kaldag

Warning on `add_bits` with layout information

3

### Summary The method `add_bits` does not check if the circuit has `layout` information. The layout information is not updated when the method `add_bits` is called by a circuit already...

added num_physical_qubits to qasm3_load

2

### Summary fixes #14435 ### Details and comments

Variance return along with sampled expectation

2

Addresses #15179. Its an elementary implementation. Applicable only for single Pauli strings.