When to Differentiate State |0> From State |1>

In the lesson Quantum machine learning in the NISQ era, we mentioned that high precision quantum computers must work because quantum algorithms build on precise manipulations of continuously varying parameters. Therefore, even the noise caused by heat can ruin the computation.

This is problematic because the computers we can build thus far are essentially expensive electric heaters that perform a small amount of computation as a side effect.

Our computers operate in a way that depends on the intentional loss of some information.

The $and$ operator returns an output of 1 if both input values are 1. In all other cases, we get a 0. Given the output of 0, we have no way of knowing what the input was.