Quantum Mechanics, Quantum Computing, Quantum Physics, Qubit.
qubit was measured in state |0⟩ with 100% probability, then the probabilities of measuring each |0⟩ and |1⟩ after applying the H gate become 50% and 50%. if (r₀, r₁) = (0, 1) in the initial state, i.e. our qubit was measured in state |1⟩ with 100% certainty, then the probabilities also become 50%