Implement comparison between QuantumScript classes with qml.equal

[albi3ro]

Currently, we can use qml.equal to compare operations and measurements:

>>> qml.equal(qml.RX(1.2, wires=0), qml.RX(1.2, wires=0))
True
>>> qml.equal(qml.probs(wires=(0,1)), qml.probs(wires=(0,1)) )
True

but we cannot currently compare our circuit object, qml.tape.QuantumScript.

To add comparison support, we would need to register a new dispatch for the _equal single dispatch function:

pennylane/pennylane/ops/functions/equal.py

Line 159 in deaf387

def _equal(

This function

def _equal(op1 : qml.tape.QuantumScript, op2 : qml.tape.QuantumScript,
    check_interface=True,
    check_trainability=True,
    rtol=1e-5,
    atol=1e-9,
    ) -> bool :

Should return True if:

• all operations are equal, see https://docs.pennylane.ai/en/stable/code/api/pennylane.tape.QuantumScript.html#pennylane.tape.QuantumScript.operations
• all measurements are equal, see https://docs.pennylane.ai/en/stable/code/api/pennylane.tape.QuantumScript.html#pennylane.tape.QuantumScript.measurements
• The shots are equal, see https://docs.pennylane.ai/en/stable/code/api/pennylane.tape.QuantumScript.html#pennylane.tape.QuantumScript.shots
• The trainable_params are equal, see https://docs.pennylane.ai/en/stable/code/api/pennylane.tape.QuantumScript.html#pennylane.tape.QuantumScript.trainable_params

And False otherwise.

A PR implementing this should also update the docstring for qml.equal and include unit tests for comparison.

Example of desired behavior:

>>> tape1 = qml.tape.QuantumScript([qml.PauliX(0), qml.RX(1.2, wires=0)], [qml.expval(qml.PauliZ(0))], shots=10)
>>> tape2 = qml.tape.QuantumScript([qml.PauliX(0)], [qml.expval(qml.PauliZ(0))], shots=10)
>>> qml.equal(tape1, tape2)
False
>>> qml.equal(tape1, tape1)
True
>>> tape3 = qml.tape.QuantumScript([qml.PauliX(0)], [qml.expval(qml.PauliZ(0))], shots=None)
>>> qml.equal(tape2, tape3)
False
>>> tape4 = qml.tape.QuantumScript([qml.PauliX(0), qml.RX(1.2+1e-6, wires=0)], [qml.expval(qml.PauliZ(0))], shots=10)
>>> qml.equal(tape1, tape4, atol=1e-5)
True
>>> qml.equal(tape1, tape4, atol=1e-7)
False

[minhtriet]

I would like to work on this if you don't mind

[albi3ro]

Thanks @minhtriet . Let me know if you have any further questions.

[minhtriet]

Hi @albi3ro, in your example

>>> qml.equal(tape1, tape4, atol=1e-7)
False

did you mean, perhaps

>>> qml.equal(tape1, tape4, rtol=0, atol=1e-7)
False

Right now rtol is default to 1e-5, which makes the test return True

[minhtriet]

I think we could close it this @albi3ro :)

[albi3ro]

Thanks for the PR @minhtriet 🎉