This is one in a series of posts working through the exercises in the Quantum Country online introduction to quantum computing and related topics. The exercises in the original document are not numbered; I have added my own numbers for convenience in referring to them.
Exercise 15. Find a way of implementing a NAND gate using just a single Toffoli gate and no other quantum gates.
Answer: As described in the previous exercise, a Toffoli gate with inputs , , and acts as a NAND gate producing the target output .