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moved to src directory structure

This avoids problems with testing against the wrong package version

Joseph Weston authored on 30/11/2019 18:31:57
Showing 1 changed files
qsim/gate.py
History View file @ b4deccc
1 1 
deleted file mode 100644
... ... 
@@ -1,172 +0,0 @@
1 
-"""Quantum gate operations
2 
-
3 
-A quantum gate acting on :math:`n` qubits is a :math:`2^n×2^n` unitary
4 
-matrix written in the computational basis.
5 
-"""
6 
-
7 
-import numpy as np
8 
-
9 
-__all__ = [
10 
-    "apply",
11 
-    "n_qubits",
12 
-    "controlled",
13 
-    # -- Single qubit gates --
14 
-    "id",
15 
-    "x",
16 
-    "y",
17 
-    "z",
18 
-    "not_",
19 
-    "sqrt_not",
20 
-    "phase_shift",
21 
-    # -- 2 qubit gates --
22 
-    "cnot",
23 
-    "swap",
24 
-    # -- 3 qubit gates --
25 
-    "toffoli",
26 
-    "cswap",
27 
-    "fredkin",
28 
-    "deutsch",
29 
-]  # type: ignore
30 
-
31 
-
32 
-def apply(gate, qubits, state):
33 
-    """Apply a gate to the specified qubits of a state
34 
-
35 
-    Parameters
36 
-    ----------
37 
-    gate : ndarray[complex]
38 
-    qubits : sequence of int
39 
-        The qubits on which to act. Qubit 0 is the least significant qubit.
40 
-    state : ndarray[complex]
41 
-
42 
-    Returns
43 
-    -------
44 
-    new_state : ndarray[complex]
45 
-    """
46 
-    n_gate_qubits = gate.shape[0].bit_length() - 1
47 
-    n_state_qubits = state.shape[0].bit_length() - 1
48 
-    assert len(qubits) == n_gate_qubits
49 
-
50 
-    # We can view an n-qubit gate as a 2*n-tensor (n contravariant and n contravariant
51 
-    # indices) and an n-qubit state as an n-tensor (contravariant indices)
52 
-    # with each axis having length 2 (the state space of a single qubit).
53 
-    gate = gate.reshape((2,) * 2 * n_gate_qubits)
54 
-    state = state.reshape((2,) * n_state_qubits)
55 
-
56 
-    # Our qubits are labeled from least significant to most significant, i.e. our
57 
-    # computational basis (for e.g. 2 qubits) is ordered like |00⟩, |01⟩, |10⟩, |11⟩.
58 
-    # We represent the state as a tensor in *row-major* order; this means that the
59 
-    # axis ordering is *backwards* compared to the qubit ordering (the least significant
60 
-    # qubit corresponds to the *last* axis in the tensor etc.)
61 
-    qubit_axes = tuple(n_state_qubits - 1 - np.asarray(qubits))
62 
-
63 
-    # Applying the gate to the state vector is then the tensor product over the appropriate axes
64 
-    axes = (np.arange(n_gate_qubits, 2 * n_gate_qubits), qubit_axes)
65 
-    new_state = np.tensordot(gate, state, axes=axes)
66 
-
67 
-    # tensordot effectively re-orders the qubits such that the qubits we operated
68 
-    # on are in the most-significant positions (i.e. their axes come first). We
69 
-    # thus need to transpose the axes to place them back into their original positions.
70 
-    untouched_axes = tuple(
71 
-        idx for idx in range(n_state_qubits) if idx not in qubit_axes
72 
-    )
73 
-    inverse_permutation = np.argsort(qubit_axes + untouched_axes)
74 
