trying to add inverse U

Author: refraction-ray

tensorcircuit/gates.py

@@ -5,14 +5,14 @@
 import sys
 from copy import deepcopy
 from functools import reduce, partial
-from typing import Any, Callable, Optional, Sequence, List, Union
+from typing import Any, Callable, Optional, Sequence, List, Union, Tuple
 from operator import mul
 
 import numpy as np
 import tensornetwork as tn
 from scipy.stats import unitary_group
 
-from .cons import backend, dtypestr, npdtype
+from .cons import backend, dtypestr, npdtype, rdtypestr
 from .backends import get_backend  # type: ignore
 from .utils import arg_alias
 
@@ -466,6 +466,27 @@ def phase_gate(theta: float = 0) -> Gate:
     return Gate(unitary)
 
 
+# TODO(@refraction-ray): not correct now, correct impl required
+def get_u_parameter(m: Tensor) -> Tuple[Tensor, Tensor, Tensor]:
+    """
+    From the single qubit unitary to infer three angles of IBMUgate
+
+    :param m: _description_
+    :type m: Tensor
+    :return: theta, phi, lbd
+    :rtype: Tuple[Tensor, Tensor, Tensor]
+    """
+    print("wrong impl, dont use!")
+    a, b, c = m[0, 0], m[0, 1], m[1, 0]
+    if a == 0:
+        theta = np.pi
+    else:
+        theta = 2 * backend.atan(backend.sqrt(1 - a**2) / a)
+    lbd = -1j * backend.log(b * backend.sqrt(1 - a**2) / (a**2 - 1))
+    phi = -1j * backend.log(c / backend.sqrt(1 - a**2))
+    return array_to_tensor(theta, phi, lbd, dtype=rdtypestr)  # type: ignore
+
+
 def u_gate(theta: float = 0, phi: float = 0, lbd: float = 0) -> Gate:
     r"""
     IBMQ U gate following the converntion of OpenQASM3.0.

tensorcircuit/translation.py

@@ -151,6 +151,7 @@ def qir2qiskit(qir: List[Dict[str, Any]], n: int) -> Any:
                 )
             )
             qiskit_circ.unitary(qop, index[::-1], label=qis_name)
+        # TODO(@refraction-ray): support for phase gate and U, cU gate for the circuit translation
         else:  # r cr any gate
             qop = qi.Operator(
                 np.reshape(

tests/test_gates.py

@@ -1,6 +1,8 @@
 import sys
 import os
 import numpy as np
+import pytest
+from pytest_lazyfixture import lazy_fixture as lf
 
 thisfile = os.path.abspath(__file__)
 modulepath = os.path.dirname(os.path.dirname(thisfile))
@@ -31,6 +33,18 @@ def test_cu_gate():
     np.testing.assert_allclose(m[:2, :2], np.eye(2), atol=1e-5)
 
 
+@pytest.mark.skip(reason="to be implemented")
+@pytest.mark.parametrize("backend", [lf("npb"), lf("tfb"), lf("jaxb")])
+def test_get_u_parameter(backend, highp):
+    for _ in range(6):
+        hermitian = np.random.uniform(size=[2, 2])
+        hermitian += np.conj(np.transpose(hermitian))
+        unitary = tc.backend.expm(hermitian * 1.0j)
+        params = tc.gates.get_u_parameter(unitary)
+        unitary2 = tc.gates.u_gate(theta=params[0], phi=params[1], lbd=params[2])
+        np.testing.assert_allclose(unitary, unitary2.tensor, atol=1e-3)
+
+
 def test_exp_gate():
     c = tc.Circuit(2)
     c.exp(