Cirq: creating a new device with custom coupling topology?

Question

Cirq has two in-built realizations of quantum hardware, which are realized as GridQubit() and LineQubit() classes (naming convention is slightly disturbing:).

GridQubit device mimics connectivity of Google's quantum chips (Bristlecone, Sycamore) and qubits are arranged in a 2D grid with nearest-neighbor couplings. https://github.com/quantumlib/Cirq/blob/master/cirq/devices/grid_qubit.py

LineQubit device represents chips with 1D geometry, where qubits are arranged in a line and again only nearest-neighbor qubits are coupled.

Is there any possibility to specify a custom hardware coupling map? E.g. to specify adjacency matrix of new connectivity graph?

It seems that a user has to create his/her own device class for such functionality.

Answer 1

Generally, yes, it is expected that you would define your own device and perhaps your own qubits in order to make custom topologies.

There is currently a graph device package in the "contrib" package, which allows you to specify the connectivity graph for a device. But as with anything in contrib it may be a bit clunky and could disappear/change from version to version.

import cirq.contrib.graph_device