Improve the effect of the anc_detectors argument (#106)

surface_sim/circuit_blocks/rot_surface_code_xzzx_google.py

@@ -100,9 +100,12 @@ def qec_round_with_log_meas(
 
     stab_type = "x_type" if rot_basis else "z_type"
     stabs = layout.get_qubits(role="anc", stab_type=stab_type)
-    stabs = [s for s in stabs if s in anc_detectors]
     detectors_stim = detectors.build_from_data(
-        model.meas_target, layout.adjacency_matrix(), anc_reset=True, anc_qubits=stabs
+        model.meas_target,
+        layout.adjacency_matrix(),
+        anc_reset=True,
+        reconstructable_stabs=stabs,
+        anc_qubits=anc_detectors,
     )
     circuit += detectors_stim
 

surface_sim/circuit_blocks/util.py

@@ -76,9 +76,12 @@ def log_meas(
     # detectors and logical observables
     stab_type = "x_type" if rot_basis else "z_type"
     stabs = layout.get_qubits(role="anc", stab_type=stab_type)
-    stabs = [s for s in stabs if s in anc_detectors]
     detectors_stim = detectors.build_from_data(
-        model.meas_target, layout.adjacency_matrix(), anc_reset, anc_qubits=stabs
+        model.meas_target,
+        layout.adjacency_matrix(),
+        anc_reset,
+        reconstructable_stabs=stabs,
+        anc_qubits=anc_detectors,
     )
     circuit += detectors_stim
 
@@ -313,9 +316,12 @@ def log_meas_xzzx(
     # detectors and logical observables
     stab_type = "x_type" if rot_basis else "z_type"
     stabs = layout.get_qubits(role="anc", stab_type=stab_type)
-    stabs = [s for s in stabs if s in anc_detectors]
     detectors_stim = detectors.build_from_data(
-        model.meas_target, layout.adjacency_matrix(), anc_reset, anc_qubits=stabs
+        model.meas_target,
+        layout.adjacency_matrix(),
+        anc_reset,
+        reconstructable_stabs=stabs,
+        anc_qubits=anc_detectors,
     )
     circuit += detectors_stim
 

surface_sim/detectors/detectors.py

@@ -1,4 +1,4 @@
-from collections.abc import Callable
+from collections.abc import Callable, Iterable
 from copy import deepcopy
 
 import numpy as np
@@ -11,7 +11,7 @@
 
 
 class Detectors:
-    def __init__(self, anc_qubits: list[str], frame: str) -> None:
+    def __init__(self, anc_qubits: Iterable[str], frame: str) -> None:
         """Initalises the ``Detectors`` class.
 
         Parameters
@@ -34,6 +34,13 @@ def __init__(self, anc_qubits: list[str], frame: str) -> None:
         Detector frame ``'r-1'`` build the detectors in the basis given by the
         stabilizer generators of the previous-last-measured QEC round.
         """
+        if not isinstance(anc_qubits, Iterable):
+            raise TypeError(
+                f"'anc_qubits' must be iterable, but {type(anc_qubits)} was given."
+            )
+        if not isinstance(frame, str):
+            raise TypeError(f"'frame' must be a str, but {type(frame)} was given.")
+
         self.anc_qubits = anc_qubits
         self.frame = frame
 
@@ -121,7 +128,7 @@ def build_from_anc(
         self,
         get_rec: Callable,
         anc_reset: bool,
-        anc_qubits: list[str] | None = None,
+        anc_qubits: Iterable[str] | None = None,
     ) -> stim.Circuit:
         """Returns the stim circuit with the corresponding detectors
         given that the ancilla qubits have been measured.
@@ -143,6 +150,15 @@ def build_from_anc(
         detectors_stim
             Detectors defined in a ``stim`` circuit.
         """
+        if not (isinstance(anc_qubits, Iterable) or (anc_qubits is None)):
+            raise TypeError(
+                f"'anc_qubits' must be iterable or None, but {type(anc_qubits)} was given."
+            )
+        if not isinstance(get_rec, Callable):
+            raise TypeError(
+                f"'get_rec' must be callable, but {type(get_rec)} was given."
+            )
+
         if self.frame == "1":
             basis = self.init_gen
         elif self.frame == "r":
@@ -154,6 +170,9 @@ def build_from_anc(
                 f"'frame' must be '1', 'r-1', or 'r', but {self.frame} was given."
             )
 
