  When observing a quantum field via detectors with access to only the mixed
states of spatially separated, local regions -- a ubiquitous experimental
design -- the capacity to access the full extent of distributed entanglement
can be limited, shrouded by classical correlations. By performing projective
measurements of the field external to two detection patches and classically
communicating the results, underlying pure states may be identified for which
entanglement quantification is clear. In the Gaussian continuous-variable
states of the free scalar field vacuum, this protocol uncovers a disparity
between the spacelike entanglement established within the field and that which
is locally detectable. This discrepancy is found to grow exponentially with the
separation between observation regions. The protocol developed herein offers
insight and practical guidance for clarifying the unavoidable distortion of
quantum field correlations when viewed from the vantage of a pair of local
observers.
