Placement of quantum circuits

Question

I have a question concerning the placement of quantum circuits on Google devices. Consider the following code:

import cirq
q           = [cirq.LineQubit(x) for x in range(5)]
circuit     = cirq.Circuit(cirq.CNOT.on(q[0],q[3]), cirq.CNOT.on(q[1],q[4]))
line        = cirq.google.line_on_device(cirq.google.Bristlecone, length=5)
circuit_opt = cirq.google.optimized_for_xmon(circuit=circuit, new_device=cirq.google.Bristlecone, qubit_map=lambda i: line[i.x])
simulator   = cirq.Simulator()
result = simulator.run(circuit, repetitions=1024)

This ad comparable codes yields the error

ValueError: Non-local interaction: cirq.CZ.on(cirq.GridQubit(0, 5), cirq.GridQubit(1, 7)).

Does Cirq provide a mechanism to automatically place (and route) a generic algorithm in the qubits 0..5 onto a concrete lattice structure?

Thanks in advance, Matthias

Answer 1

There is currently no code in cirq that attempts to rewrite connectivity-violating operations into a series of connectivity-satisfying operations. The reasoning for not including this functionality is basically that it is expected that any such rewriting step will produce a circuit that is longer than any realistic noise budget.

There are tools that work with cirq that do what you want, such as pytket.