Mapping

In the quantum circuit model of computation, circuits manipulate qubits. These qubits exist as abstractions within a circuit and shall be called virtual (or logical). Mapping is the task of finding a one-to-one relation between virtual qubits and physical qubits, which denote the actual hardware units that store quantum bits, such that allow the execution of all gates.

In the circuit model, any pair of virtual qubits can interact, i.e., we can perform a two-qubit operation between any pair. The physical qubits in most quantum hardware, however, are not fully connected, meaning that not every pair of physical qubits can participate in the same quantum operation. These physical connectivity restrictions are known as coupling constraints.

The library divides mapping into two subtasks: placement and routing.

Placement

Placement tries to find a bijection between the set of virtual qubits and the set of physical qubits, such that the quantum device can execute all gates. Such perfect placement, however, might not exist. In this case, a placement algorithm might return an initial placement. When the placement is not enough, it is necessary to transform the circuit.

Function	Description
Heuristic SAT placement	Yet to be written.
Line placement	Yet to be written.
Random placement	yet to be written.
SAT placement	yet to be written.

Routing

Given an initial placement, a router uses SWAP operations to move the virtual qubits around the device topology whenever it finds an operation that acts on qubits that are physically separated. It routes the involved virtual qubits to adjacent physical qubits.

Function	Description
A* rotuer	Yet to be written.
JIT rotuer	yet to be written.
SABRE rotuer	yet to be written.
SAT rotuer	yet to be written.