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Handle PrimitiveResult as result type #340

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merged 2 commits into from
May 29, 2024
Merged

Handle PrimitiveResult as result type #340

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84f7d59
Handle PrimitiveResult as result type.
cqc-alec May 24, 2024
618973b
Flatten bits to default register before conversion.
cqc-alec May 29, 2024
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37 changes: 28 additions & 9 deletions pytket/extensions/qiskit/backends/ibm.py
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Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,9 @@
)
from warnings import warn

from qiskit.primitives import SamplerResult # type: ignore
import numpy as np

from qiskit.primitives import PrimitiveResult, SamplerResult # type: ignore


# RuntimeJob has no queue_position attribute, which is referenced
Expand All @@ -48,7 +50,7 @@
RuntimeJob,
)

from pytket.circuit import Circuit, OpType
from pytket.circuit import Bit, Circuit, OpType
from pytket.backends import Backend, CircuitNotRunError, CircuitStatus, ResultHandle
from pytket.backends.backendinfo import BackendInfo
from pytket.backends.backendresult import BackendResult
Expand Down Expand Up @@ -138,6 +140,12 @@ def _get_primitive_gates(gateset: Set[OpType]) -> Set[OpType]:
return gateset


def _int_from_readout(readout: np.ndarray) -> int:
# Weird mixture of big- and little-endian here.
n_bytes = len(readout)
return sum(int(x) << (8 * (n_bytes - 1 - i)) for i, x in enumerate(readout))


class IBMQBackend(Backend):
"""A backend for running circuits on remote IBMQ devices.

Expand Down Expand Up @@ -525,11 +533,14 @@ def process_circuits(

qcs, ppcirc_strs = [], []
for tkc in batch_chunk:
tkc1 = tkc.copy()
# Flatten bits to default register in lexicographic order:
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This solves the issue raised in this comment. There is still an issue with circuits having non-default classical register names, but this is an independent pre-existing issue and is not addressed in this PR.

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Just to make sure I understand: this does actually all work if pytket-qiskit is used to submit and retrieve the circuit no matter what the classical registers are named. Of course if one separately submits a circuit with non-default classical register names and tries to retrieve it with pytket-qiskit then there is an error... but that is indeed a different issue!

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Yes, it works unless you then want to call get_counts() on the result with specific bits, using the cbits parameter to get_counts. In that case it will throw an error -- but that was already the case (separate issue).

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Thanks that makes sense!

tkc1.rename_units({bit: Bit(i) for i, bit in enumerate(tkc1.bits)})
if postprocess:
c0, ppcirc = prepare_circuit(tkc, allow_classical=False)
c0, ppcirc = prepare_circuit(tkc1, allow_classical=False)
ppcirc_rep = ppcirc.to_dict()
else:
c0, ppcirc_rep = tkc, None
c0, ppcirc_rep = tkc1, None
if simplify_initial:
SimplifyInitial(
allow_classical=False, create_all_qubits=True
Expand Down Expand Up @@ -614,11 +625,19 @@ def get_result(self, handle: ResultHandle, **kwargs: KwargTypes) -> BackendResul
sleep(10)

res = job.result(timeout=kwargs.get("timeout", None))
assert isinstance(res, SamplerResult)
for circ_index, (r, d) in enumerate(zip(res.quasi_dists, res.metadata)):
self._ibm_res_cache[(jobid, circ_index)] = Counter(
{n: int(0.5 + d["shots"] * p) for n, p in r.items()}
)
if isinstance(res, SamplerResult):
# TODO Is this code still reachable?
for circ_index, (r, d) in enumerate(zip(res.quasi_dists, res.metadata)):
self._ibm_res_cache[(jobid, circ_index)] = Counter(
{n: int(0.5 + d["shots"] * p) for n, p in r.items()}
)
else:
assert isinstance(res, PrimitiveResult)
for circ_index, pub_result in enumerate(res._pub_results):
readouts = pub_result.data.c.array
self._ibm_res_cache[(jobid, circ_index)] = Counter(
_int_from_readout(readout) for readout in readouts
)

counts = self._ibm_res_cache[cache_key] # Counter[int]
# Convert to `OutcomeArray`:
Expand Down