I am reading the book "Quantum Computing verstehen" by Matthias Homeister.
At the moment i'm having a look at the BB84 protocol (which is described in kind of an abstract way).
In this chapter a quantum circuit is shown, describing how Alice creates and sends a qubit and how Bob measures it.
Now Alice qubit-creation step is described as:
$\text{1. generate a random classical bit } a \text{ and initialize the qubit } | x \rangle \gets |a\rangle$
$\text{2. generate a second random classical bit } a' \text{ . If } a'=1 \text{ apply the Hadamard matrix to }|a\rangle$
I'm wondering how to interpret this Hadamard-gate with two inputs, since i havent seen it with two inputs before. Is it supposed to apply the Hadamard matrix only if the second input is 1?