From: 3blue1brown
The physics puzzle involving two colliding blocks and a wall, which famously computes digits of Pi, has a secret connection to quantum computing [00:00:26]. This connection was a fact unknown to the creator of the original video when it was first posted, and it was suspected no one else in the world knew about it at that time [00:00:20].
Relation to Grover’s Algorithm
More specifically, this block collision puzzle is connected to Grover’s Algorithm for Search [00:00:29]. The reason why the Pi digits appear when the mass ratio increases by powers of 100 (as opposed to powers of 10, which might be expected in base 10) is intimately connected with the fact that search algorithms can be faster for quantum computers than for classical computers [00:04:13].
Understanding Quantum Computing Through the Puzzle
Studying the solution to the block collision puzzle is suggested as a good way to understand what quantum computing even is [00:04:03]. The key step in solving the block problem, which involves packaging the changing velocities into a single point in a higher-dimensional “state space,” holds within it the key connection to the quantum computing parallel [00:09:02].
Future Exploration
A subsequent video plans to explain the basics of quantum computing, what Grover’s algorithm is, and how these two seemingly unrelated topics (colliding blocks and quantum computing) are secretly the same thing [00:26:34]. This explanation will be done with the help of theoretical physicist Adam Brown, who noticed the connection [00:05:15].
Purity Exposing Hidden Connections
The deeper reason for abstracting away from the messiness of the real world in physics problems, such as the idealized assumptions in the block collision puzzle, is that purity can expose hidden connections [00:25:59]. Distilling a problem into its core essence can reveal these connections, allowing mathematicians to make progress by understanding how a hard problem in one context might be clearer in another setting [00:26:57]. The analogy between the colliding blocks and Grover’s algorithm is an example of such a hidden connection [00:26:34].