Nano to pico degree optical astronomy: in quantum physics we trust!

In most AGNs a high pressure and low density plasma forms. The EHT has resolved such flows and could detect particles accelerated close to the horizon. For higher accretion rates, momentum is dissipated and disk-shaped structures form. Their apparent sizes are ∼10 μarcsec in nearby quasars and of ∼0.1μarcsec in of low mass X-ray binaries. Hanbury-Brown & Twiss invented intensity interferometry and measured the size of bright stars. Large telescopes, 10ps resolution photon detectors and synchronous spectrometers bring the key improvements to reach in the optical angular resolutions better than these achieved in the radio by the EHT and to reconstruct the first images of accretion disks. We already demonstrated a system of synchronized photometers and correlators providing a resolution of 20ps RMS and have designed a detector array (at the Silicon foundry), an efficient synchronous spectrometer (under test), and an FPGA-based data processing chain. All these elements will be combined in 2026 and could be used on VLT and VISTA (disks in CVs) and on VLT and ELT opening nano-degree resolution in the optical (disks in AGN, SN geometry). Extending to continental (disks in LMXB) or Earth scale infrastructures (pico-degree resolution) requires a few additional steps.