ISMAGS

ISMAGS#

class pennylane_calculquebec.processing.steps.placement.ISMAGS(machine_name: str, use_benchmark=True, q1_acceptance=0.5, q2_acceptance=0.5, excluded_qubits=[], excluded_couplers=[])#

Bases: Placement

finds a mapping between the circuit’s wires and the machine’s qubits using the ISMAGS subgraph isomorphism algorithm

ISMAGS is similar to VF2 except it also considers symmetries which can make it faster in some cases

Plus, the networkx implementation has capabilities for searching for largest common subgraphs

constructor for placement algorithms

Parameters:

  • use_benchmark (bool, optional) – should we use benchmarks during placement? Defaults to True.

  • q1_acceptance (float, optional) – what is the level of acceptance for state 1 readout? Defaults to 0.5.

  • q2_acceptance (float, optional) – what is the level of acceptance for cz fidelity? Defaults to 0.5.

  • excluded_qubits (list, optional) – what qubits should we exclude from the mapping? Defaults to [].

  • excluded_couplers (list, optional) – what couplers should we exclude from the mapping? Defaults to [].

execute(tape)

places the circuit on the machine's connectivity using ISMAGS subgraph isomorphism algorithm
execute(tape)#

places the circuit on the machine’s connectivity using ISMAGS subgraph isomorphism algorithm

If there is no perfect match, the missing nodes are mapped with qubits that minimize the subsequent routing path

  1. find largest common subgraph

  2. for each unmapped node

    1. find the best neighbour (using cost function)

    2. find machine node with shortest path from already mapped machine node

  1. map wires in all operations and measurements

Parameters:

tape (QuantumTape) – The tape to act on

Raises:

Exception – There should be enough space on the machine to run the circuit

Returns:

The transformed quantum tape

Return type:

QuantumTape