cirq.experiments.build_entangling_layers

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Builds a sequence of gates that entangle all pairs of qubits on a grid.

cirq.experiments.build_entangling_layers(
    qubits: Sequence[cirq.devices.GridQubit],
    two_qubit_gate: cirq.ops.Gate
) -> List[cirq.circuits.Moment]

The qubits are restricted to be physically on a square grid with distinct row and column indices (not every node of the grid needs to have a qubit). To entangle all pairs of qubits, a user-specified two-qubit gate is applied between each and every pair of qubit that are next to each other. In general, a total of four sets of parallel operations are needed to perform all possible two-qubit gates. We proceed as follows:

The first layer applies two-qubit gates to qubits (i, j) and (i, j + 1) where i is any integer and j is an even integer. The second layer applies two-qubit gates to qubits (i, j) and (i + 1, j) where i is an even integer and j is any integer. The third layer applies two-qubit gates to qubits (i, j) and (i, j + 1) where i is any integer and j is an odd integer. The fourth layer applies two-qubit gates to qubits (i, j) and (i + 1, j) where i is an odd integer and j is any integer.

After the layers are built as above, any empty layer is ejected.:

         Cycle 1:                            Cycle 2:
q00 ── q01    q02 ── q03            q00    q01    q02    q03
                                     |      |      |      |
q10 ── q11    q12 ── q13            q10    q11    q12    q13

q20 ── q21    q22 ── q23            q20    q21    q22    q23
                                     |      |      |      |
q30 ── q31    q32 ── q33            q30    q31    q32    q33

          Cycle 3:                           Cycle 4:
q00    q01 ── q02    q03            q00    q01    q02    q03

q10    q11 ── q12    q13            q10    q11    q12    q13
                                     |      |      |      |
q20    q21 ── q22    q23            q20    q21    q22    q23

q30    q31 ── q32    q33            q30    q31    q32    q33