Qubits, Gates, and Circuits
Daniel D. Stancil, Gregory T. Byrd · 2022
Digital systems that are most familiar are based on binary digits, or “bits.” Quantum computing is different from classical computing in a number of significant ways. The fundamental unit of information in quantum computing is the qubit (pronounced “KEW-bit”), short for quantum bit. The capabilities and behavior of qubits are quite different than bits, and the authors begin by pointing out and discussing the key differences as a launching point for their study of quantum computing. It is also possible to have gates with multiple qubits as inputs. However, unlike classical multi-bit gates, the fact that quantum gates are reversible requires that there must be the same number of output qubits as input qubits. The authors explore some common two-qubit gates. With a better understanding of quantum states and operations, they are now ready to construct a proof of the no-cloning theorem.