  We propose and develop a measurement scheme for quantum field theory (QFT) in
curved spacetimes, in which the QFT of interest, the "system", is dynamically
coupled to another, the "probe", in a compact spacetime region. Measurements of
observables in the probe system then serve as proxy measurements of observables
in the system, under a correspondence which depends also on a preparation state
of the probe theory. All our constructions are local and covariant, and the
conditions may be stated abstractly in the framework of algebraic quantum field
theory (AQFT). The induced system observables corresponding to probe
observables may be localized in the causal hull of the coupling region and are
typically less sharp than the probe observable, but more sharp than the actual
measurement on the coupled theory. A formula is given for the post-selected
system state, conditioned on measurement outcomes, which is closely related to
the notion of an instrument as introduced by Davies and Lewis. This formula has
the important property that individual measurements form consistent composites,
provided that their coupling regions can be causally ordered and a certain
causal factorisation property holds for the dynamics; the composite is
independent of the causal order chosen if more than one exists. The general
framework is amenable to calculation, as is shown in a specific example. This
contribution reports on joint work with R. Verch, arXiv:1810.06512.
