Question

Suppose you are given an endless supply of qubits in the state (1/√2)|00>+(e^iϕ/√2)|10>. To estimate the phase angle ϕ, you run Fourier sampling (i.e. Hadamard on each qubit followed by a standard basis measurement) on this state repeatedly. After 100,000,000 measurements, you find that the outcome 01 never occurred. What is ϕ? Please provide your answer in the range ϕ∈[0,2π).

Answer 1

The phase will be 0.