Question

Alice has a very important piece of information, which is encoded as an integer k. She is storing this number in a quantum state |ψ⟩=∑xαx|x⟩ of n qubits in such a way that if you apply QFT2n to |ψ⟩ and then measure in the standard basis, you get k with probability 99%. Her archenemy Eve sneaked into Alice's lab and, not knowing how to perform QFT, decided to destroy the information instead. She started pushing random buttons and it resulted in adding a number y to the qubits i.e.~the resulting state is |ψ′⟩=∑xαx|x+y(mod2n)⟩. Which of the following statements are true? Check all that apply.

Answer 1

Goodness.

Answer 2

please answer

Answer 3

YOU HAVE TO CHECK

If Alice now applies QFT2n and measure, she will still get k with probability 99%.

AND

If she does as in the previous option, she will get k with probability 99%.

Answer 4

thanx