Merge pull request #1076 from qiboteam/fix_backend

Handling global backend for protocols involving circuits

Author: andrea-pasquale

src/qibocal/auto/execute.py

@@ -104,11 +104,7 @@ def create(cls, name: str, platform: Union[Platform, str, None] = None):
         platform = (
             platform
             if isinstance(platform, Platform)
-            else create_platform(
-                platform
-                if platform is not None
-                else os.environ.get("QIBO_PLATFORM", "dummy")
-            )
+            else create_platform(platform if platform is not None else "dummy")
         )
         return cls(
             name=name,

src/qibocal/auto/runcard.py

@@ -1,6 +1,5 @@
 """Specify runcard layout, handles (de)serialization."""
 
-import os
 from dataclasses import asdict
 from pathlib import Path
 from typing import Any, Optional, Union
@@ -33,7 +32,7 @@ class Runcard:
     """
     backend: str = "qibolab"
     """Qibo backend."""
-    platform: str = os.environ.get("QIBO_PLATFORM", "dummy")
+    platform: str = "dummy"
     """Qibolab platform."""
     update: bool = True
 

src/qibocal/auto/transpile.py

@@ -1,7 +1,7 @@
 from typing import Optional
 
 from qibo import Circuit
-from qibo.backends.abstract import Backend
+from qibo.backends import Backend
 from qibo.transpiler.pipeline import Passes
 from qibo.transpiler.unroller import NativeGates, Unroller
 from qibolab.qubits import QubitId
@@ -28,20 +28,18 @@ def transpile_circuits(
         are all string or all integers.
     """
     transpiled_circuits = []
-
-    qubits = list(backend.platform.qubits)
+    platform = backend.platform
+    qubits = list(platform.qubits)
     if isinstance(qubit_maps[0][0], str):
         for i, qubit_map in enumerate(qubit_maps):
             qubit_map = map(lambda x: qubits.index(x), qubit_map)
             qubit_maps[i] = list(qubit_map)
-    if backend.name == "qibolab":
-        platform_nqubits = backend.platform.nqubits
-        for circuit, qubit_map in zip(circuits, qubit_maps):
-            new_circuit = pad_circuit(platform_nqubits, circuit, qubit_map)
-            transpiled_circ, _ = transpiler(new_circuit)
-            transpiled_circuits.append(transpiled_circ)
-    else:
-        transpiled_circuits = circuits
+    platform_nqubits = platform.nqubits
+    for circuit, qubit_map in zip(circuits, qubit_maps):
+        new_circuit = pad_circuit(platform_nqubits, circuit, qubit_map)
+        transpiled_circ, _ = transpiler(new_circuit)
+        transpiled_circuits.append(transpiled_circ)
+
     return transpiled_circuits
 
 
@@ -99,20 +97,19 @@ def execute_transpiled_circuit(
         backend,
         transpiler,
     )[0]
+
     return transpiled_circ, backend.execute_circuit(
         transpiled_circ, initial_state=initial_state, nshots=nshots
     )
 
 
-def dummy_transpiler(backend) -> Optional[Passes]:
+def dummy_transpiler(backend: Backend) -> Passes:
     """
     If the backend is `qibolab`, a transpiler with just an unroller is returned,
     otherwise None.
     """
-    if backend.name == "qibolab":
-        unroller = Unroller(NativeGates.default())
-        return Passes(connectivity=backend.platform.topology, passes=[unroller])
-    return None
+    unroller = Unroller(NativeGates.default())
+    return Passes(connectivity=backend.platform.topology, passes=[unroller])
 
 
 def pad_circuit(nqubits, circuit: Circuit, qubit_map: list[int]) -> Circuit:

src/qibocal/protocols/randomized_benchmarking/noisemodels.py

@@ -1,4 +1,4 @@
-from dataclasses import dataclass, field
+from dataclasses import dataclass
 from typing import Iterable, Optional, TypedDict, Union
 
 import numpy as np
@@ -52,12 +52,6 @@ class StandardRBParameters(Parameters):
     If ``None``, uses a random seed.
     Defaults is ``None``.
     """
-    noise_model: Optional[str] = None
-    """For simulation purposes, string has to match what is in
-    :mod:`qibocal.protocols.randomized_benchmarking.noisemodels`"""
-    noise_params: Optional[list] = field(default_factory=list)
-    """With this the noise model will be initialized, if not given random
-    values will be used."""
     nshots: int = 10
     """Just to add the default value."""
 

