English: The state labeled "EPR Pair" is a two-qubit entangled state with one qubit on each wire. A CNOT operation with the first qubit as control, followed by a Hadamard transform on the first qubit, produces an unentangled (product) state of the two qubits |a> and |b>, each of which are in exactly one of the computational basis states |0> or |1>. The mapping is unique so the circuit uniquely takes Bell Basis states to two-qubit Computational Basis states (in other words this circuit is a change of basis).
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A simple quantum circuit that maps one of the four EPR pairs into one of the four two-qubit computational basis states. The circuit consists of a CNOT gate followed by a Hadamard operation. In the outputs, a and b take on values of 0 or 1.