Compact, low-threshold squeezed light source

Abstract

Strongly squeezed light finds many important applications within the fields of quantum metrology, quantum communication and quantum computation. However, due to the bulkiness and complexity of most squeezed light sources of today, they are still not a standard tool in quantum optics labs. We have taken the first steps in realizing a compact, high-performance 1550 nm squeezing source based on commercially available fiber components combined with a free-space double-resonant parametric down-conversion source. The whole setup, including single-pass second-harmonic generation in a waveguide, fits on a small breadboard and produces 9.3 dB of squeezing at a 5 MHz sidebandfrequency. The setup is currently limited by phase noise, but further optimization and development should allow for a 19" sized turn-key squeezing source capable of delivering more than 10 dB of squeezing.

40 km Fiber Transmission of Squeezed Light Measured with a Real Local Oscillator

“…Here, 𝜂 is the overall efficiency, 𝐹 𝑔 = √︁ 𝑃 pump /𝑃 threshold with 𝑃 pump being the optical power of the pump field coupled into the squeezed light source and 𝑃 threshold 5.12 mW [27] the pump power where the lasing threshold is reached, 𝑓 = 12.2 MHz is the measurement frequency, 𝑓 sqz 66 MHz [27] is the half-width-half-maximum of the squeezed light source's frequency response and 𝜎 is the standard deviation of the phase noise. 𝑉 0 ± are the variances with zero phase noise.…”

“…The pilot tone is combined with the squeezed light mode, residing as a single frequency sideband, thereby providing a frequency and phase reference for the local oscillator upon reception at the homodyne detection station. We note that pilot tones are an essential part of the coherent control scheme commonly used to actively control squeezed light sources [4,26,27] and, thus, they are readily available in many squeezed light experiments. At the receiver station, the frequency offset and phase difference relative to the real local oscillator are measured through interference at a beam splitter as shown in the figure, and the resulting signals are subsequently used to control the frequency and phase of the real local oscillator mode to compensate for any phase and frequency drifts.…”

Driven quadrature and spin squeezing in a cavity-coupled ensemble of two-level states

“…Quadrature squeezed light is an important experimental resource in quantum optics with a number of applications ranging from enhancing interferometry beyond the shot-noise limit [1,2], to its use in generating entangled continuous-variable states for quantum information protocols [3,4]. Due to its utility, there is justifiable motivation to not only generate larger squeezing magnitudes, necessary in particular for fault-tolerant continuous-variable quantum computing [5], but also in expanding its bandwidth [6], and in optimizing its experimental efficiency and integrability [7]. By making squeezed light sources more accessible and practically implementable, their benefits may be reaped in both routine spectroscopy and interferometry [8,9], while further spurring the development of hybrid continuous/discrete variable quantum information protocols [10], and optical sensing schemes that go beyond the classical limits [11].…”

“…8.Plot of the (a) minimum steady-state quadrature-variance of the cavity field and (b) the steady-state photon number of the cavity field, for a range of γ * 2 /γ1 fractions, which are annotated in the plots. The same parameters as in fig (7). are used for N = 10 8 and z = 10 −6 .…”

4-dB Quadrature Squeezing With Fiber-Coupled PPLN Ridge Waveguide Module

“…This is because guided-wave components have larger loss and lower durability for intense pump beams compared to free space optics. OPOs with capability of direct coupling with optical fibers [10], [11] and a compact OPO on a breadboard [12] have been proposed, but the need to control and adjust the cavity length could be an obstacle to scaling up of quantum circuits in the future.…”