+        if anc_qubits is None:
+            anc_qubits = self.curr_gen.stab_gen.values.tolist()
+
         self.num_rounds += 1
 
         detectors = _get_ancilla_meas_for_detectors(
@@ -164,13 +183,15 @@ def build_from_anc(
             anc_reset_curr=anc_reset,
             anc_reset_prev=anc_reset,
         )
-        if anc_qubits is not None:
-            detectors = {anc: d for anc, d in detectors.items() if anc in anc_qubits}
 
         # build the stim circuit
         detectors_stim = stim.Circuit()
-        for targets in detectors.values():
-            detectors_rec = [get_rec(*t) for t in targets]
+        for anc, targets in detectors.items():
+            if anc in anc_qubits:
+                detectors_rec = [get_rec(*t) for t in targets]
+            else:
+                # create the detector but make it be always 0
+                detectors_rec = []
             detectors_stim.append("DETECTOR", detectors_rec, [])
 
         # update generators
@@ -183,7 +204,8 @@ def build_from_data(
         get_rec: Callable,
         adjacency_matrix: xr.DataArray,
         anc_reset: bool,
-        anc_qubits: list[str] | None = None,
+        reconstructable_stabs: Iterable[str],
+        anc_qubits: Iterable[str] | None = None,
     ) -> stim.Circuit:
         """Returns the stim circuit with the corresponding detectors
         given that the data qubits have been measured.
@@ -200,6 +222,8 @@ def build_from_data(
             See ``qec_util.Layout.adjacency_matrix`` for more information.
         anc_reset
             Flag for if the ancillas are being reset in every QEC cycle.
+        reconstructable_stabs
+            Stabilizers that can be reconstructed from the data qubit outcomes.
         anc_qubits
             List of the ancilla qubits for which to build the detectors.
             By default, builds all the detectors.
@@ -209,6 +233,20 @@ def build_from_data(
         detectors_stim
             Detectors defined in a ``stim`` circuit.
         """
+        if not isinstance(reconstructable_stabs, Iterable):
+            raise TypeError(
+                "'reconstructable_stabs' must be iterable, "
+                f"but {type(reconstructable_stabs)} was given."
+            )
+        if not (isinstance(anc_qubits, Iterable) or (anc_qubits is None)):
+            raise TypeError(
+                f"'anc_qubits' must be iterable or None, but {type(anc_qubits)} was given."
+            )
+        if not isinstance(get_rec, Callable):
+            raise TypeError(
+                f"'get_rec' must be callable, but {type(get_rec)} was given."
+            )
+
         if self.frame == "1":
             basis = self.init_gen
         elif self.frame == "r":
@@ -220,6 +258,9 @@ def build_from_data(
                 f"'frame' must be '1', 'r-1', or 'r', but {self.frame} was given."
             )
 
+        if anc_qubits is None:
+            anc_qubits = self.curr_gen.stab_gen.values.tolist()
+
         self.num_rounds += 1
 
         anc_detectors = _get_ancilla_meas_for_detectors(
@@ -230,10 +271,9 @@ def build_from_data(
             anc_reset_curr=True,
             anc_reset_prev=anc_reset,
         )
-        if anc_qubits is not None:
-            anc_detectors = {
-                anc: d for anc, d in anc_detectors.items() if anc in anc_qubits
-            }
+        anc_detectors = {
+            anc: d for anc, d in anc_detectors.items() if anc in reconstructable_stabs
+        }
 
         # udpate the (anc, -1) to a the corresponding set of (data, -1)
         detectors = {}
@@ -257,8 +297,12 @@ def build_from_data(
 
