Bad Qubits — Learn Quantum by Doing

Multiple choice

The n-qubit Pauli group P_n consists of all tensor products of single-qubit Paulis {I, X, Y, Z} together with an overall phase from {+1, -1, +i, -i}. How many elements does P_n have?

2^(2n)
2^(2n+2)
2^n
4^n