src/qibocal/protocols/randomized_benchmarking/standard_rb.py

@@ -7,8 +7,7 @@
 import numpy as np
 import numpy.typing as npt
 from qibo import gates
-from qibo.backends import get_backend
-from qibo.config import raise_error
+from qibo.backends import construct_backend
 from qibo.models import Circuit
 from qibolab.platform import Platform
 from qibolab.qubits import QubitId, QubitPairId
@@ -19,8 +18,6 @@
     execute_transpiled_circuit,
     execute_transpiled_circuits,
 )
-from qibocal.config import raise_error
-from qibocal.protocols.randomized_benchmarking import noisemodels
 from qibocal.protocols.randomized_benchmarking.dict_utils import (
     SINGLE_QUBIT_CLIFFORDS_NAMES,
     calculate_pulses_clifford,
@@ -118,7 +115,6 @@ def random_circuits(
     targets: list[Union[QubitId, QubitPairId]],
     niter,
     rb_gen,
-    noise_model=None,
     inverse_layer=True,
     single_qubit=True,
     file_inv=pathlib.Path(),
@@ -134,8 +130,6 @@ def random_circuits(
             if inverse_layer:
                 add_inverse_layer(circuit, rb_gen, single_qubit, file_inv)
             add_measurement_layer(circuit)
-            if noise_model is not None:
-                circuit = noise_model.apply(circuit)
             circuits.append(circuit)
             indexes[target].append(random_index)
 
@@ -341,30 +335,17 @@ def setup(
     interleave: Optional[str] = None,
 ):
     """
-    Set up the randomized benchmarking experiment backend, noise model and data class.
+    Set up the randomized benchmarking experiment backend and data class.
 
     Args:
         params (Parameters): The parameters for the experiment.
         single_qubit (bool, optional): Flag indicating whether the experiment is for a single qubit or two qubits. Defaults to True.
         interleave: (str, optional): The type of interleaving to apply. Defaults to None.
 
     Returns:
-        tuple: A tuple containing the experiment data, noise model, and backend.
+        tuple: A tuple containing the experiment data and backend.
     """
-
-    backend = get_backend()
-    backend.platform = platform
-    # For simulations, a noise model can be added.
-    noise_model = None
-    if params.noise_model is not None:
-        if backend.name == "qibolab":
-            raise_error(
-                ValueError,
-                "Backend qibolab (%s) does not perform noise models simulation. ",
-            )
-
-        noise_model = getattr(noisemodels, params.noise_model)(params.noise_params)
-        params.noise_params = noise_model.params.tolist()
+    backend = construct_backend(backend="qibolab", platform=platform)
     # Set up the scan (here an iterator of circuits of random clifford gates with an inverse).
     if single_qubit:
         cls = RBData
@@ -380,12 +361,10 @@ def setup(
         niter=params.niter,
     )
 
-    return data, noise_model, backend
+    return data, backend
 
 
-def get_circuits(
-    params, targets, add_inverse_layer, interleave, noise_model, single_qubit=True
-):
+def get_circuits(params, targets, add_inverse_layer, interleave, single_qubit=True):
     """
     Generate randomized benchmarking circuits.
 
@@ -394,7 +373,6 @@ def get_circuits(
         targets (list): List of target qubit IDs.
         add_inverse_layer (bool): Flag indicating whether to add an inverse layer to the circuits.
         interleave (str): String indicating whether to interleave the circuits with the given gate.
-        noise_model (str): Noise model string.
         single_qubit (bool, optional): Flag indicating whether to generate single qubit circuits.
 
