A squeezing upgrade that could push LIGO past its quantum limits

Internal optical losses are a fundamental barrier to sensitivity in interferometric gravitational-wave detectors — every photon absorbed or scattered inside the cavity adds irreducible noise. This scheme inserts two optical parametric amplifiers into the signal-extraction cavity, squeezing light traveling in both directions simultaneously. The result is a quantum noise floor that no longer depends on the transmissivities of the arm-cavity mirrors or signal-extraction optics at high frequencies, freeing engineers from a longstanding design trade-off. Analytical results are confirmed numerically, realistic loss mechanisms are assessed, and a 'mode healing' effect is identified that suppresses losses from imperfect beam overlap — making the scheme a credible upgrade path for LIGO and next-generation observatories.