Undefined gates for cr2, cr4, cr8 and crz

[Kaustuvi]

Hi! I have the following program :

var QuantumCircuit = require("../../lib/debug.js");

var circ = new QuantumCircuit();

circ.addGate("cr2", -1, [0, 1, 2]);
circ.addMeasure(1, "c", 3);

circ.run();

console.log("");
console.log(circ.exportCirq());

The exported cirq program is as follows:

import cirq
import numpy as np

q = [cirq.NamedQubit('q' + str(i)) for i in range(3)]

circuit = cirq.Circuit.from_ops(
    cu1(np.pi / 2)(q[0], q[1], q[2]),
    cirq.measure(q[1], key='c3')
)

simulator = cirq.google.XmonSimulator()
result = simulator.run(circuit)
print(result)

The gate cu1 does not belong to cirq's gate set and hence will result in an error if I try to run this program in cirq. cu1 or better still crz with an angle pi/2 (since cr2 is a controlled-RZ rotation with angle pi/2) needs to be defined in order to make the program work. Same goes for cr4 and cr8.

Another issue I came across was with the gate crz. If I have the following program:

var QuantumCircuit = require("../../lib/debug.js");

var circ = new QuantumCircuit();

circ.addGate("crz", -1, [0, 1], {
    params: {
        phi: "pi/2"
    }
});
circ.addMeasure(1, "c", 3);

This outputs the following cirq program:

import cirq
import numpy as np

def crz(p_phi):
    return cirq.TwoQubitMatrixGate(np.array([ [1,0,0,0], [0,1,0,0], [0,0,1,0], [0,0,0, np.exp(1j * p_phi)] ]))

q = [cirq.NamedQubit('q' + str(i)) for i in range(2)]

circuit = cirq.Circuit.from_ops(
    cu1(np.pi / 2)(q[0], q[1]),
    cirq.measure(q[1], key='c3')
)

simulator = cirq.google.XmonSimulator()
result = simulator.run(circuit)
print(result)

The used gate is crz which is also defined but the circuit is created with cu1. I think the circuit should be created with crz.

I will raise a PR with changes that I think will solve these issues. :) Till then, please let me know if I am missing something or if there could be some other workaround. :)