Cryogenic Strain Cell Delivers 215 Microstrain on 200 μm Silicon Dies with Dual-Chip Symmetry

The design replaces prior cells optimized for thin high-aspect-ratio crystals with a symmetric dual-chip mount that cancels flexural and shear modes. Finite-element analysis shows stiff actuators plus symmetric loading reduce strain variation below 5% across a 5 mm die, a direct response to the square-profile chips used in silicon and superconducting qubit foundries. Experimental validation used a 200 μm Si die instrumented with strain gauges, confirming the target value without measurable electrostatic crosstalk to the device layer.

Existing strain-tuning literature, including work on valley-orbit control in Si/SiGe dots and piezo-tuned transmons, relied on cells that could not accommodate standard wire-bonded qubit chips or high-density microwave lines. This apparatus closes that gap by adding an interposer and grounded enclosure, enabling in-situ strain sweeps during coherence measurements without additional filtering stages.

The principal remaining constraint is the absence of data on functional qubit devices under load. Replicating the cell in a dilution refrigerator with gate-defined quantum dots would test whether the reported homogeneity translates to stable valley splitting or reduced charge noise. Parallel efforts at NIST and TU Delft on integrated piezo actuators suggest a combined platform could appear within two years.