pytreenet.time_evolution.time_evo_util package

Submodules

pytreenet.time_evolution.time_evo_util.update_path module

Module to find the update path of a TDVP algorithm.

class pytreenet.time_evolution.time_evo_util.update_path.TDVPUpdatePathFinder(state: TreeStructure)

Bases: object

Constructs the update path of a TDVP algorithm.

The update path should minimise the number of orthogonalisations, i.e. QR-decompositions, during the time-evolution. To this end the start and end node are chosen to be the two leafs which are furthest away from each other.

state

The tree topology to find the update path on.

Type:

TreeStructure

start

The node to start the update path at.

Type:

GraphNode

main_path

The main path, i.e. the longest path in the tree along which to run. For an MPS this would be the only path.

Type:

List[str]

find_furthest_non_visited_leaf(path: List[str]) → str

Finds the leaf that is furthest from the origin once and was not yet visited.

Parameters:

path (List[sr]) – A list of all node_ids already visited.

Returns:

The identifier of the leaf which is furthest away from the

main path and has not been visited yet.

Return type:

str

find_main_path_down_from_root(path: List[str]) → List[str]

Finds the main path which to traverse from the root to the last leaf.

Parameters:

path (List[str]) – The path already traversed.

Returns:

Main path from the root to the last leaf.

[root, node, node, … , leaf]

Return type:

List[str]

find_path() → List[str]

Finds the complete update path for a TDVP along a main path.

All nodes in branches are added before the branch origin in the main path.

find_start_node_id() → str

Finds the node id at which to start the TDVP update.

This would be the initial orthogonalisation center of the state that is to be time-evolved. Currently, we assume this site is the leaf furthest away from the root. # TODO: Allow option to find the leaves furthest away from one another.

Returns:

The node_id at which to start the update.

Return type:

str

path_down_from_root(path: List[str]) → List[str]

Finds the complete path from the root to the last leaf.

Parameters:

path (List[str]) – The path that was already traversed.

Returns:

The complete path from the root to the last leaf.

[root, node, node, … , leaf]

Return type:

List[str]

path_for_branch(branch_origin: str) → List[str]

Finds the node_ids that need to be visited after the last main path node and before branch_origin.

Parameters:

branch_origin (str) – The identifier of the node in the main path which has the branch as a subtree.

Returns:

The desired path. The children appear before their

parent.

Return type:

List[str]