Quantum-Assisted Optical Interferometers: Instrument Requirements

Improved determination of photon wave-functions could provide high-resolution observations in the optical, benefiting numerous topics in astrophysics and cosmology. It has been recently suggested that optical interferometers would not require a phase-stable optical link between the stations if instead sources of quantum-mechanically entangled pairs could be provided to them, enabling extra-long baselines. We developed a new variation of this idea, suggesting that two photons from different sources could be interfered at two decoupled stations, requiring only a slow classical information link between them. We show that this approach could allow robust high-precision measurements of the relative astrometry of the two sources, with a basic calculation giving angular precision of $10 \ \mu$as in a few hours' observation of two bright stars. We also give requirements on the instrument for these observations, in particular on its temporal and spectral resolution. Finally, we discuss possible technologies for the instrument implementation and first proof-of-principle experiments.