bit

example/grover.py

@@ -3,13 +3,13 @@
 
 def oracle(v, target):
     n = q.num_qubits(v)
-    for i in range(n):
-        if (target >> (n - i - 1)) & 1 == 0:
-            v = q.apply(v, q.op.x(), [i])
+    for k in range(n):
+        if q.util.bit(n, target, k) == 0:
+            v = q.apply(v, q.op.x(), [k])
     v = q.apply_seq(v, q.op.controlled_seq(q.op.z(), list(range(n))))
-    for i in range(n):
-        if (target >> (n - i - 1)) & 1 == 0:
-            v = q.apply(v, q.op.x(), [i])
+    for k in range(n):
+        if q.util.bit(n, target, k) == 0:
+            v = q.apply(v, q.op.x(), [k])
     return v
 
 

src/qailo/util/__init__.py

@@ -1,3 +1,3 @@
-from .strops import binary2str, str2binary
+from .bitops import binary2str, bit, str2binary
 
-__all__ = [binary2str, str2binary]
+__all__ = [binary2str, bit, str2binary]

src/qailo/util/strops.py → src/qailo/util/bitops.py

@@ -1,3 +1,8 @@
+def bit(n, s, k):
+    """extract k-th bit from integer s"""
+    return (s >> (n - k - 1)) & 1
+
+
 def binary2str(n, i):
     return bin(i)[2:].zfill(n)[::-1]
 

test/util/test_binary2str.py

@@ -1,4 +1,4 @@
-from qailo.util.strops import binary2str, str2binary
+from qailo.util.bitops import binary2str, str2binary
 
 
 def test_binary2str():

test/util/test_bit.py

@@ -0,0 +1,7 @@
+from qailo.util.bitops import bit
+
+
+def test_bit():
+    assert bit(3, 0b100, 0) == 1
+    assert bit(3, 0b100, 1) == 0
+    assert bit(3, 0b100, 2) == 0