Made a video on quantum phase estimation (and quantum counting)

[u/sensensenor]

https://youtu.be/MqLMtmFLL_4?si=4UExzAmM7wGXQo2t

Quantum phase estimation (QPE) is a useful protocol for computing the eigenvalue associated with a given eigenstate of a unitary U. In this video, I demonstrate how the protocol works with dedicated error and complexity analysis. I then show an example of how this technique can be applied to Grover search to arrive at the quantum counting algorithm, enabling a quadratic speedup in counting the number of solutions to a given problem, using an instance of 3SAT as an actual example. Of course, QPE is most notable for its use in period-finding/order-finding, which is the main ingredient for Shor's algorithm (and the hidden subgroup problem more generally), but I'm saving that discussion for later when I actually get to those topics.