson, Thomas Aref, Prof. Göran Johansson, Dr. Jonas Bylander, Per Delsing
Received: 16th January 18
A fundamental property of the quantum vacuum is that a time-varying boundary condition for the electro-magnetic field can generate photons from the vacuum, the so-called the dynamical Casimir effect (DCE)1. The photons are created pairwise and should possess the particular quantum correlations referred to as entanglement.In particular, broadband entanglement sources are useful for two reasons: i) they can be very bright, generating a large number of entangled photons, and ii) the wide frequency content allows shaping the emitted radiation in time.Here we present the observation of entanglement generated in a broadband system using the DCE. The measured sample consists of a superconducting quantum interference device (SQUID) terminating a microwave transmission line. A magnetic flux modulates the SQUID's Josephson inductance at approximately 9~GHz, resulting in a time-varying boundary condition for the quantum vacuum in the transmission line. We detect both quadratures of the microwave radiation emitted at two different frequencies separated by 0.7~GHz.Analysing the measured data and using a careful calibration of the power level emitted from the sample, we determine the purity and type of entanglement using two different methods. We estimate an entanglement rate of 5~Mebit/s (mega entangled bits per second).
1 Gerald T. Moore. Quantum Theory of the Electromagnetic Field in a Variable‐Length One‐Dimensional Cavity. J. Math. Phys. , 11(9):2679–2691, 1970
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This is an abstract of a preprint hosted on an independent third party site. It has not been peer reviewed but is currently under consideration at Nature Communications.