Advanced Quantum Testbed (AQT)

Raveh Neeman

doi:10.5281/zenodo.22674814

Lawrence Berkeley National Laboratory · superconducting circuits · DEPLOYED (open testbed) (2018-2026) · 8 physical qubits · access: open user testbed (no cost for non-proprietary work that will be published; DOE ASCR); User Program being restructured, with no open call for user proposals on the usual annual cycle; collaborations by contact (aqt@lbl.gov)

architecture: Transmon lattice with tunable couplers · Open on the map

Register profile — the machine's variant of its architecture

qubit type: fixed-frequency transmon (5.2-5.8 GHz, ~250 MHz anharmonicity); qutrit operation

gate mechanism: cross-resonance between fixed-frequency qubits; all-microwave CZ; parametric fSim

connectivity: ring, nearest-neighbour

control: QubiC 2.0 (Xilinx ZCU216 RFSoC + custom analog front end); Zurich Instruments HDAWG/UHFQA/PQSC

control placement: room-temp

readout: multiplexed dispersive readout with TWPA; three-state readout fidelity >95%

gate evidence: no published figure

Technologies by layer — the machine's cell per layer

1 Qubit carrier	Transmon · primary ▦ ✅ eight fixed-frequency transmons in a ring (primary QPU); 9-qubit flux-tunable MIT-LL chip also offered
2 Encoding	Bare physical qubit (no encoding) · primary ◌ 🔎 bare transmon levels; three-state (qutrit) operation also offered
3 Gate mechanism	Cross-resonance (fixed-frequency, all-microwave) · primary ▦ ✅ cross-resonance CNOT between fixed-frequency nearest neighbours, error 1-4%; all-microwave CZ 0.5-1%
4 Connectivity / transport	Static nearest-neighbour lattice · primary ▦ ✅ ring with nearest-neighbour connectivity
5 Control	Room-temperature electronics + per-qubit coax/flex · primary ▦ ✅ room-temperature QubiC 2.0 RFSoC controller and Zurich Instruments electronics; mid-circuit measurement and fast feedback
6 Readout	Dispersive microwave readout (+TWPA, Purcell) · primary ▦ ✅ multiplexed dispersive readout with TWPA; three-state readout fidelity >95%
7 Code	— none — nothing in this layer ◌ 🔎 no QEC code as a machine feature; open testbed for control and QCVV methods
8 Decoder	— none — nothing in this layer ◌ 🔎 no decoder
9 Interconnect	— none — nothing in this layer ◌ 🔎 single-chip QPU; no interconnect
10 Manufacturing	Superconducting-qubit lithography (Al/AlOx/Al junctions, Nb wiring, 300 mm) · primary ◌ 🔎 superconducting-qubit lithography; primary chip fab site not stated (9-qubit chip from MIT-LL)

evidence: ✅ 5 / 10