mirror of https://github.com/Qiskit/qiskit.git
28 lines
1.7 KiB
YAML
28 lines
1.7 KiB
YAML
---
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features_circuits:
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Construction time for :class:`.QuantumVolume` circuits has been significantly improved, on the
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order of 10x or a bit more. The internal SU4 gates will now also use more bits of randomness
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during their generation, leading to more representative volume circuits, especially at large
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widths and depths.
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:class:`.QuantumVolume` now has a ``flatten`` keyword argument. This defaults to ``False``,
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where the constructed circuit contains a single instruction that in turn contains the actual
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volume structure. If set ``True``, the circuit will directly have the volumetric SU4 matrices.
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:class:`.UnitaryGate` now accepts an optional ``num_qubits`` argument. The only effect of this
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is to skip the inference of the qubit count, which can be helpful for performance when many
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gates are being constructed.
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upgrade_circuits:
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The random-number usage of :class:`.QuantumVolume` has changed, so you will get a different
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circuit for a fixed seed between older versions of Qiskit and this version. The random-unitary
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generation now uses more bits of entropy, so large circuits will be less biased.
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The internal :class:`.UnitaryGate` instances in the definition of a :class:`.QuantumVolume`
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circuit will no longer have a :attr:`~.Instruction.label` field set. Previously this was set
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to the string ``su4_<seed>`` where ``<seed>`` was a three-digit number denoting the seed of an
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internal Numpy pRNG instance for that gate. Doing this was a serious performance problem, and
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the seed ought not to have been useful; if you need to retrieve the matrix from the gate, simply
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use the :meth:`.Gate.to_matrix` method.
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