Creating the four Bell states with quantum computing in Qiskit. https://quantumcomputing.stackexchange.com/a/2260

bell-states.py

def four_bell_states():
    """
    Create all 4 Bell states.
    https://quantumcomputing.stackexchange.com/a/2260
    """

    # [00, 11] positive
    qc = QuantumCircuit(2)
    qc.h(0)
    qc.cx(0, 1)
    execute_bell(qc, '00-11')

    # [01, 10] positive
    qc = QuantumCircuit(2)
    qc.h(0)
    qc.cx(0, 1)
    qc.x(1)
    execute_bell(qc, '01-10')

    # [00, 11] negative
    qc = QuantumCircuit(2)
    qc.h(0)
    qc.cx(0, 1)
    qc.z(0)
    execute_bell(qc, '11-00')

    # [01, 10] negative
    qc = QuantumCircuit(2)
    qc.h(0)
    qc.cx(0, 1)
    qc.z(0)
    qc.x(1)
    execute_bell(qc, '10-01')
    
def execute_bell(qc, name):
    simulator = Aer.get_backend('statevector_simulator')
    qobj = assemble(qc)
    result = simulator.run(qobj).result()
    output_state = result.get_statevector(qc)
    print(output_state)
    figure = plot_histogram(result.get_counts())
    figure.savefig('bellstate-{}.png'.format(name))

[0.70710678+0.j 0.        +0.j 0.        +0.j 0.70710678+0.j]
[0.        +0.j 0.70710678+0.j 0.70710678+0.j 0.        +0.j]
[ 0.70710678+0.j -0.        +0.j  0.        +0.j -0.70710678+0.j]
[ 0.        +0.j -0.70710678+0.j  0.70710678+0.j -0.        +0.j]