Qiskit's unitary like function

[nkushida-oqc]

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Describe the feature

In CUDA-Q, cudaq.register_operation() allows us to create a user-defined gate. However, this function doesn't seem to work dynamically.

At the same time, the "unitary" function in Qiskit can be used to apply a dynamically computed gate: https://docs.quantum.ibm.com/guides/synthesize-unitary-operators.

One of the targets I have in mind is AQCE (https://arxiv.org/pdf/2112.14524), which repeatedly generates user-defined (2-qubit) gates. I might be able to circumvent this issue, but if there is such a function, the implementation should be much easier.