Add extract_expression_from_wavefunction to sympy.physics.quantum.state.Wavefunction

.mailmap

@@ -1644,6 +1644,7 @@ znxftw <vishnu2101@gmail.com>
 zsc347 <zsc347@gmail.com>
 zzc <1378113190@qq.com> zzc <58017008+zzc0430@users.noreply.github.com>
 zzj <29055749+zjzh@users.noreply.github.com>
+Ícaro <icarosadero@gmail.com>
 Óscar Nájera <najera.oscar@gmail.com>
 Øyvind Jensen <jensen.oyvind@gmail.com>
 Łukasz Pankowski <lukpank@o2.pl>

AUTHORS

@@ -1266,4 +1266,4 @@ Augusto Borges <borges.augustoar@gmail.com>
 Han Wei Ang <ang.h.w@u.nus.edu>
 Pablo <48098178+PabloRuizCuevas@users.noreply.github.com>
 Congxu Yang <u7189828@anu.edu.au>
-Saicharan <62512681+saicharan2804@users.noreply.github.com>
+Saicharan <62512681+saicharan2804@users.noreply.github.com>

sympy/physics/quantum/state.py

@@ -1,5 +1,6 @@
 """Dirac notation for states."""
 
+from sympy import KroneckerDelta
 from sympy.core.cache import cacheit
 from sympy.core.containers import Tuple
 from sympy.core.expr import Expr
@@ -643,7 +644,7 @@ class OrthogonalKet(OrthogonalState, KetBase):
         >>> (OrthogonalBra(n)*OrthogonalKet(n+1)).doit()
         0
         >>> (OrthogonalBra(n)*OrthogonalKet(m)).doit()
-        <n|m>
+        KroneckerDelta(m, n)
     """
 
     @classmethod
@@ -665,7 +666,7 @@ def _eval_innerproduct(self, bra, **hints):
                 return S.Zero # i.e. Integer(0)
 
             if is_zero is None:
-                return None
+                return KroneckerDelta(arg, bra_arg)
 
         return S.One # i.e. Integer(1)
 
@@ -909,6 +910,50 @@ def expr(self):
         """
         return self._args[0]
 
+    @staticmethod
+    def extract_expression_from_wavefunction(input_expression):
+        """
+        This function recursively traverses the given expression, replacing any instances of Wavefunction with their
+        internal expressions.
+
+        Parameters
+        ==========
+
+        input_expression : sympy.Expr
+            The expression that needs to be simplified.
+
+        Example
+        =======
+
+        import sympy as sp
+        from sympy.physics.quantum.state import Wavefunction
+
+        R = sp.Function('R')
+        Z = sp.Function('Z')
+        x,y = sp.symbols('x y', real=True)
+
+        ϕ = Wavefunction(R(x)*Z(y), x, y)
+
+        extract_expression_from_wavefunction(ϕ + ϕ)
+
+        Returns
+        =======
+
+        sympy.Expr
+            The simplified expression with Wavefunction instances replaced by their internal expressions.
+        """
+        def replace_wavefunctions(expression):
+            simplified_expression = expression
+            for argument in expression.args:
+                if argument.func == Wavefunction:
+                    simplified_expression = simplified_expression.subs(argument, argument.expr)
+                else:
+                    new_term = replace_wavefunctions(argument)
+                    simplified_expression = simplified_expression.subs(argument, new_term)
+            return simplified_expression
+
+        return replace_wavefunctions(input_expression)
+
     @property
     def is_normalized(self):
         """

sympy/physics/quantum/tests/test_state.py

@@ -1,3 +1,4 @@
+from sympy import KroneckerDelta
 from sympy.core.add import Add
 from sympy.core.function import diff
 from sympy.core.mul import Mul
@@ -245,4 +246,4 @@ def test_orthogonal_states():
     assert braket.doit() == 0
 
     braket = OrthogonalBra(x) * OrthogonalKet(y)
-    assert braket.doit() == braket
+    assert braket.doit() == KroneckerDelta(x, y)

sympy/testing/quality_unicode.py

@@ -52,6 +52,9 @@
 
     # Explanation of symbols uses greek letters
     r'*/sympy/core/symbol.py',
+
+    # Greek letter used as variable
+    r'*/sympy/physics/quantum/state.py',
 ]
 
 unicode_strict_whitelist = [