Up to this point, you have manipulated individual qubits and created entanglement using specific gate pairs. This chapter shifts focus to the arrangement of these elements into complete quantum circuits. We will establish the standard conventions for circuit diagrams, allowing you to visualize how quantum information moves through a system over time.

You will also encounter the constraints that govern quantum software design. A primary limitation is the no-cloning theorem, which states that an arbitrary quantum state $\lvert \psi \rangle$ cannot be perfectly copied. This theorem prevents the use of classical "copy and paste" logic in quantum algorithms. Instead, you must rely on alternative protocols to move information.

We will implement two such protocols: superdense coding and quantum teleportation. These examples demonstrate how to utilize entanglement as a resource for communication. By the end of this chapter, you will be able to construct and simulate these circuits using Python, verifying that the information arrives at its destination without violating physical laws.