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Even though this seems to be a much asked basic question, I couldn't find a reputed answer to this:

  • Implement a 3-qubit Toffoli gate using 3-qubit Fredkin gates.

The best I could do was using 4 gates to give

enter image description here

  1. Can we use less than 4 gates?
  2. In the above circuit how to get rid of the garbage values?(I have heard they are bad for interference)

I am new to quantum computing so please correct me if I am asking something that doesn't make sense.

Community
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lineage
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1 Answers1

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It's not possible to implement a Toffoli using only Fredkin gates, because Fredkin gates preserve the number of 1s in the state while Toffolis do not.

Craig Gidney
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