I have a question about the implementation of the controlled unitary $e^{iAt}$, from the paper [Demonstration of a Quantum Circuit Design Methodology for Multiple Regression] 1, using the Qiskit framework. In this paper a 4x4 Hermitian matrix A is transformed into 4x4 unitary and then decomposed by applying the GLOA algorithm. I'm not interested in this particular example but rather in general implementation of the arbitrary unitary by using qiskit. However, it is convenient to use this case as an example. In this paper we have series of controlled 4x4 unitary operators implemented according to the phase estimation algorithm. Since the resulting circuit is given in the paper, I have successfully implemented the unitary but I have a difficult time to apply the controlled action of the given unitary in qiskit framework. In another word, how can I implement a controlled unitary for some arbitrary A? Should I use a given circuit from the paper and the apply a control to each gate from the circuit or there is another way? Thanks in advance. Sorry for bad grammar.

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