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Avoid lossing precision when scaling frequencies (backport #12392) #12480

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merged 2 commits into from
Jun 4, 2024
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Avoid lossing precision when scaling frequencies (backport #12392) #12480

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38af9c3
Avoid lossing precision when scaling frequencies (#12392)
iyanmv May 16, 2024
41694e8
Merge branch 'stable/0.46' into mergify/bp/stable/0.46/pr-12392
1ucian0 Jun 4, 2024
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12 changes: 6 additions & 6 deletions qiskit/qobj/converters/pulse_instruction.py
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Original file line number Diff line number Diff line change
Expand Up @@ -243,7 +243,7 @@ def _convert_set_frequency(
"name": "setf",
"t0": time_offset + instruction.start_time,
"ch": instruction.channel.name,
"frequency": instruction.frequency / 1e9,
"frequency": instruction.frequency / 10**9,
}
return self._qobj_model(**command_dict)

Expand All @@ -266,7 +266,7 @@ def _convert_shift_frequency(
"name": "shiftf",
"t0": time_offset + instruction.start_time,
"ch": instruction.channel.name,
"frequency": instruction.frequency / 1e9,
"frequency": instruction.frequency / 10**9,
}
return self._qobj_model(**command_dict)

Expand Down Expand Up @@ -836,7 +836,7 @@ def _convert_setf(
.. note::

We assume frequency value is expressed in string with "GHz".
Operand value is thus scaled by a factor of 1e9.
Operand value is thus scaled by a factor of 10^9.

Args:
instruction: SetFrequency qobj instruction
Expand All @@ -845,7 +845,7 @@ def _convert_setf(
Qiskit Pulse set frequency instructions
"""
channel = self.get_channel(instruction.ch)
frequency = self.disassemble_value(instruction.frequency) * 1e9
frequency = self.disassemble_value(instruction.frequency) * 10**9

yield instructions.SetFrequency(frequency, channel)

Expand All @@ -858,7 +858,7 @@ def _convert_shiftf(
.. note::

We assume frequency value is expressed in string with "GHz".
Operand value is thus scaled by a factor of 1e9.
Operand value is thus scaled by a factor of 10^9.

Args:
instruction: ShiftFrequency qobj instruction
Expand All @@ -867,7 +867,7 @@ def _convert_shiftf(
Qiskit Pulse shift frequency schedule instructions
"""
channel = self.get_channel(instruction.ch)
frequency = self.disassemble_value(instruction.frequency) * 1e9
frequency = self.disassemble_value(instruction.frequency) * 10**9

yield instructions.ShiftFrequency(frequency, channel)

Expand Down
8 changes: 8 additions & 0 deletions releasenotes/notes/fix-symbolic-unit-scaling-c3eb4d9be674dfd6.yaml
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@@ -0,0 +1,8 @@
---
fixes:
- |
Fixed a floating-point imprecision when scaling certain pulse units
between seconds and nanoseconds. If the pulse was symbolically defined,
an unnecessary floating-point error could be introduced by the scaling
for certain builds of ``symengine``, which could manifest in unexpected
results once the symbols were fully bound. See `#12392 <https://github.com/Qiskit/qiskit/pull/12392>`__.
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