Bad Qubits — Learn Quantum by Doing

Multiple choice

In single-qubit Quantum Signal Processing, interleaving d signal rotations W(a) with d+1 tunable Z-rotations e^{i phi_k Z}, what is the top-left entry of the resulting unitary U_phi(a) as a function of the signal a?

A degree-d polynomial P(a) in the signal a
A constant independent of a
An exponential e^{i a}
A degree-d polynomial in the phase angles phi but independent of a