Matchgate simulator

[kevinsung]

What should we add?

A circuit consisting only of Clifford gates can be efficiently simulated using the StabilizerState class. There is another important class of classically simulable circuits, which are those consisting of matchgates acting between nearest-neighbor qubits on a line (see https://arxiv.org/abs/0804.4050). In the context of Qiskit, matchgates are represented by XXPlusYYGate and XXMinusYYGate. My request is to add functionality to efficiently simulate these circuits.

[ShellyGarion]

Generally, we don't have simulators in Qiskit (except of the basic ones: Statevector and StabilizerState) only in qiskit-aer.
Could you perhaps elaborate on the importance of this simulator?

[trigpolynom]

I'd like to help with this if possible. I am interested in classical simulation in general and would like to learn more about matchgates.

[trigpolynom]

What should we add?

In the context of Qiskit, matchgates are represented by XXPlusYYGate and XXMinusYYGate. My request is to add functionality to efficiently simulate these circuits.

Hi @kevinsung it seems that one can use the BasicSimulator to simulate circuits containing the gates mentioned. See below from test_standard_library.py:

def test_xx_plus_yy(self):
        self.circuit.append(lib.XXPlusYYGate(0.1, 0.2), [0, 1])
        self.circuit.measure_all()
        result = (
            BasicSimulator().run(self.circuit, shots=self.shots, seed_simulator=self.seed).result()
        )
        self.assertEqual(result.success, True)

What exactly would the simulation you have in mind look like? I'm interested in working on this and would love to collaborate. My email is [email protected] in case you want to set up some time to chat about it.