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"""Hermitian conjugation."""
from sympy.core import Expr, Mul
from sympy.functions.elementary.complexes import adjoint
__all__ = [
'Dagger'
]
class Dagger(adjoint):
"""General Hermitian conjugate operation.
Explanation
===========
Take the Hermetian conjugate of an argument [1]_. For matrices this
operation is equivalent to transpose and complex conjugate [2]_.
Parameters
==========
arg : Expr
The SymPy expression that we want to take the dagger of.
Examples
========
Daggering various quantum objects:
>>> from sympy.physics.quantum.dagger import Dagger
>>> from sympy.physics.quantum.state import Ket, Bra
>>> from sympy.physics.quantum.operator import Operator
>>> Dagger(Ket('psi'))
<psi|
>>> Dagger(Bra('phi'))
|phi>
>>> Dagger(Operator('A'))
Dagger(A)
Inner and outer products::
>>> from sympy.physics.quantum import InnerProduct, OuterProduct
>>> Dagger(InnerProduct(Bra('a'), Ket('b')))
<b|a>
>>> Dagger(OuterProduct(Ket('a'), Bra('b')))
|b><a|
Powers, sums and products::
>>> A = Operator('A')
>>> B = Operator('B')
>>> Dagger(A*B)
Dagger(B)*Dagger(A)
>>> Dagger(A+B)
Dagger(A) + Dagger(B)
>>> Dagger(A**2)
Dagger(A)**2
Dagger also seamlessly handles complex numbers and matrices::
>>> from sympy import Matrix, I
>>> m = Matrix([[1,I],[2,I]])
>>> m
Matrix([
[1, I],
[2, I]])
>>> Dagger(m)
Matrix([
[ 1, 2],
[-I, -I]])
References
==========
.. [1] https://en.wikipedia.org/wiki/Hermitian_adjoint
.. [2] https://en.wikipedia.org/wiki/Hermitian_transpose
"""
def __new__(cls, arg):
if hasattr(arg, 'adjoint'):
obj = arg.adjoint()
elif hasattr(arg, 'conjugate') and hasattr(arg, 'transpose'):
obj = arg.conjugate().transpose()
if obj is not None:
return obj
return Expr.__new__(cls, arg)
def __mul__(self, other):
from sympy.physics.quantum import IdentityOperator
if isinstance(other, IdentityOperator):
return self
return Mul(self, other)
adjoint.__name__ = "Dagger"
adjoint._sympyrepr = lambda a, b: "Dagger(%s)" % b._print(a.args[0])
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