  Photonic Lanterns (PLs) are tapered waveguides that gradually transition from
a multi-mode fiber geometry to a bundle of single-mode fibers (SMFs). They can
efficiently couple multi-mode telescope light into a multi-mode fiber entrance
at the focal plane and convert it into multiple single-mode beams. Thus, each
SMF samples its unique mode (lantern principal mode) of the telescope light in
the pupil, analogous to subapertures in aperture masking interferometry (AMI).
Coherent imaging with PLs can be enabled by interfering SMF outputs and
applying phase modulation, which can be achieved using a photonic chip beam
combiner at the backend (e.g., the ABCD beam combiner). In this study, we
investigate the potential of coherent imaging by interfering SMF outputs of a
PL with a single telescope. We demonstrate that the visibilities that can be
measured from a PL are mutual intensities incident on the pupil weighted by the
cross-correlation of a pair of lantern modes. From numerically simulated
lantern principal modes of a 6-port PL, we find that interferometric
observables using a PL behave similarly to separated-aperture visibilities for
simple models on small angular scales ($<\lambda/D$) but with greater
sensitivity to symmetries and capability to break phase angle degeneracies.
Furthermore, we present simulated observations with wavefront errors and
compare them to AMI. Despite the redundancy caused by extended lantern
principal modes, spatial filtering offers stability to wavefront errors. Our
simulated observations suggest that PLs may offer significant benefits in the
photon noise-limited regime and in resolving small angular scales at low
contrast regime.
