Added U1, U2 and U3 deprecation warnings into Circuit Library #8391
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Co-authored-by: Julien Gacon <gaconju@gmail.com>
…mo-Mijares-Vilarino/qiskit-terra into add-u1-u2-u3-deprecation
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I don't quite understand what's happening with doc generation. Now, when running Maybe it has something to do with a new version of |
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I believe that problem is fixed in #8392 and is not due to your changes 🙂 |
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The overall changes LGTM. I think it would be very nice if the warning directly shows how to replace the gate usage -- at least that's what I would be most interested in! The other relations with more gates might be better kept in the Examples section?
So it could look something like
.. warning::
... what you have ...
.. code-block:: python
circuit = QuantumCircuit(1)
circuit.p(lambda, 0) # or circuit.u(0, 0, lambda)
and then in the Examples section add the formulas you added?
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While I was moving the formulas to |
Co-authored-by: Julien Gacon <gaconju@gmail.com>
| @@ -49,11 +61,24 @@ class U2Gate(Gate): | |||
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| **Examples:** | |||
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| .. math:: | |||
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| U2(\phi,\lambda) = RZ(\phi) RY\left(\frac{\pi}{2}\right) RZ(\lambda) | |||
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I think this first equivalence with RZ RY RZ misses a global phase, doesn't it?
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I hadn't actually checked that one (trusted it to be correct but seems that was an error on my part 🤦♂️) but you are correct.
| U3(\theta, \phi, \lambda) = e^{i \frac{\pi + \theta}{2}} P(\phi + \pi) \sqrt{X} | ||
| P(\theta + \pi) \sqrt{X} P(\lambda) |
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Also here the global phase doesn't seem to match (or maybe I have a typo!)
>>> decomp = np.exp(0.5j * (np.pi + th)) * np.dot(PhaseGate(phi + np.pi), np.dot(SXGate(), np.dot(PhaseGate(th + np.pi), np.dot(SXGate(), PhaseGate(lam)))))
>>> decomp
array([[-0.53350621-0.71685923j, 0.22160969+0.39034999j],
[ 0.23851082-0.38025854j, 0.56442266-0.69277925j]])
>>> u3 = U3Gate(th, phi, lam).to_matrix()
>>> u3 # matrix doesn't match decomp
array([[ 0.89359724+0.j , -0.44545363-0.05527232j],
[ 0.1626514 +0.41836406j, 0.21878112+0.86640109j]])
>>> Operator(u3).equiv(decomp) # but it is equivalent -- hence a global phase difference exists
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That's because I forgot to add a minus sign to the global phase 😅. The correct phase is
…mo-Mijares-Vilarino/qiskit-terra into add-u1-u2-u3-deprecation
Summary
Added a deprecation warning in the circuit library pages of
U1Gate,U2GateandU3Gate.Details and comments
Along with the warning, I also included some equivalences, most of which are taken from the Summary of Quantum Operators tutorial from Qiskit-tutorials with some corrections.