"""Operators and states for 1D cartesian position and momentum.
TODO:
* Add 3D classes to mappings in operatorset.py
"""
from __future__ import print_function, division
from sympy import DiracDelta, exp, I, Interval, pi, S, sqrt
from sympy.core.compatibility import range
from sympy.physics.quantum.constants import hbar
from sympy.physics.quantum.hilbert import L2
from sympy.physics.quantum.operator import DifferentialOperator, HermitianOperator
from sympy.physics.quantum.state import Ket, Bra, State
__all__ = [
'XOp',
'YOp',
'ZOp',
'PxOp',
'X',
'Y',
'Z',
'Px',
'XKet',
'XBra',
'PxKet',
'PxBra',
'PositionState3D',
'PositionKet3D',
'PositionBra3D'
]
#-------------------------------------------------------------------------
# Position operators
#-------------------------------------------------------------------------
[docs]class XOp(HermitianOperator):
"""1D cartesian position operator."""
@classmethod
def default_args(self):
return ("X",)
@classmethod
def _eval_hilbert_space(self, args):
return L2(Interval(S.NegativeInfinity, S.Infinity))
def _eval_commutator_PxOp(self, other):
return I*hbar
def _apply_operator_XKet(self, ket):
return ket.position*ket
def _apply_operator_PositionKet3D(self, ket):
return ket.position_x*ket
def _represent_PxKet(self, basis, **options):
index = options.pop("index", 1)
states = basis._enumerate_state(2, start_index=index)
coord1 = states[0].momentum
coord2 = states[1].momentum
d = DifferentialOperator(coord1)
delta = DiracDelta(coord1 - coord2)
return I*hbar*(d*delta)
[docs]class YOp(HermitianOperator):
""" Y cartesian coordinate operator (for 2D or 3D systems) """
@classmethod
def default_args(self):
return ("Y",)
@classmethod
def _eval_hilbert_space(self, args):
return L2(Interval(S.NegativeInfinity, S.Infinity))
def _apply_operator_PositionKet3D(self, ket):
return ket.position_y*ket
[docs]class ZOp(HermitianOperator):
""" Z cartesian coordinate operator (for 3D systems) """
@classmethod
def default_args(self):
return ("Z",)
@classmethod
def _eval_hilbert_space(self, args):
return L2(Interval(S.NegativeInfinity, S.Infinity))
def _apply_operator_PositionKet3D(self, ket):
return ket.position_z*ket
#-------------------------------------------------------------------------
# Momentum operators
#-------------------------------------------------------------------------
[docs]class PxOp(HermitianOperator):
"""1D cartesian momentum operator."""
@classmethod
def default_args(self):
return ("Px",)
@classmethod
def _eval_hilbert_space(self, args):
return L2(Interval(S.NegativeInfinity, S.Infinity))
def _apply_operator_PxKet(self, ket):
return ket.momentum*ket
def _represent_XKet(self, basis, **options):
index = options.pop("index", 1)
states = basis._enumerate_state(2, start_index=index)
coord1 = states[0].position
coord2 = states[1].position
d = DifferentialOperator(coord1)
delta = DiracDelta(coord1 - coord2)
return -I*hbar*(d*delta)
X = XOp('X')
Y = YOp('Y')
Z = ZOp('Z')
Px = PxOp('Px')
#-------------------------------------------------------------------------
# Position eigenstates
#-------------------------------------------------------------------------
[docs]class XKet(Ket):
"""1D cartesian position eigenket."""
@classmethod
def _operators_to_state(self, op, **options):
return self.__new__(self, *_lowercase_labels(op), **options)
def _state_to_operators(self, op_class, **options):
return op_class.__new__(op_class,
*_uppercase_labels(self), **options)
@classmethod
def default_args(self):
return ("x",)
@classmethod
def dual_class(self):
return XBra
@property
def position(self):
"""The position of the state."""
return self.label[0]
def _enumerate_state(self, num_states, **options):
return _enumerate_continuous_1D(self, num_states, **options)
def _eval_innerproduct_XBra(self, bra, **hints):
return DiracDelta(self.position - bra.position)
def _eval_innerproduct_PxBra(self, bra, **hints):
return exp(-I*self.position*bra.momentum/hbar)/sqrt(2*pi*hbar)
[docs]class XBra(Bra):
"""1D cartesian position eigenbra."""
