11.3 Oracles
An oracle determines whether some condition is true
or not. We have seen these many times, for example, in the code if x < y. When
we use in to test list membership, we are using an oracle. We also
use an oracle to answer the question, “Is this item in that collection?”.
In practice, the code using the oracle doesn’t necessarily have to return True or False. If I am searching for an integer
in a list of positive numbers, the code might negate the integer’s sign if it is a match. If it
is not the value I am seeking, it leaves the sign alone.
In section 11.1, I focused on how many “==”
comparisons we made in each version of the find_number
function. Put another way, “how many times do I need to call the ‘==’ oracle?
”.
In the Grover search algorithm, the oracle is tuned to do something special for the item we ...