-    return np.transpose(new_state, inverse_permutation).reshape(-1)
75 
-
76 
-
77 
-def _check_valid_gate(gate):
78 
-    if not (
79 
-        # is an array
80 
-        isinstance(gate, np.ndarray)
81 
-        # is complex
82 
-        and np.issubdtype(gate.dtype, np.complex128)
83 
-        # is square
84 
-        and gate.shape[0] == gate.shape[1]
85 
-        # has size 2**n, n > 1
86 
-        and np.log2(gate.shape[0]).is_integer()
87 
-        and gate.shape[0].bit_length() > 1
88 
-        # is unitary
89 
-        and np.allclose(gate @ gate.conjugate().transpose(), np.identity(gate.shape[0]))
90 
-    ):
91 
-        raise ValueError("Gate is not valid")
92 
-
93 
-
94 
-def n_qubits(gate):
95 
-    """Return the number of qubits that a gate acts on.
96 
-
97 
-    Raises ValueError if 'gate' does not have a shape that is
98 
-    an integer power of 2.
99 
-    """
100 
-    _check_valid_gate(gate)
101 
-    return gate.shape[0].bit_length() - 1
102 
-
103 
-
104 
-def controlled(gate):
105 
-    """Return a controlled quantum gate, given a quantum gate.
106 
-
107 
-    If 'gate' operates on :math:`n` qubits, then the controlled gate operates
108 
-    on :math:`n+1` qubits, where the most-significant qubit is the control.
109 
-
110 
-    Parameters
111 
-    ----------
112 
-    gate : np.ndarray[complex]
113 
-        A quantum gate acting on :math:`n` qubits;
114 
-        a :math:`2^n×2^n` unitary matrix in the computational basis.
115 
-
116 
-    Returns
117 
-    -------
118 
-    controlled_gate : np.ndarray[(2**(n+1), 2**(n+1)), complex]
119 
-    """
120 
-    _check_valid_gate(gate)
121 
-    n = gate.shape[0]
122 
-    zeros = np.zeros((n, n))
123 
-    return np.block([[np.identity(n), zeros], [zeros, gate]])
124 
-
125 
-
126 
-# -- Single qubit gates --
127 
-
128 
-#: The identity gate on 1 qubit
129 
-id = np.identity(2, complex)
130 
-#: Pauli X gate
131 
-x = np.array([[0, 1], [1, 0]], complex)
132 
-#: NOT gate
133 
-not_ = x
134 
-#: Pauli Y gate
135 
-y = np.array([[0, -1j], [1j, 0]], complex)
136 
-#: Pauli Z gate
137 
-z = np.array([[1, 0], [0, -1]], complex)
138 
-#: SQRT(NOT) gate
139 
-sqrt_not = 0.5 * (1 + 1j * id - 1j * x)
140 
-#: Hadamard gate
141 
-hadamard = np.sqrt(0.5) * (x + z)
142 
-
143 
-
144 
-def phase_shift(phi):
145 
-    "Return a gate that shifts the phase of :math:`|1⟩` by :math:`φ`."
146 
-    return np.array([[1, 0], [0, np.exp(1j * phi)]])
147 
-
148 
-
149 
-# -- Two qubit gates --
150 
-
151 
-#: Controlled NOT gate
152 
-cnot = controlled(x)
153 
-#: SWAP gate
154 
-swap = np.identity(4, complex)[:, (0, 2, 1, 3)]
155 
-
156 
-# -- Three qubit gates --
157 
-
158 
-#: Toffoli (CCNOT) gate
159 
-toffoli = controlled(cnot)
160 
-#: Controlled SWAP gate
161 
-cswap = controlled(swap)
162 
-#: Fredkin gate
163 
-fredkin = cswap
164 
-
165 
-
166 
-def deutsch(phi):
167 
-    "Return a Deutsch gate for angle :math:`φ`."
168 
-    gate = np.identity(8, complex)
169 
-    gate[-2:, -2:] = np.array(
170 
-        [[1j * np.cos(phi), np.sin(phi)], [np.sin(phi), 1j * np.cos(phi)]]
171 
-    )
172 
-    return gate
Browse code

