Mechanical Squeezing via Unstable Dynamics in a Microcavity

A system of linearly coupled quantum harmonic oscillators can be dynamically unstable, even in the absence of dissipation (see Ref. [1] and references therein). Although dynamically unstable regimes are often considered undesirable [2], they can also be a resource. In this Letter, we show how to engineer and harness unstable multimode dynamics in a linear optomechanical system to induce strong mechanical squeezing. Preparing squeezed states of a mechanical oscillator-quantum states with position uncertainty smaller than its zero-point motion-is a key aim of optomechanics [3], as these states lie at the heart of