  Quantum interference is a central resource in many quantum-enhanced tasks,
from computation to communication protocols. While it usually occurs between
identical input photons, quantum interference can be enabled by projecting the
quantum state onto ambiguous properties that render the photons
indistinguishable, a process known as a quantum erasing. Structured light, on
the other hand, is another hallmark of photonics: it is achieved by
manipulating the degrees of freedom of light at the most basic level and
enables a multitude of applications in both classical and quantum regimes. By
combining these ideas, here we design and experimentally demonstrate a simple
and robust scheme that tailors quantum interference to engineer photonic states
with spatially structured coalescence along the transverse profile, a type of
quantum mode with no classical counterpart. To achieve this, we locally tune
the distinguishability of a photon pair via spatial structuring of their
polarisation, creating a structured quantum eraser. We believe these
spatially-engineered multi-photon quantum states may be of significance in
fields such as quantum metrology, microscopy, and communications.
