Environment

• Qiskit version: 2.0.0rc1
• Python version: 3.9
• Operating system: linux

What is happening?

Running transpile with multiprocessing and fractional gates triggers a TypeError: cannot pickle 'qiskit._accelerate.two_qubit_decompose.TwoQubitControlledUDecomposer' object.

How can we reproduce the issue?

Discovered running the following qiskit-aer unit test with multiprocessing: test/terra/backends/aer_simulator/test_executors.py

What should happen?

No error

Any suggestions?

Add pickle support