Source code for sympy.physics.quantum.operatorset

""" A module for mapping operators to their corresponding eigenstates
and vice versa

It contains a global dictionary with eigenstate-operator pairings.
If a new state-operator pair is created, this dictionary should be
updated as well.

It also contains functions operators_to_state and state_to_operators
for mapping between the two. These can handle both classes and
instances of operators and states. See the individual function
descriptions for details.

TODO List:
- Update the dictionary with a complete list of state-operator pairs

from sympy.physics.quantum.cartesian import (XOp, YOp, ZOp, XKet, PxOp, PxKet,
from sympy.physics.quantum.operator import Operator
from sympy.physics.quantum.state import StateBase, BraBase, Ket
from sympy.physics.quantum.spin import (JxOp, JyOp, JzOp, J2Op, JxKet, JyKet,

__all__ = [

#state_mapping stores the mappings between states and their associated
#operators or tuples of operators. This should be updated when new
#classes are written! Entries are of the form PxKet : PxOp or
#something like 3DKet : (ROp, ThetaOp, PhiOp)

#frozenset is used so that the reverse mapping can be made
#(regular sets are not hashable because they are mutable
state_mapping = { JxKet : frozenset((J2Op, JxOp)),
                  JyKet : frozenset((J2Op, JyOp)),
                  JzKet : frozenset((J2Op, JzOp)),
                  Ket : Operator,
                  PositionKet3D : frozenset((XOp, YOp, ZOp)),
                  PxKet : PxOp,
                  XKet : XOp }

op_mapping = dict((v,k) for k,v in state_mapping.iteritems())

[docs]def operators_to_state(operators, **options): """ Returns the eigenstate of the given operator or set of operators A global function for mapping operator classes to their associated states. It takes either an Operator or a set of operators and returns the state associated with these. This function can handle both instances of a given operator or just the class itself (i.e. both XOp() and XOp) There are multiple use cases to consider: 1) A class or set of classes is passed: First, we try to instantiate default instances for these operators. If this fails, then the class is simply returned. If we succeed in instantiating default instances, then we try to call state._operators_to_state on the operator instances. If this fails, the class is returned. Otherwise, the instance returned by _operators_to_state is returned. 2) An instance or set of instances is passed: In this case, state._operators_to_state is called on the instances passed. If this fails, a state class is returned. If the method returns an instance, that instance is returned. In both cases, if the operator class or set does not exist in the state_mapping dictionary, None is returned. Parameters ========== arg: Operator or set The class or instance of the operator or set of operators to be mapped to a state Examples ======== >>> from sympy.physics.quantum.cartesian import XOp, PxOp >>> from sympy.physics.quantum.operatorset import operators_to_state >>> from sympy.physics.quantum.operator import Operator >>> operators_to_state(XOp) |x> >>> operators_to_state(XOp()) |x> >>> operators_to_state(PxOp) |px> >>> operators_to_state(PxOp()) |px> >>> operators_to_state(Operator) |psi> >>> operators_to_state(Operator()) |psi> """ if not (isinstance(operators, Operator) \ or isinstance(operators, set) or issubclass(operators, Operator)): raise NotImplementedError("Argument is not an Operator or a set!") if isinstance(operators, set): for s in operators: if not (isinstance(s, Operator) \ or issubclass(s, Operator)): raise NotImplementedError("Set is not all Operators!") #ops = tuple(operators) ops = frozenset(operators) if ops in op_mapping: #ops is a list of classes in this case #Try to get an object from default instances of the #operators...if this fails, return the class try: op_instances = [op() for op in ops] ret = _get_state(op_mapping[ops], set(op_instances), **options) except NotImplementedError: ret = op_mapping[ops] return ret else: tmp = [type(o) for o in ops] classes = frozenset(tmp) if classes in op_mapping: ret = _get_state(op_mapping[classes], ops, **options) else: ret = None return ret else: if operators in op_mapping: try: op_instance = operators() ret = _get_state(op_mapping[operators], op_instance, **options) except NotImplementedError: ret = op_mapping[operators] return ret elif type(operators) in op_mapping: return _get_state(op_mapping[type(operators)], operators, **options) else: return None
[docs]def state_to_operators(state, **options): """ Returns the operator or set of operators corresponding to the given eigenstate A global function for mapping state classes to their associated operators or sets of operators. It takes either a state class or instance. This function can handle both instances of a given state or just the class itself (i.e. both XKet() and XKet) There are multiple use cases to consider: 1) A state class is passed: In this case, we first try instantiating a default instance of the class. If this succeeds, then we try to call state._state_to_operators on that instance. If the creation of the default instance or if the calling of _state_to_operators fails, then either an operator class or set of operator classes is returned. Otherwise, the appropriate operator instances are returned. 2) A state instance is returned: Here, state._state_to_operators is called for the instance. If this fails, then a class or set of operator classes is returned. Otherwise, the instances are returned. In either case, if the state's class does not exist in state_mapping, None is returned. Parameters ========== arg: StateBase class or instance (or subclasses) The class or instance of the state to be mapped to an operator or set of operators Examples ======== >>> from sympy.physics.quantum.cartesian import XKet, PxKet, XBra, PxBra >>> from sympy.physics.quantum.operatorset import state_to_operators >>> from sympy.physics.quantum.state import Ket, Bra >>> state_to_operators(XKet) X >>> state_to_operators(XKet()) X >>> state_to_operators(PxKet) Px >>> state_to_operators(PxKet()) Px >>> state_to_operators(PxBra) Px >>> state_to_operators(XBra) X >>> state_to_operators(Ket) O >>> state_to_operators(Bra) O """ if not (isinstance(state, StateBase) or issubclass(state, StateBase)): raise NotImplementedError("Argument is not a state!") if state in state_mapping: #state is a class state_inst = _make_default(state) try: ret = _get_ops(state_inst, \ _make_set(state_mapping[state]), **options) except (NotImplementedError, TypeError): ret = state_mapping[state] elif type(state) in state_mapping: ret = _get_ops(state, \ _make_set(state_mapping[type(state)]), **options) elif isinstance(state, BraBase) and state.dual_class() in state_mapping: ret = _get_ops(state, \ _make_set(state_mapping[state.dual_class()])) elif issubclass(state, BraBase) and state.dual_class() in state_mapping: state_inst = _make_default(state) try: ret = _get_ops(state_inst, \ _make_set(state_mapping[state.dual_class()])) except (NotImplementedError, TypeError): ret = state_mapping[state.dual_class()] else: ret = None return _make_set(ret)
def _make_default(expr): try: ret = expr() except Exception: ret = expr return ret def _get_state(state_class, ops, **options): # Try to get a state instance from the operator INSTANCES. # If this fails, get the class try: ret = state_class._operators_to_state(ops, **options) except NotImplementedError: ret = _make_default(state_class) return ret def _get_ops(state_inst, op_classes, **options): # Try to get operator instances from the state INSTANCE. # If this fails, just return the classes try: ret = state_inst._state_to_operators(op_classes, **options) except NotImplementedError: if isinstance(op_classes, (set, tuple, frozenset)): ret = tuple(map(lambda x: _make_default(x), op_classes)) else: ret = _make_default(op_classes) if isinstance(ret, set) and len(ret) == 1: return ret[0] return ret def _make_set(ops): if isinstance(ops, (tuple, list, frozenset)): return set(ops) else: return ops