A quantum particle is prepared in an unknown state. It is then measured with the outcome |0). (a) Which of the following could be its initial state before the measurement: |0), → 10) + 1). {10) + $11) or (10) + 1))? (b) If you tried to measure the same particle a second time, can you narrow down what the initial state was? (c) Another particle is prepared in the same unknown state. It is measured in the |1) state. What can you say about the initial state now?

A quantum particle is prepared in an unknown state. It is then measured with the outcome |0). (a) Which of the following could be its initial state before the measurement: |0), → 10) + 1). {10) + $11) or (10) + 1))? (b) If you tried to measure the same particle a second time, can you narrow down what the initial state was? (c) Another particle is prepared in the same unknown state. It is measured in the |1) state. What can you say about the initial state now?