Two boxes each produce a stream of qubits. Box A produces the qubits all in the state . Box B randomly produces qubits in states |0and |1, each with probability 1/2. We have one of the boxes, but it...

Two boxes each produce a stream of qubits. Box A produces the qubits all in the state
. Box B randomly produces qubits in states |0and |1, each with probability 1/2. We have one of the boxes, but it is unmarked and so we do not know which kind it is. Describe an experiment on the qubits that can tell the difference between box A and box B. Can you reliably tell the difference between the boxes by examining only one of the qubits?