Use of ancillary bits in quantum computing

[BlackHole213]

How is an ancillary bit used in a logic gate? I looked at

http://en.wikipedia.org/wiki/Ancilla_(quantum_computing )

as well as Quantum Computation and Quantum Information by Nielsen and Chuang, but neither source really explained how an ancillary bit is used (in a logic gate circuit) or why it is needed. I looked at several other sites and books, but I've found that each source immediately started talking about ancillary bits without first explaining them.

Thanks.

 

[Bill_K]

Did you look in this reference? It gives a step-by-step example showing how ancillary bits may be used for error correction.

 

[BlackHole213]

Thanks! The book was extremely helpful.