Is there code to generate the statevector amplitude histogram for a circuit outside the Composer?

Question

When using the IBM Composer, in the bottom left of our screen we have access to two histograms. A theoretical probability histogram and a statevector amplitude histogram. I'm looking for ways to create these same visualizations outside of the Composer (So in the Lab or other Jupyter Notebook). I know that for an experimental probability histogram I can measure my qubits using an ideal simulator like the 'aer_simulator' and then use plot_histogram, but I have not found anything that would portray the statevector amplitude histogram.

I assume there is code to generate this, and I'm not asking for anything that has not been released or involves proprietary information, but for it to be a part of their constant visualization, I simply assumed there was code to generate it, but I cannot seem to find it! Thank you for your guidance!

To see which visualization I am referring to scroll down to the Statevector View section of this link.

Answer 1

In Qiskit, there are two easy ways to get the state vector of a quantum circuit.

The easiest is just

from qiskit.quantum_info import Statevector
Statevector(mycircuit)

This does not create a histogram of results, but actually keep track of the state vector.

You can also use a simulator, with I think is faster for larger programs.

def get_statevector(circuit):
    sim = Aer.get_backend('aer_simulator')
    circuit.save_statevector()
    result = execute(circuit, sim).result()
    return result.get_statevector()

The simulator keeps track and dumps the actual statevector, not a histogram.