     Returns:
@@ -421,7 +399,6 @@ def get_circuits(
             qubits_ids,
             params.niter,
             rb_gen,
-            noise_model,
             add_inverse_layer,
             single_qubit,
             inv_file,
@@ -455,6 +432,7 @@ def execute_circuits(circuits, targets, params, backend, single_qubit=True):
 
     """
     # Execute the circuits
+    platform = backend.platform
     transpiler = dummy_transpiler(backend)
     qubit_maps = (
         [[i] for i in targets] * (len(params.depths) * params.niter)
@@ -503,9 +481,9 @@ def rb_acquisition(
     Returns:
         RBData: The depths, samples, and ground state probability of each experiment in the scan.
     """
-    data, noise_model, backend = setup(params, platform, single_qubit=True)
+    data, backend = setup(params, platform, single_qubit=True)
     circuits, indexes, npulses_per_clifford = get_circuits(
-        params, targets, add_inverse_layer, interleave, noise_model, single_qubit=True
+        params, targets, add_inverse_layer, interleave, single_qubit=True
     )
     executed_circuits = execute_circuits(circuits, targets, params, backend)
 
@@ -549,10 +527,10 @@ def twoq_rb_acquisition(
     Returns:
         RB2QData: The acquired data for two qubit randomized benchmarking.
     """
-
-    data, noise_model, backend = setup(params, platform, single_qubit=False)
+    targets = [tuple(pair) if isinstance(pair, list) else pair for pair in targets]
+    data, backend = setup(params, platform, single_qubit=False)
     circuits, indexes, npulses_per_clifford = get_circuits(
-        params, targets, add_inverse_layer, interleave, noise_model, single_qubit=False
+        params, targets, add_inverse_layer, interleave, single_qubit=False
     )
     executed_circuits = execute_circuits(
         circuits, targets, params, backend, single_qubit=False

src/qibocal/protocols/randomized_benchmarking/utils.py

@@ -5,7 +5,7 @@
 import numpy.typing as npt
 import plotly.express as px
 from qibo import gates
-from qibo.backends import get_backend
+from qibo.backends import construct_backend
 from qibo.models import Circuit
 from qibolab.platform import Platform
 from qibolab.qubits import QubitId
@@ -61,8 +61,7 @@ def _acquisition(
     data = ReadoutMitigationMatrixData(
         nshots=params.nshots, qubit_list=[list(qq) for qq in targets]
     )
-    backend = get_backend()
-    backend.platform = platform
+    backend = construct_backend("qibolab", platform=platform)
     transpiler = dummy_transpiler(backend)
     qubit_map = [i for i in range(platform.nqubits)]
     for qubits in targets:
@@ -125,25 +124,30 @@ def _plot(
     fitting_report = ""
     figs = []
     if fit is not None:
-        computational_basis = [
-            format(i, f"0{len(target)}b") for i in range(2 ** len(target))
-        ]
-        measurement_matrix = np.linalg.inv(fit.readout_mitigation_matrix[tuple(target)])
-        z = measurement_matrix
-        fig = px.imshow(
-            z,
-            x=computational_basis,
-            y=computational_basis,
-            text_auto=True,
-            labels={
-                "x": "Prepeared States",
-                "y": "Measured States",
-                "color": "Probabilities",
-            },
-            width=700,
-            height=700,
-        )
-        figs.append(fig)
+        if tuple(target) in fit.readout_mitigation_matrix:
+            computational_basis = [
+                format(i, f"0{len(target)}b") for i in range(2 ** len(target))
+            ]
+            # use pinv since it should be already invertibile
+            # however when casting to list we could lose precision
+            measurement_matrix = np.linalg.pinv(
+                fit.readout_mitigation_matrix[tuple(target)]
+            )
+            z = measurement_matrix
+            fig = px.imshow(
+                z,
+                x=computational_basis,
+                y=computational_basis,
+                text_auto=True,
+                labels={
+                    "x": "Prepeared States",
+                    "y": "Measured States",
+                    "color": "Probabilities",
+                },
+                width=700,
+                height=700,
+            )
+            figs.append(fig)
     return figs, fitting_report
 
 

src/qibocal/protocols/readout_mitigation_matrix.py

@@ -8,7 +8,7 @@
 import plotly.graph_objects as go
 from plotly.subplots import make_subplots
 from qibo import Circuit, gates
-from qibo.backends import NumpyBackend, get_backend, matrices
+from qibo.backends import NumpyBackend, construct_backend, matrices
 from qibo.quantum_info import fidelity, partial_trace
 from qibolab.platform import Platform
 from qibolab.qubits import QubitId
@@ -102,8 +102,7 @@ def _acquisition(
     if params.circuit is None:
         params.circuit = Circuit(len(targets))
 
-    backend = get_backend()
-    backend.platform = platform
+    backend = construct_backend("qibolab", platform=platform)
     transpiler = dummy_transpiler(backend)
 
     data = StateTomographyData(