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An oracle is a "black box" operation (function) that is used as an input to an another algorithm (for example Deutch-Jozsa, Grover etc.). A parameter or feature of the Oracle is infered by the algorithm.

3 votes
Accepted

Construct a standard oracle using a phase oracle

Yes - put the control bit in the state $H\lvert b\rangle$, with $H$ the Hadamard transform. Then, the controlled-$U_f$ gate will transform $(H\lvert b\rangle)\otimes\lvert i\rangle$ into $(H\lvert b\o …
Norbert Schuch's user avatar
5 votes

How would I implement the quantum oracle in Deutsch's algorithm?

There is no way to build the oracle in a way which would not defeat the point of Deutsch's algorithm - that's why it is an oracle-based algorithm. The only way would be if you would come up with an i …
Norbert Schuch's user avatar
2 votes

Is there a way to construct a quantum circuit/oracle to check if 2 qubits in an unknown pure...

No. For instance, if I either give you $|00\rangle$ or $|11\rangle$ with 50% probability each, or $|00\rangle\pm|11\rangle$ with 50% probability each, there is no way to distinguish these two cases - …
Norbert Schuch's user avatar
5 votes

Show that transformation $U_f: \left| x, y \right\rangle \to \left| x, y \oplus f(x) \right\...

As it happens, this $U_f$ is its own inverse. So to show that it is unitary, you need to show that $U_fU_f=I$ $U_f^\dagger = U_f$ (that is, $U_f$ is its own inverse). Both of these are straightfor …
Norbert Schuch's user avatar