for the following implementation of FANOUT using Toffoli gates, I'm confused about the follows:

enter image description here

  1. "the second bit being the input to the FANOUT and the other two bits standard ancilla states" - does it mean that the second bit is also the input to the other two ancilla states? Why do ancilla states require any inputs, aren't they pre-determined?
  2. Why does the output from FANOUT appear on the second and third bits? How do we extract and use this output? I learned FANOUT with the following definition and diagram. enter image description here Thus, is the value of a outputted from our circuit with Toffoli gate the value of N in the above diagram? Isn't a either 0 or 1? Then does it mean the value for fan-out can only be 0 and 1? I didn't think so as it's there are clearly more than 1 gate from fan-out in the above diagram.
  • \$\begingroup\$ 1) It looks like this question would be far better suited to Quantum Computing SE. 2) There is already an answer over there that looks like it might help you out. 3) I'm no expert on quantum computing, but it looks like FANOUT is the name of a specific operation in Quantum Computing, and it's a very different thing from fan-out as defined in electrical engineering. \$\endgroup\$
    – Mr. Snrub
    Aug 21 '21 at 5:40

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