A superinductor in a deep sub-micron integrated circuit
A superinductor in a deep sub-micron integrated circuit
Superinductors are circuit elements characterised by an intrinsic impedance in excess of the superconducting resistance quantum ($R_\text{Q}\approx6.45~$k$Ω$), with applications from metrology and sensing to quantum computing. However, they are typically obtained using exotic materials with high density inductance such as Josephson junctions, superconducting nanowires or twisted two-dimensional materials. Here, we present a superinductor realised within a silicon integrated circuit (IC), exploiting the high kinetic inductance ($\sim 1$~nH/$\square$) of TiN thin films native to the manufacturing process (22-nm FDSOI). By interfacing the superinductor to a silicon quantum dot formed within the same IC, we demonstrate a radio-frequency single-electron transistor (rfSET), the most widely used sensor in semiconductor-based quantum computers. The integrated nature of the rfSET reduces its parasitics which, together with the high impedance, yields a sensitivity improvement of more than two orders of magnitude over the state-of-the-art, combined with a 10,000-fold area reduction. Beyond providing the basis for dense arrays of integrated and high-performance qubit sensors, the realization of high-kinetic-inductance superconducting devices integrated within modern silicon ICs opens many opportunities, including kinetic-inductance detector arrays for astronomy and the study of metamaterials and quantum simulators based on 1D and 2D resonator arrays.
Community Review
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This is a high-quality experimental paper demonstrating the integration of superconducting TiN thin films within a 22-nm CMOS process to create compact superinductors. The work is methodologically sound, presenting clear experimental data on the characterization of kinetic inductance in TiN films and their application in radio-frequency single-electron transistors (rfSETs). The mathematical framework is appropriate for the experimental context, using established superconductivity theory (Ginzburg-Landau) and circuit analysis. The experimental design is well-conceived, with proper controls and systematic parametric studies of temperature, magnetic field, and current dependencies. The demonstration of >100x sensitivity improvement and 10,000x area reduction compared to state-of-the-art represents significant practical advancement. The paper is exceptionally well-written with clear explanations of both the physics and the technological implications. While the core physics relies on established superconductivity principles, the engineering achievement of integrating these capabilities within standard CMOS processes is genuinely novel and practically important for quantum computing applications.
This review was generated by AI for research and educational purposes. It is not a substitute for formal peer review. All analyses are advisory; publication decisions are based on numerical score thresholds.
Key Equations (3)
Estimate of the characteristic impedance of the inductor-resonator formed by L_K and the inductor parasitic capacitance C_{L,par}. Used to evaluate whether impedance exceeds the superconducting resistance quantum.
Current-dependent nonlinearity of the kinetic inductance as a function of DC and RF currents, indicating Kerr-like behaviour and enabling three- and four-wave mixing.
Resonance-based extraction of the kinetic inductance L_K from measured resonant frequency f and total capacitance C_tot (C_tot = C_c + C + C_p).
Other Equations (4)
Relation between equivalent noise bandwidth (ENBW), low-pass filter cutoff f_LP and number of averages N_avg; and the conversion to integration time t_int.
Definition of signal-to-noise ratio used for rf readout, computed from I/Q centroids and variances of signal and background measurements.
Phenomenological temperature dependence of the kinetic inductance using Ginzburg–Landau Cooper-pair density approximation, showing divergence as T -> T_C.
2D Gaussian model used to fit the measured I-Q histograms and extract centroids and variances for SNR calculations.
Testable Predictions (4)
TiN thin films native to the 22-nm FDSOI process can produce kinetic inductance densities ≈1 nH/□ and integrated inductances up to ≈807 nH, yielding circuit impedances Z_L ≈11.5 kΩ that exceed the superconducting resistance quantum R_Q.
Falsifiable if: Independent four-point and RF-resonator measurements on equivalent 22-nm FDSOI TiN structures fail to reproduce L_K per square ≈1 nH/□, total L_K ≈800 nH, or measured Z_L that exceeds R_Q under similar temperature and geometry.
An rfSET formed in the same CMOS die and impedance-matched with the TiN superinductor attains a minimum integration time t_min as low as ≈1 ps and a >100× improvement in sensitivity compared to prior state-of-the-art rfSETs (reference t_min ≈625 ps).
Falsifiable if: Reproduction of the integrated rfSET under comparable cryogenic and measurement-chain conditions yields t_min >> 1 ps (e.g., comparable to or worse than 625 ps) and no >100× sensitivity improvement.
The TiN kinetic inductors exhibit resilience to in-plane magnetic fields up to ≈2 T, maintaining superconducting inductive behavior compatible with spin-qubit operation.
Falsifiable if: Applying in-plane magnetic fields near 2 T to equivalent TiN structures causes loss of superconductivity or collapse of inductive resonance at significantly lower fields (e.g., <1 T).
The nonlinear dependence of L_K on dc and rf currents enables operation in a parametric regime (three-/four-wave mixing) useful for enhanced readout sensitivity and parametric amplification.
Falsifiable if: Characterization of L_K vs drive current shows only linear behaviour up to the measured operating powers, with no evidence of parametric gain or sensitivity enhancement attributable to inductive nonlinearity.
Tags & Keywords
Keywords: superinductor, kinetic inductance, titanium nitride (TiN), 22-nm FDSOI CMOS, radio-frequency single-electron transistor (rfSET), quantum dot, high-impedance circuits, parametric amplification, cryogenic CMOS, single-spin readout
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arxiv.org/abs/2507.13202You Might Also Find Interesting
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