Quantum sensing pushes measurement precision toward the Heisenberg limit — sensitivity scaling as 1/N² rather than the classical 1/N. The standard approach distributes entangled photons across spatial modes. More modes, more photons, more precision. But the spatial resources are fixed: you have a finite number of sensors, a finite number of arms.
This paper exploits a resource that was sitting unused: time. By entangling measurements across repetitions — temporal multiplexing — the authors achieve Heisenberg scaling simultaneously in photon number N, spatial modes M, and measurement repetitions R. The sensitivity approaches 1/(NMR)², a triple product that previous protocols never achieved because they treated repetitions as classical averages.
The protocol is experimentally feasible: it requires homodyne detection and a looped photonic architecture, and the advantage persists under optical loss. The Bogoliubov transformation formalism proves optimality within Gaussian states — you cannot do better with this class of quantum light.
The insight is that temporal entanglement is free. Every previous distributed sensing protocol entangled across space but averaged across time, discarding temporal correlations that carry metrological information. Repetitions are not just statistics — they are quantum resources. Using them as such doesn't require new hardware. It requires recognizing that the dimension you were averaging over was the dimension you should have been entangling across.