  The trapped-ion QCCD (quantum charge-coupled device) architecture proposal
lays out a blueprint for a universal quantum computer. The design begins with
electrodes patterned on a two-dimensional surface configured to trap multiple
arrays of ions (or ion crystals). Communication within the ion crystal network
allows for the machine to be scaled while keeping the number of ions in each
crystal to a small number, thereby preserving the low error rates demonstrated
in trapped-ion experiments. By proposing to communicate quantum information by
moving the ions through space to interact with other distant ions, the
architecture creates a quantum computer endowed with full-connectivity.
However, engineering this fully-connected computer introduces a host of
difficulties that have precluded the architecture from being fully realized in
the twenty years since its proposal. Using a Honeywell cryogenic surface trap,
we report on the integration of all necessary ingredients of the QCCD
architecture into a programmable trapped-ion quantum computer. Using four and
six qubit circuits, the system level performance of the processor is quantified
by the fidelity of a teleported CNOT gate utilizing mid-circuit measurement and
a quantum volume measurement of $2^6=64$. By demonstrating that the low error
rates achievable in small ion crystals can be successfully integrated with a
scalable trap design, parallel optical delivery, and fast ion transport, the
QCCD architecture is shown to be a viable path toward large quantum computers.
Atomic ions provide perfectly identical, high-fidelity qubits. Our work shows
that the QCCD architecture built around these qubits will provide high
performance quantum computers, likely enabling important near-term
demonstrations such as quantum error correction and quantum advantage.
