  In practice, it is quite challenging to detect a quantum property, a
microscopic property, in a macroscopic system. In our work, we construct
general proxy witnesses of quantum properties to detect their presence in
quantum systems and we do so for quantum systems which may possibly be large.
In particular, we discuss proxy witnesses for quantum properties like
unextendibility, quantum coherence, activation, steerability, and entanglement.
We apply these proxy witnesses in some widely considered examples of many-body
systems, viz., the quantum Heisenberg models, the quantum J1-J2 model.