         # build the stim circuit
         detectors_stim = stim.Circuit()
-        for targets in detectors.values():
-            detectors_rec = [get_rec(*t) for t in targets]
+        for anc, targets in detectors.items():
+            if anc in anc_qubits:
+                detectors_rec = [get_rec(*t) for t in targets]
+            else:
+                # create the detector but make it be always 0
+                detectors_rec = []
             detectors_stim.append("DETECTOR", detectors_rec, [])
 
         # update generators

tests/detectors/test_detectors.py

@@ -62,6 +62,7 @@ def test_detectors_update():
             data=np.identity(2),
             coords=dict(from_qubit=["X1", "Z1"], to_qubit=["D1", "D2"]),
         ),
+        reconstructable_stabs=anc_qubits,
     )
     assert (detectors.curr_gen == new_gen).all()
     assert (detectors.prev_gen == new_gen).all()
@@ -270,7 +271,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="1")
     detectors.num_rounds = 0
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=True)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=True, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -280,7 +283,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="1")
     detectors.num_rounds = 1
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=True)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=True, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -290,7 +295,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="1")
     detectors.num_rounds = 1
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=False)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=False, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -300,7 +307,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="1")
     detectors.num_rounds = 2
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=False)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=False, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -333,7 +342,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r")
     detectors.num_rounds = 0
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=True)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=True, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -343,7 +354,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r")
     detectors.num_rounds = 1
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=True)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=True, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -353,7 +366,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r")
     detectors.num_rounds = 1
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=False)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=False, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -363,7 +378,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r")
     detectors.num_rounds = 2
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=False)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=False, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -396,7 +413,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r-1")
     detectors.num_rounds = 0
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=True)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=True, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -406,7 +425,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r-1")
     detectors.num_rounds = 1
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=True)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=True, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -416,7 +437,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r-1")
     detectors.num_rounds = 1
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=False)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=False, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]
@@ -426,7 +449,9 @@ def meas_rec(q, t):
     detectors = Detectors(anc_qubits=anc_qubits, frame="r-1")
     detectors.num_rounds = 2
     detectors.update(unitary_mat)
-    detectors_stim = detectors.build_from_data(meas_rec, adj_matrix, anc_reset=False)
+    detectors_stim = detectors.build_from_data(
+        meas_rec, adj_matrix, anc_reset=False, reconstructable_stabs=anc_qubits
+    )
     detector_rec = [
         sorted([t.value for t in instr.targets_copy()]) for instr in detectors_stim
     ]

tests/experiments/test_rot_surface_code_css.py

@@ -77,7 +77,16 @@ def test_memory_experiment_anc_detectors():
         rot_basis=True,
     )
 
-    assert circuit.num_detectors == 10 + 1
+    num_anc = len(layout.get_qubits(role="anc"))
+    num_anc_x = len(layout.get_qubits(role="anc", stab_type="x_type"))
+    assert circuit.num_detectors == 10 * num_anc + num_anc_x
+
+    non_zero_dets = []
+    for instr in circuit.flattened():
+        if instr.name == "DETECTOR" and len(instr.targets_copy()) != 0:
+            non_zero_dets.append(instr)
+
+    assert len(non_zero_dets) == 10 + 1
 
     return
 
@@ -100,6 +109,15 @@ def test_repeated_s_experiment_anc_detectors():
         rot_basis=True,
     )
 
-    assert circuit.num_detectors == 1 + 4 * 2 + 1
+    num_anc = len(layout.get_qubits(role="anc"))
+    num_anc_x = len(layout.get_qubits(role="anc", stab_type="x_type"))
+    assert circuit.num_detectors == (1 + 4 * 2) * num_anc + num_anc_x
+
+    non_zero_dets = []
+    for instr in circuit.flattened():
+        if instr.name == "DETECTOR" and len(instr.targets_copy()) != 0:
+            non_zero_dets.append(instr)
+
+    assert len(non_zero_dets) == 1 + 4 * 2 + 1
 
     return