Add docstring to qsim.gate.apply

Joseph Weston authored on 15/11/2019 21:14:53
Showing 1 changed files
qsim/gate.py
History View file @ 0232cc3
... ... 
@@ -30,6 +30,19 @@ __all__ = [
30 30
31 31
32 32 
 def apply(gate, qubits, state):
33 
+    """Apply a gate to the specified qubits of a state
34 
+
35 
+    Parameters
36 
+    ----------
37 
+    gate : ndarray[complex]
38 
+    qubits : sequence of int
39 
+        The qubits on which to act. Qubit 0 is the least significant qubit.
40 
+    state : ndarray[complex]
41 
+
42 
+    Returns
43 
+    -------
44 
+    new_state : ndarray[complex]
45 
+    """
33 46 
     n_gate_qubits = gate.shape[0].bit_length() - 1
34 47 
     n_state_qubits = state.shape[0].bit_length() - 1
35 48 
     assert len(qubits) == n_gate_qubits
Browse code

Implement application of a gate to a state.

Joseph Weston authored on 15/11/2019 20:41:21
Showing 1 changed files
qsim/gate.py
History View file @ 1673b8d
... ... 
@@ -7,6 +7,7 @@ matrix written in the computational basis.
7 7 
 import numpy as np
8 8
9 9 
 __all__ = [
10 
+    "apply",
10 11 
     "n_qubits",
11 12 
     "controlled",
12 13 
     # -- Single qubit gates --
... ... 
@@ -28,6 +29,38 @@ __all__ = [
28 29 
 ]  # type: ignore
29 30
30 31
32 
+def apply(gate, qubits, state):
33 
+    n_gate_qubits = gate.shape[0].bit_length() - 1
34 
+    n_state_qubits = state.shape[0].bit_length() - 1
35 
+    assert len(qubits) == n_gate_qubits
36 
+
37 
+    # We can view an n-qubit gate as a 2*n-tensor (n contravariant and n contravariant
38 
+    # indices) and an n-qubit state as an n-tensor (contravariant indices)
39 
+    # with each axis having length 2 (the state space of a single qubit).
40 
+    gate = gate.reshape((2,) * 2 * n_gate_qubits)
41 
+    state = state.reshape((2,) * n_state_qubits)
42 
+
43 
+    # Our qubits are labeled from least significant to most significant, i.e. our
44 
+    # computational basis (for e.g. 2 qubits) is ordered like |00⟩, |01⟩, |10⟩, |11⟩.
45 
+    # We represent the state as a tensor in *row-major* order; this means that the
46 
+    # axis ordering is *backwards* compared to the qubit ordering (the least significant
47 
+    # qubit corresponds to the *last* axis in the tensor etc.)
48 
+    qubit_axes = tuple(n_state_qubits - 1 - np.asarray(qubits))
49 
+
50 
+    # Applying the gate to the state vector is then the tensor product over the appropriate axes
51 
+    axes = (np.arange(n_gate_qubits, 2 * n_gate_qubits), qubit_axes)
52 
+    new_state = np.tensordot(gate, state, axes=axes)
53 
+
54 
+    # tensordot effectively re-orders the qubits such that the qubits we operated
55 
+    # on are in the most-significant positions (i.e. their axes come first). We
56 
+    # thus need to transpose the axes to place them back into their original positions.
57 
+    untouched_axes = tuple(
58 
+        idx for idx in range(n_state_qubits) if idx not in qubit_axes
59 
+    )
60 
+    inverse_permutation = np.argsort(qubit_axes + untouched_axes)
61 
+    return np.transpose(new_state, inverse_permutation).reshape(-1)
62 
+
63 
+
31 64 
 def _check_valid_gate(gate):
32 65 
     if not (
33 66 
         # is an array
Browse code

Compute number of qubits by using bit length rather than logarithms

This is more idiomatic.

Joseph Weston authored on 15/11/2019 17:32:29
Showing 1 changed files
qsim/gate.py
History View file @ d0b4a81
... ... 
@@ -38,7 +38,7 @@ def _check_valid_gate(gate):
38 38 
         and gate.shape[0] == gate.shape[1]
39 39 
         # has size 2**n, n > 1
40 40 
         and np.log2(gate.shape[0]).is_integer()
41 
-        and np.log2(gate.shape[0]) > 0
41 
+        and gate.shape[0].bit_length() > 1
42 42 
         # is unitary
43 43 
         and np.allclose(gate @ gate.conjugate().transpose(), np.identity(gate.shape[0]))
44 44 
     ):
... ... 
@@ -52,9 +52,7 @@ def n_qubits(gate):
52 52 
     an integer power of 2.
53 53 
     """
54 54 
     _check_valid_gate(gate)
55 
-    n = np.log2(gate.shape[0])
56 
-    assert n.is_integer()
57 
-    return int(n)
55 
+    return gate.shape[0].bit_length() - 1
58 56
59 57
60 58 
 def controlled(gate):
Browse code

