qiskit/releasenotes/notes/0.16/deprecate-u123-c7646ddf73bf...

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---
deprecations:
- |
The :class:`~qiskit.circuit.QuantumCircuit` methods ``u1``, ``u2`` and
``u3`` are now deprecated. Instead the following replacements can be
used.
.. code-block::
u1(theta) = p(theta) = u(0, 0, theta)
u2(phi, lam) = u(pi/2, phi, lam) = p(pi/2 + phi) sx p(pi/2 lam)
u3(theta, phi, lam) = u(theta, phi, lam) = p(phi + pi) sx p(theta + pi) sx p(lam)
The gate classes themselves, :class:`~qiskit.circuit.library.U1Gate`,
:class:`~qiskit.circuit.library.U2Gate` and :class:`~qiskit.circuit.library.U3Gate`
remain, to allow loading of old jobs.
upgrade:
- |
The :class:`~qiskit.circuit.library.U3Gate` definition has been changed to
be in terms of the :class:`~qiskit.circuit.library.UGate` class. The
:class:`~qiskit.circuit.library.UGate` class has no definition. It is
therefore not possible to unroll **every** circuit in terms of U3
and CX anymore. Instead, U and CX can be used for **every** circuit.