This chapter covers:
- different ways to obtain information from classical functions
- the difference between function evaluations and function properties
- quantum gates that correspond to classical black box functions
- the Deutsch algorithm
- the Deutsch-Jozsa algorithm
Do you know if the number 168153 can be divided by 3? There are a number of ways to find out. For example, you can simply take a calculator and obtain the result:
168153 / 3 = 56051
The result of the division is 56051. But that was not the question. Actually, we don’t care about this result. Fortunately, thanks to this evaluation, we also know the real answer. There are no digits after the decimal point, hence we can conclude the number can indeed be divided by 3.
There is another simple approach to find the answer to this question, and you might know this simple trick: take the sum of the individual digits that compose the number, and see if that sum can be divided by 3. If so, the original number can be divided by 3 as well. Let’s to that:
1 + 6 + 8 + 1 + 5 + 3 = 24
Since 24 can indeed be divded by 3, we can conclude that 56051 can be divided by 3 as well.
The first approach (using the calculator) gave us a result of a division, and it provided us with the real answer. The second approach (sum of the individual digits) only provided the real answer, and not the outcome of the division.