2.5 - Reversibility & Scratch Qubits & abs()

The lecture slides are available here Download here.

This quantum computing lecture focuses on the importance of reversibility in quantum processing and introduces the concept of scratch qubits to achieve it.

A motivating example is presented using the absolute value function abs(a) to illustrate the difficulties in achieving reversibility. The solution lies in using scratch qubits, which temporarily store information such as the sign of an integer, enabling otherwise irreversible operations to become reversible. We explore the entanglement between scratch qubits and sign qubits, illustrating how they work together to preserve information during quantum computation.