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Glossary

Quantum glossary

Coupling map

Also: connectivity, topology, heavy hex

The graph of which physical qubits on a device can interact directly with a two-qubit gate.

Most chips connect each qubit only to a few neighbours. A circuit that needs a gate between distant qubits must first move the states together with SWAPs, which a compiler inserts during routing — at a real cost in noise.

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Related terms

  • Transpilation — Rewriting a circuit into the native gates and connectivity of a specific device, while optimising it.
  • SWAP gate — A two-qubit gate that exchanges the states of two qubits; it costs three CNOTs.