Is it correct to implement a balanced Deutsch-Jozsa oracle by CNOTing the first qubit with the last one (the ancilla qubit), it would get you a balanced output.

And if it's valid why is it not commonly implemented like this in examples and books.

  • 2
    $\begingroup$ This seems a bit unclear, would you be able to elaborate on the construction of your proposed oracle? $\endgroup$ Sep 8, 2021 at 5:43
  • $\begingroup$ basically CNOT(Qubit0,AncillaQubit) $\endgroup$
    – user18226
    Sep 8, 2021 at 7:00

1 Answer 1


It is an implementation of a balanced oracle. However, the whole point of the Deutsch-Jozsa oracle is that you should not know in advance which oracle is being used. If you know the oracle, you'd already know the answer!

Furthermore, the whole interest in Deutsch-Jozsa as compared to Deutsch is the scaling, i.e. wanting to be able to use oracles with an increasing size of input, and still only requiring one call to the oracle.


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