There are numerous questions that asks about practical application demonstration of the Grover algorithm for arrays and databases.

However examples are not seen anywhere.

While searching for its practicality, I came across with study Is Quantum Search Practical which states that creation of the oracle is a hardware level aspect (section 4 - Oracle implementation).

Can I get please get some support in clarifying this?

  • $\begingroup$ Although the quantum speedup of Grover Aalgorithm is universal, the author certainly do not know which exact problem do you want to solve. So, an oracle is needed. otherwise maybe he has to enumerate all kinds of problems. $\endgroup$ – Yitian Wang Nov 24 '20 at 1:11
  • $\begingroup$ Hi @YitianWang Appreciate your support. Do you have a clear understanding of creating a proper oracle for a question. Because I want to learn how to make one for atleast one question. $\endgroup$ – Adhisha Gammanpila Nov 24 '20 at 7:28
  • $\begingroup$ This question (quantumcomputing.stackexchange.com/questions/14787/…) is an example. When I was writing the code for Grover search, the oracle of mine is simply a number and the rest job is to compare if it is identical to any one of the states(Hadamard acts on register 1 and initialize register to a specific state like $|1101\rangle$ and compare if register 1 contains this state). $\endgroup$ – Yitian Wang Nov 24 '20 at 7:45

Typically the oracle is a reversible circuit that implements some classical pass/fail check. In order to query the circuit under superposition, it has to be run on a quantum computer instead of a classical computer. That's all the authors mean when they say quantum hardware is required.

  • $\begingroup$ Hi @craig, thank you very much. Craig is there a way to find out "How I could build such an oracle" because this question is really a stress to figure out or any support directions to clarify ? $\endgroup$ – Adhisha Gammanpila Nov 23 '20 at 19:58
  • $\begingroup$ @AdhishaGammanpila You build it the same you build any other function using a circuit, out of Toffolis and CNOTs and NOTs. $\endgroup$ – Craig Gidney Nov 23 '20 at 20:52

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