Coherently Searching for Compact Dark Matter using Gravitationally Lensed Fast Radio Bursts with CHIME

The Canadian Hydrogen Intensity Mapping Experiment (CHIME) is observing several Fast Radio Bursts (FRBs) a day across a bandwidth of 400-800 MHz. Searches for gravitationally lensed FRBs have the potential to detect dark compact objects, such as primordial black holes. These microlensed FRB searches can constrain the fraction of dark matter from these compact objects at cosmological distances and in a mass regime that is difficult to probe with other techniques. We employ a novel search method to coherently search for lensing signatures by time-lag correlating the fluctuations of the electric field of an FRB and its possible image. This allows for unambiguous image detections in the time-lag domain without needing CHIME to angularly resolve the image positions in the sky. This method searches for gravitationally lensed FRBs on timescales of nanoseconds to milliseconds, corresponding to a search for compact objects between 10^-4 to 10² solar masses. I present the results of the CHIME/FRB gravitational lensing search with our initial set of ~100 FRB events. We find evidence for diffractive scintillation in some FRBs but no detections of a gravitational lens in this initial search. The search will soon be extended on a source sample an order of magnitude larger.