I am learning how to draw quantum circuits. I was checking the options available and I could see that Tikz and Quantikz are suitable for making circuits diagrams but I want to know if there are some tasks that Quantikz can do but Tikz cannot. Thanks.
As Michele Amoretti correctly says, Quantikz is built on top of Tikz. It cannot do anything that Tikz cannot. It is simply intended to provide a wrapper that makes it more convenient for doing the specific tasks associated with drawing quantum circuits.
More specifically, it's done in a way that I find most convenient (as the package author!). Mostly it came about because I'm writing a text book which contains hundreds of circuit diagrams, and I needed that convenience, but knowing that Tikz does a beautiful job of graphics in LaTeX.
As explained in this tutorial, Quantikz is a Tikz package that is specific for drawing quantum circuits. So they are not alternative solutions.