@classmethod
def default_args(self):
return ("x",)
@classmethod
def dual_class(self):
return XKet
@property
def position(self):
"""The position of the state."""
return self.label[0]
[docs]class PositionState3D(State):
""" Base class for 3D cartesian position eigenstates """
@classmethod
def _operators_to_state(self, op, **options):
return self.__new__(self, *_lowercase_labels(op), **options)
def _state_to_operators(self, op_class, **options):
return op_class.__new__(op_class,
*_uppercase_labels(self), **options)
@classmethod
def default_args(self):
return ("x", "y", "z")
@property
def position_x(self):
""" The x coordinate of the state """
return self.label[0]
@property
def position_y(self):
""" The y coordinate of the state """
return self.label[1]
@property
def position_z(self):
""" The z coordinate of the state """
return self.label[2]
[docs]class PositionKet3D(Ket, PositionState3D):
""" 3D cartesian position eigenket """
def _eval_innerproduct_PositionBra3D(self, bra, **options):
x_diff = self.position_x - bra.position_x
y_diff = self.position_y - bra.position_y
z_diff = self.position_z - bra.position_z
return DiracDelta(x_diff)*DiracDelta(y_diff)*DiracDelta(z_diff)
@classmethod
def dual_class(self):
return PositionBra3D
[docs]class PositionBra3D(Bra, PositionState3D):
""" 3D cartesian position eigenbra """
@classmethod
def dual_class(self):
return PositionKet3D
#-------------------------------------------------------------------------
# Momentum eigenstates
#-------------------------------------------------------------------------
[docs]class PxKet(Ket):
"""1D cartesian momentum eigenket."""
@classmethod
def _operators_to_state(self, op, **options):
return self.__new__(self, *_lowercase_labels(op), **options)
def _state_to_operators(self, op_class, **options):
return op_class.__new__(op_class,
*_uppercase_labels(self), **options)
@classmethod
def default_args(self):
return ("px",)
@classmethod
def dual_class(self):
return PxBra
@property
def momentum(self):
"""The momentum of the state."""
return self.label[0]
def _enumerate_state(self, *args, **options):
return _enumerate_continuous_1D(self, *args, **options)
def _eval_innerproduct_XBra(self, bra, **hints):
return exp(I*self.momentum*bra.position/hbar)/sqrt(2*pi*hbar)
def _eval_innerproduct_PxBra(self, bra, **hints):
return DiracDelta(self.momentum - bra.momentum)
[docs]class PxBra(Bra):
"""1D cartesian momentum eigenbra."""
@classmethod
def default_args(self):
return ("px",)
@classmethod
def dual_class(self):
return PxKet
@property
def momentum(self):
"""The momentum of the state."""
return self.label[0]
#-------------------------------------------------------------------------
# Global helper functions
#-------------------------------------------------------------------------
def _enumerate_continuous_1D(*args, **options):
state = args[0]
num_states = args[1]
state_class = state.__class__
index_list = options.pop('index_list', [])
if len(index_list) == 0:
start_index = options.pop('start_index', 1)
index_list = list(range(start_index, start_index + num_states))
enum_states = [0 for i in range(len(index_list))]
for i, ind in enumerate(index_list):
label = state.args[0]
enum_states[i] = state_class(str(label) + "_" + str(ind), **options)
return enum_states
def _lowercase_labels(ops):
if not isinstance(ops, set):
ops = [ops]
return [str(arg.label[0]).lower() for arg in ops]
def _uppercase_labels(ops):
if not isinstance(ops, set):
ops = [ops]
new_args = [str(arg.label[0])[0].upper() +
str(arg.label[0])[1:] for arg in ops]
return new_args
