Beating the Standard Sensitivity-Bandwidth Limit of Cavity-Enhanced Interferometers with Internal Squeezed-Light Generation

Abstract

The shot-noise limited peak sensitivity of cavity-enhanced interferometric measurement devices, such as gravitational-wave detectors, can be improved by increasing the cavity finesse, even when comparing fixed intracavity light powers. For a fixed light power inside the detector, this comes at the price of a proportional reduction in the detection bandwidth. High sensitivity over a large span of signal frequencies, however, is essential for astronomical observations. It is possible to overcome this standard sensitivity-bandwidth limit using nonclassical correlations in the light field. Here, we investigate the internal squeezing approach, where the parametric amplification process creates a nonclassical correlation directly inside the interferometer cavity. We theoretically analyze the limits of the approach and measure 36% increase in the sensitivity-bandwidth product compared to the classical case. To our knowledge, this is the first experimental demonstration of an improvement in the sensitivity-bandwidth product using internal squeezing, opening the way for a new class of optomechanical force sensing devices.

Towards the Fundamental Quantum Limit of Linear Measurements of Classical Signals

“…(30), the feedback gain is frequency dependent, resulting in the sharp resonance feature. The underlying physics is similar to the intracavity squeezing studied theoretically by Peano et al [37] and experimentally by Korobko et al [38].…”

High-Efficiency Measurement of an Artificial Atom Embedded in a Parametric Amplifier

“…In contrast, the noise fluctuations do get amplified (squeezed), such that the SNR at the QPA output depends on Φ. Since amplifying the signal quadrature squeezes the photon number fluctuations in the conjugate quadrature which cause dephasing, we expect amplifier mode (Φ = 0) to minimize Γ φ and squeezer mode (Φ = π/2) to maximize it, in agreement with the comparison of Figs We note that squeezer mode is also of interest as a means of improving SNR by reducing the quantum fluctuations of the output measurement field [24,31,32]; similar insitu squeezing generation has been demonstrated in a recent optical experiment [33].…”

Designing optimal linear detectors -- a bottom-up approach

“…In this paper we introduce a general approach to realising a Heisenberg limited detector directly from its inputoutput transfer matrix. This approach leads to both minimal and non-minimal realizations: the minimal realization of the general transfer matrix exhibits internal squeezing, directly increasing the photon number fluctuation in the probe degree of freedom, as explored in [17][18][19]; the non-minimal realization begins with the minimal realization of a first-order lossless passive detector that does not saturate the Heisenberg limit, then adds a pair of auxiliary modes that result in an infinite signal amplification at DC (i.e. for low frequency signals).…”