Narrow QPY 18 SPARSE_OBSERVABLE bit terms from uint16_t to uint8_t - #16800
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… bytes to 1 byte Signed-off-by: mohamedmahameed <mohamed.mahameed@ibm.com>
Signed-off-by: mohamedmahameed <mohamed.mahameed@ibm.com>
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| /// representation is always `u8` and this parser absorbs the difference, so nothing downstream has | ||
| /// to care which version produced the payload. | ||
| #[binrw::parser(reader, endian)] | ||
| fn read_bitterms(version: u8, count: u64) -> BinResult<Vec<u8>> { |
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Good way to deal with this.
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| let data = match gate_type { | ||
| CircuitInstructionType::PauliEvolutionGate => Some(serialize( | ||
| // The evolution payload needs the target QPY version: the width of the observable's bit |
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No need to elaborate on this here.
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removed unnecessary comment
Signed-off-by: mohamedmahameed <mohamed.mahameed@ibm.com>
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Summary
QPY 18 now stores the bit terms of a
SPARSE_OBSERVABLEpayload as (uint8_t) instead of (uint16_t).SparseObservableoperators is now one byte smaller per bit term, with no loss of information.The change is backwards compatible: v17 and earlier payloads load exactly as before, and
qpy.dump(..., version=17)still emits the older encoding.Tests
test/python/qpy/test_v18.py::TestV18SparseObservablecovers an evolution gate whose observableuses every
BitTermvariant and one over a mixedSparseObservable/SparsePauliOplist, eachround-tripped at v17 and v18 so both widths are exercised.
Note
This PR also depends on the bug fix PR: #16788
After merging the fix more test cases can be added.
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