article published Christopher Eichler author Deniz Bozyigit author C Lang author Matthias Baur author L. Steffen author Johannes M Fink author 4B591CBA-F248-11E8-B48F-1D18A9856A870000-0001-8112-028X Stefan Filipp author Andreas Wallraff author Continuous variable entanglement between two modes of a radiation field is usually studied at optical frequencies. Here we demonstrate experiments that show the entanglement between microwave photons of different energy in a broadband squeezed beam. We use a Josephson parametric amplifier to generate the two-mode correlated state and detect all four quadrature components simultaneously in a two-channel heterodyne setup using amplitude detectors. Analyzing two-dimensional phase space histograms for all possible pairs of quadratures allows us to determine the full covariance matrix, which is in good agreement with the one expected for a two-mode squeezed state. American Physical Society2011 10.1103/PhysRevLett.107.113601 10711 yes Eichler C, Bozyigit D, Lang C, et al. Observation of two-mode squeezing in the microwave frequency domain. <i>Physical Review Letters</i>. 2011;107(11). doi:<a href="https://doi.org/10.1103/PhysRevLett.107.113601">10.1103/PhysRevLett.107.113601</a> Eichler C, Bozyigit D, Lang C, Baur M, Steffen L, Fink JM, Filipp S, Wallraff A. 2011. Observation of two-mode squeezing in the microwave frequency domain. Physical Review Letters. 107(11). C. Eichler <i>et al.</i>, “Observation of two-mode squeezing in the microwave frequency domain,” <i>Physical Review Letters</i>, vol. 107, no. 11. American Physical Society, 2011. Eichler, C., Bozyigit, D., Lang, C., Baur, M., Steffen, L., Fink, J. M., … Wallraff, A. (2011). Observation of two-mode squeezing in the microwave frequency domain. <i>Physical Review Letters</i>. American Physical Society. <a href="https://doi.org/10.1103/PhysRevLett.107.113601">https://doi.org/10.1103/PhysRevLett.107.113601</a> Eichler, Christopher, Deniz Bozyigit, C Lang, Matthias Baur, L. Steffen, Johannes M Fink, Stefan Filipp, and Andreas Wallraff. “Observation of Two-Mode Squeezing in the Microwave Frequency Domain.” <i>Physical Review Letters</i>. American Physical Society, 2011. <a href="https://doi.org/10.1103/PhysRevLett.107.113601">https://doi.org/10.1103/PhysRevLett.107.113601</a>. Eichler, Christopher, et al. “Observation of Two-Mode Squeezing in the Microwave Frequency Domain.” <i>Physical Review Letters</i>, vol. 107, no. 11, American Physical Society, 2011, doi:<a href="https://doi.org/10.1103/PhysRevLett.107.113601">10.1103/PhysRevLett.107.113601</a>. C. Eichler, D. Bozyigit, C. Lang, M. Baur, L. Steffen, J.M. Fink, S. Filipp, A. Wallraff, Physical Review Letters 107 (2011). 17802018-12-11T11:53:58Z2021-01-12T06:53:09Z