remove letters and replace

src/qailo/operator/multiply.py

@@ -1,6 +1,5 @@
 import numpy as np
 
-from ..util.strops import letters, replace
 from .type import is_operator, num_qubits
 
 
@@ -16,9 +15,10 @@ def multiply(pin, p, pos=None):
     for i in pos:
         assert i < n
 
-    ss_opi = ss_to = letters()[: 2 * n]
-    ss_op = letters()[2 * n : 2 * n + 2 * m]
+    ss_pin = list(range(2 * n))
+    ss_p = list(range(2 * n, 2 * n + 2 * m))
+    ss_to = list(range(2 * n))
     for i in range(m):
-        ss_opi = replace(ss_opi, pos[i], ss_op[m + i])
-        ss_to = replace(ss_to, pos[i], ss_op[i])
-    return np.einsum("{},{}->{}".format(ss_opi, ss_op, ss_to), pin, p)
+        ss_pin[pos[i]] = ss_p[m + i]
+        ss_to[pos[i]] = ss_p[i]
+    return np.einsum(pin, ss_pin, p, ss_p, ss_to)

src/qailo/operator/trace.py

@@ -1,6 +1,5 @@
 import numpy as np
 
-from ..util.strops import letters, replace
 from .type import is_density_matrix, is_operator, num_qubits
 
 
@@ -14,7 +13,7 @@ def trace(q, pos=None):
     for i in pos:
         assert i < n
 
-    ss = letters()[: 2 * n]
+    ss = list(range(2 * n))
     for i in pos:
-        ss = replace(ss, n + i, ss[i])
-    return np.einsum(ss, q)
+        ss[n + i] = ss[i]
+    return np.einsum(q, ss)

src/qailo/state_vector/apply.py

@@ -1,7 +1,6 @@
 import numpy as np
 
 from ..operator import type as op
-from ..util.strops import letters, replace
 from . import type as sv
 
 
@@ -14,9 +13,10 @@ def apply(v, p, pos=None):
         pos = range(n)
     assert len(pos) == m
 
-    ss_op = letters()[: 2 * m]
-    ss_v = ss_to = letters()[2 * m : 2 * m + n + 1]
+    ss_v = list(range(2 * m, 2 * m + n + 1))
+    ss_op = list(range(2 * m))
+    ss_to = list(range(2 * m, 2 * m + n + 1))
     for i in range(m):
-        ss_v = replace(ss_v, pos[i], ss_op[m + i])
-        ss_to = replace(ss_to, pos[i], ss_op[i])
-    return np.einsum("{},{}->{}".format(ss_v, ss_op, ss_to), v, p)
+        ss_v[pos[i]] = ss_op[m + i]
+        ss_to[pos[i]] = ss_op[i]
+    return np.einsum(v, ss_v, p, ss_op, ss_to)

src/qailo/state_vector/pure_state.py

@@ -1,19 +1,13 @@
 import numpy as np
 
-from ..util.strops import letters
 from . import type as sv
 
 
 def pure_state(v):
     assert sv.is_state_vector(v)
     n = sv.num_qubits(v)
-    v = v / np.linalg.norm(v)
-    ss_from0 = letters()[: n + 1]
-    ss_from1 = letters()[n + 1 : 2 * n + 2]
-    ss_to = (
-        letters()[:n]
-        + letters()[n + 1 : 2 * n + 1]
-        + letters()[n]
-        + letters()[2 * n + 1]
-    )
-    return np.einsum("{},{}->{}".format(ss_from0, ss_from1, ss_to), v, v.conj())
+    w = (v / np.linalg.norm(v)).reshape((2,) * n)
+    ss0 = list(range(n))
+    ss1 = list(range(n, 2 * n))
+    shape = (2,) * (2 * n) + (1, 1)
+    return np.einsum(w, ss0, w.conj(), ss1).reshape(shape)

src/qailo/util/strops.py

@@ -1,21 +1,7 @@
-import string
-
-
 def binary2str(n, i):
     return bin(i)[2:].zfill(n)
 
 
-def letters():
-    return string.ascii_lowercase + string.ascii_uppercase
-
-
-def replace(s, i, c):
-    if i < 0:
-        i += len(s)
-
-    return s[:i] + c + s[i + 1 :]
-
-
 def str2binary(s):
     n = len(s)
     c = 0