Abstract
We propose a quantum teleportation-based speed meter for interferometric displacement sensing. Two equivalent implementations are presented: an online approach that uses real-time displacement operation and an offline approach that relies on post-processing. Both implementations reduce quantum radiation pressure noise and surpass the standard quantum limit of measuring displacement. We discuss potential applications to gravitational-wave detectors, where our scheme enhances low-frequency sensitivity without requiring modifications to the core optics of a conventional Michelson interferometer (e.g., substrate or coating properties). This approach offers a new path to back-action evasion enabled by quantum entanglement.