Cryostat platform: ProteoxLX 530 mm Plate Family
A five-qubit transmon cryostat on the QD Proteox LX-530 platform with four RF signal chains per qubit (XY drive, readout-in, readout-out, flux bias) plus shared pump and DC auxiliary chains. With over 80 components and 130 cable routes packed into six temperature stages, this preset illustrates the real-world wiring density challenges that emerge when scaling beyond a handful of qubits.
A dilution refrigerator cools in discrete stages. Each plate intercepts heat from the cables above and adds attenuation or filtering so thermal noise decreases as you approach the qubit at ~15 mK.
Twenty qubit feedthrough panels (4 per qubit) plus pump, DC, and thermometry panels crowd the vacuum flange, demonstrating panel occupancy limits.
Ten XY and readout-in attenuators intercept room-temperature noise. Flux and readout-out chains pass through with thermal anchoring.
Five HEMT amplifiers (one per readout-out chain) plus drive attenuators and flux low-pass filters. Total heat dissipation approaches the 1.5 W cooling budget.
Continued per-qubit XY attenuation and flux filtering at ~800 mK. Passthrough anchors for readout-in and readout-out chains thermalize cables without active components.
Penultimate per-qubit attenuation and filtering at ~100 mK. Cable bundles are tightly packed, making routing clearance the primary constraint.
Five sample packages, ten circulators, five final attenuators, five readout-in attenuators, and five flux filters at ~15 mK. Every microwatt of dissipation matters.
Five parallel 4-8 GHz microwave drive chains, one per qubit, each attenuated at every stage to suppress thermal photons from reaching the qubit.
Five readout stimulus chains delivering weak probe tones to each qubit's readout resonator. Attenuation keeps photon number below one at the device.
Five readout return chains carrying qubit-state-dependent signals upward. Each chain has dual circulators at MXC for isolation and a dedicated HEMT at 4 K.
Five DC/low-frequency lines for qubit frequency tuning via SQUID loop flux. Heavily low-pass filtered at every cold stage to reject high-frequency noise coupling.
Shared parametric amplifier pump tone chain. Attenuated at 50 K and 4 K, then passed through to the MXC stage for Josephson parametric amplifier operation.
Auxiliary DC bias and thermometry lines routed through dedicated feedthrough panels in the inter-sector gaps. Used for heater control and temperature monitoring.
Wiring density scales roughly as 4N for N transmon qubits (XY + readout-in + readout-out + flux per qubit), making panel real estate and cable routing the first bottleneck in multi-qubit systems.
Five HEMT amplifiers at 4 K dissipate ~50 mW total, consuming a significant fraction of the ~1.5 W cooling power at that stage and setting a practical scaling ceiling.
Cable bundle congestion between stages forces careful angular sector planning: each qubit occupies a 72-degree wedge with only ~24 degrees of inter-sector clearance.
The cumulative thermal load from 130+ cable segments directly reduces base temperature margin, requiring stainless-steel and NbTi cable materials to limit conductive heat transfer.