  We report high qubit coherence as well as low crosstalk and single-qubit gate
errors in a superconducting circuit architecture that promises to be tileable
to 2D lattices of qubits. The architecture integrates an inductively shunted
cavity enclosure into a design featuring non-galvanic out-of-plane control
wiring and qubits and resonators fabricated on opposing sides of a substrate.
The proof-of-principle device features four uncoupled transmon qubits and
exhibits average energy relaxation times $T_1=149(38)~\mu$s, pure echoed
dephasing times $T_{\phi,e}=189(34)~\mu$s, and single-qubit gate fidelities
$F=99.982(4)\%$ as measured by simultaneous randomized benchmarking. The 3D
integrated nature of the control wiring means that qubits will remain
addressable as the architecture is tiled to form larger qubit lattices. Band
structure simulations are used to predict that the tiled enclosure will still
provide a clean electromagnetic environment to enclosed qubits at arbitrary
scale.
