Framework for generalized measurements
It would be great if one could perform measurements other than Pauli bases, like arbitrary projection-valued or positive-operator valued measurements.
If this is somehow possible with only currently available measurement operations, it would be great if that were explained somewhere.
General projective measurements can be implemented by transforming the state, performing a Pauli-basis measurement, and undoing the transformation. POVMs can also be implemented, although in general the use of ancilla qubits is required.
Generally, quantum algorithms are written in terms of measurements in the computational (Pauli Z) basis, since most types of quantum computers only offer this specific measurement. For Q#, we’ve expanded this to all Pauli bases and to arbitrary multi-qubit measurements.
Extending to general POVMs isn’t something we’ve seen a need for until your request. If there are a large number of upvotes, we’ll consider adding library routines for generalized measurements — or perhaps you or someone else will write these routines and contribute them?