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Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device

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Science Advances  23 Sep 2020:
Vol. 6, no. 39, eaba9186
DOI: 10.1126/sciadv.aba9186
  • Fig. 1 Overview of device.

    (A) Schematic of microring device showing resonator, side channel, microheater (blue), and scattering modes. (B) Optical microscope image of device. (C) Illustration of intraresonator SFWM process, showing frequency shifts ΔSPM and ΔXPM associated with self- and cross-phase modulation (SPM and XPM, respectively). (D) Representative transmission spectrum of microring device, showing three overcoupled resonances near 1550 nm.

  • Fig. 2 Quadrature squeezing.

    (A) Overview of experimental setup. Details in the main text and the Supplementary Materials. WDMs, wavelength division multiplexing components. LO, local oscillator; EDFA, erbium-doped fiber amplifier; PLL,phase-locked loop; VOA, variable optical attenuator; PC, polarization controller; PID, proportional-integral-derivative. (B) Quadrature variance (black line) relative to shot noise (gray line) as a function of time, while the local oscillator phase is ramped, exhibiting 1.0(1) dB of squeezing. Traces are obtained from the homodyne detector photocurrent fluctuations monitored on an electrical spectrum analyzer in zero-span mode at 20-MHz sideband frequency, with a resolution bandwidth of 1 MHz and a video bandwidth of 300 Hz. (C) Maximum and minimum quadrature variances as a function of pump power for the 20-MHz sideband, showing the power scaling of the squeezed and antisqueezed quadratures. The top and bottom dashed lines are obtained by fitting to Eq. 2; the shot noise level is shown (dashed line at 0 db)..

  • Fig. 3 Squeezing and antisqueezing frequency spectrum from 20 MHz to 1 GHz at different pump power levels.

    Powers listed are inferred values on-chip in the input waveguide. Dashed line is shot noise level; solid lines exhibit fits to the theoretical model (details in the Supplementary Materials), showing strong agreement with the measured data.

  • Fig. 4 Photon number difference squeezing.

    (A) Overview of experimental setup. Details in the main text and the Supplementary Materials. (B) Measured photon number difference variance VΔn as a function of mean photon number ntot, obtained by varying pump power, for coherent states (gray) and squeezed states (black) with linear fits (solid lines). The reduced slope for the squeezed state represents photon number difference squeezing. Inset: Ratio between number difference variance and mean photon number as a function of mean photon number for coherent states (gray) and squeezed states (black).

  • Fig. 5 Measured second-order correlation g(2) (Eq. 4) for the signal and idler (green and orange points, respectively) and for coherent states (gray points) for different values of photon number n.

    Data are collected over a range of pump pulse energies corresponding approximately to 0.1- to 1-nJ on-chip. Coherent state data were acquired using attenuated laser pulses and show excellent agreement with the predicted g(2) = 1 for coherent states.

Supplementary Materials

  • Supplementary Materials

    Broadband quadrature-squeezed vacuum and nonclassical photon number correlations from a nanophotonic device

    V. D. Vaidya, B. Morrison, L. G. Helt, R. Shahrokshahi, D. H. Mahler, M. J. Collins, K. Tan, J. Lavoie, A. Repingon, M. Menotti, N. Quesada, R. C. Pooser, A. E. Lita, T. Gerrits, S. W. Nam, Z. Vernon

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