Add basic quantum gates

Joseph Weston authored on 10/11/2019 16:33:08
Showing 1 changed files
qsim/gate.py
History View file @ 0a4b3d0
... ... 
@@ -1,3 +1,128 @@
1 
-"""Quantum gate operations"""
1 
+"""Quantum gate operations
2 2
3 
-__all__ = []  # type: ignore
3 
+A quantum gate acting on :math:`n` qubits is a :math:`2^n×2^n` unitary
4 
+matrix written in the computational basis.
5 
+"""
6 
+
7 
+import numpy as np
8 
+
9 
+__all__ = [
10 
+    "n_qubits",
11 
+    "controlled",
12 
+    # -- Single qubit gates --
13 
+    "id",
14 
+    "x",
15 
+    "y",
16 
+    "z",
17 
+    "not_",
18 
+    "sqrt_not",
19 
+    "phase_shift",
20 
+    # -- 2 qubit gates --
21 
+    "cnot",
22 
+    "swap",
23 
+    # -- 3 qubit gates --
24 
+    "toffoli",
25 
+    "cswap",
26 
+    "fredkin",
27 
+    "deutsch",
28 
+]  # type: ignore
29 
+
30 
+
31 
+def _check_valid_gate(gate):
32 
+    if not (
33 
+        # is an array
34 
+        isinstance(gate, np.ndarray)
35 
+        # is complex
36 
+        and np.issubdtype(gate.dtype, np.complex128)
37 
+        # is square
38 
+        and gate.shape[0] == gate.shape[1]
39 
+        # has size 2**n, n > 1
40 
+        and np.log2(gate.shape[0]).is_integer()
41 
+        and np.log2(gate.shape[0]) > 0
42 
+        # is unitary
43 
+        and np.allclose(gate @ gate.conjugate().transpose(), np.identity(gate.shape[0]))
44 
+    ):
45 
+        raise ValueError("Gate is not valid")
46 
+
47 
+
48 
+def n_qubits(gate):
49 
+    """Return the number of qubits that a gate acts on.
50 
+
51 
+    Raises ValueError if 'gate' does not have a shape that is
52 
+    an integer power of 2.
53 
+    """
54 
+    _check_valid_gate(gate)
55 
+    n = np.log2(gate.shape[0])
56 
+    assert n.is_integer()
57 
+    return int(n)
58 
+
59 
+
60 
+def controlled(gate):
61 
+    """Return a controlled quantum gate, given a quantum gate.
62 
+
63 
+    If 'gate' operates on :math:`n` qubits, then the controlled gate operates
64 
+    on :math:`n+1` qubits, where the most-significant qubit is the control.
65 
+
66 
+    Parameters
67 
+    ----------
68 
+    gate : np.ndarray[complex]
69 
+        A quantum gate acting on :math:`n` qubits;
70 
+        a :math:`2^n×2^n` unitary matrix in the computational basis.
71 
+
72 
+    Returns
73 
+    -------
74 
+    controlled_gate : np.ndarray[(2**(n+1), 2**(n+1)), complex]
75 
+    """
76 
+    _check_valid_gate(gate)
77 
+    n = gate.shape[0]
78 
+    zeros = np.zeros((n, n))
79 
+    return np.block([[np.identity(n), zeros], [zeros, gate]])
80 
+
81 
+
82 
+# -- Single qubit gates --
83 
+
84 
+#: The identity gate on 1 qubit
85 
+id = np.identity(2, complex)
86 
+#: Pauli X gate
87 
+x = np.array([[0, 1], [1, 0]], complex)
88 
+#: NOT gate
89 
+not_ = x
90 
+#: Pauli Y gate
91 
+y = np.array([[0, -1j], [1j, 0]], complex)
92 
+#: Pauli Z gate
93 
+z = np.array([[1, 0], [0, -1]], complex)
94 
+#: SQRT(NOT) gate
95 
+sqrt_not = 0.5 * (1 + 1j * id - 1j * x)
96 
+#: Hadamard gate
97 
+hadamard = np.sqrt(0.5) * (x + z)
98 
+
99 
+
100 
+def phase_shift(phi):
101 
+    "Return a gate that shifts the phase of :math:`|1⟩` by :math:`φ`."
102 
+    return np.array([[1, 0], [0, np.exp(1j * phi)]])
103 
+
104 
+
105 
+# -- Two qubit gates --
106 
+
107 
+#: Controlled NOT gate
108 
+cnot = controlled(x)
109 
+#: SWAP gate
110 
+swap = np.identity(4, complex)[:, (0, 2, 1, 3)]
111 
+
112 
+# -- Three qubit gates --
113 
+
114 
+#: Toffoli (CCNOT) gate
115 
+toffoli = controlled(cnot)
116 
+#: Controlled SWAP gate
117 
+cswap = controlled(swap)
118 
+#: Fredkin gate
119 
+fredkin = cswap
120 
+
121 
+
122 
+def deutsch(phi):
123 
+    "Return a Deutsch gate for angle :math:`φ`."
124 
+    gate = np.identity(8, complex)
125 
+    gate[-2:, -2:] = np.array(
126 
+        [[1j * np.cos(phi), np.sin(phi)], [np.sin(phi), 1j * np.cos(phi)]]
127 
+    )
128 
+    return gate
Browse code

Add mypy configuration

Joseph Weston authored on 09/11/2019 16:36:39
Showing 1 changed files
qsim/gate.py
History View file @ 5453af1
... ... 
@@ -1,3 +1,3 @@
1 1 
 """Quantum gate operations"""
2 2
3 
-__all__ = []
3 
+__all__ = []  # type: ignore
Browse code

Add bare package and pyproject.toml

Joseph Weston authored on 09/11/2019 00:46:10
Showing 1 changed files
qsim/gate.py
History View file @ 346cf14
1 1 
new file mode 100644
... ... 
@@ -0,0 +1,3 @@
1 
+"""Quantum gate operations"""
2 
+
3 
+__all__ = []