Classical register instructions for simulators

[Lolcroc]

What is the expected behavior?

QuantumCircuits are very rich in operations on qubits, but lack operations on classical bits. The feature request are classical operations (logic gates) on classical bits, such as NOT/CNOT (acting "in-place" on the classical register) that are part of the QuantumCircuit itself.

Reasoning

• Simple post-processing of measurement outcomes may be done as part of QuantumCircuit simulations
• Combined measurements may be used for classical controlled gates in the simulator (e.g. only do some Gate if cbit0 and cbit1 are both 1).

[kdk]

Thanks for bringing this up, @Lolcroc . We're planning enhanced support for classical instructions and data types as part of support for the new set of features available in OpenQASM 3 ( https://qiskit.github.io/openqasm/language/classical.html ).

[HuangJunye]

Are we still planning to fix this issue for 0.20?

[jakelishman]

No, this is dynamics circuit work, so it's pushed til at least 0.21.