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arxiv: 2605.15554 · v1 · pith:QP7V4NMWnew · submitted 2026-05-15 · 🪐 quant-ph · cond-mat.mes-hall

Interface Piezoelectric Loss in Superconducting Qubits

Haoxin Zhou , Kangdi Yu , Yashwanth Balaji , Sanjit Shirol , Leo Sementilli , Zi-Huai Zhang , Adam Schwartzberg , Alp Sipahigil This is my paper

Pith reviewed 2026-05-20 19:44 UTC · model grok-4.3

classification 🪐 quant-ph cond-mat.mes-hall
keywords superconducting qubitsinterface piezoelectricitysurface acoustic wavesqubit lifetimeloss mechanismstransmonsilicon substratedissipation
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The pith

Piezoelectric coupling at the aluminum-silicon interface dissipates energy from superconducting qubits when tuned to mechanical resonances.

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The paper shows that transmon qubits fabricated on high-resistivity silicon exhibit up to a factor-of-two shorter lifetime when their transition frequency is brought into resonance with discrete mechanical modes of an embedded surface acoustic wave resonator. The shunt capacitor is designed to double as an interdigital transducer, allowing the qubit to exchange energy with those modes through piezoelectric coupling at the aluminum-silicon boundary. This establishes interface piezoelectricity as a loss channel separate from two-level systems. Readers care because the mechanism is expected to grow stronger with frequency and could set a practical limit on coherence in future high-frequency devices.

Core claim

The authors observe a clear reduction in qubit lifetime, reaching a factor of two, precisely when the transmon frequency matches mechanical resonances. They attribute the effect to energy transfer mediated by piezoelectric coupling at the aluminum-silicon interface and support the interpretation with multiphysics simulations showing that this channel can exceed two-level-system loss at higher frequencies.

What carries the argument

Interface piezoelectric coupling at the aluminum-silicon boundary, which converts qubit electrical energy into mechanical vibrations within the surface acoustic wave resonator.

Load-bearing premise

The observed lifetime reduction is produced by piezoelectric energy exchange at the aluminum-silicon interface rather than by fabrication differences, other loss mechanisms, or measurement artifacts.

What would settle it

Measuring identical qubit lifetimes when the transition frequency is tuned both on and off resonance with the mechanical modes would falsify the claimed piezoelectric loss channel.

Figures

Figures reproduced from arXiv: 2605.15554 by Adam Schwartzberg, Alp Sipahigil, Haoxin Zhou, Kangdi Yu, Leo Sementilli, Sanjit Shirol, Yashwanth Balaji, Zi-Huai Zhang.

Figure 1
Figure 1. Figure 1: FIG. 1 [PITH_FULL_IMAGE:figures/full_fig_p002_1.png] view at source ↗
Figure 3
Figure 3. Figure 3: a shows the pulse sequences used to measure T1 (top XY sequence) and T ∗ 2 (bottom XY sequence). To miti- [PITH_FULL_IMAGE:figures/full_fig_p003_3.png] view at source ↗
Figure 4
Figure 4. Figure 4: FIG. 4 [PITH_FULL_IMAGE:figures/full_fig_p004_4.png] view at source ↗
read the original abstract

Dissipation remains a central obstacle to improving superconducting quantum circuits, yet the microscopic origins of loss in widely used materials platforms are not fully understood. Here, we report the observation of interface piezoelectricity-induced dissipation in superconducting qubits fabricated on high-resistivity silicon. Our devices use a transmon qubit with a shunt capacitor that simultaneously serves as an interdigital transducer embedded in a surface acoustic wave resonator. By tuning the qubit transition into resonance with discrete mechanical modes, we observe up to a factor-of-two reduction in qubit lifetime, consistent with energy exchange between the qubit and mechanical modes mediated by piezoelectric coupling at the aluminum-silicon interface. Our findings provide direct evidence for interface piezoelectricity as a distinct loss channel in superconducting qubits. Combined with multiphysics simulations, these findings suggest that interface piezoelectric loss can dominate over loss from two-level systems at sufficiently high frequencies.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, simulated authors' rebuttal, and a circularity audit. Tearing a paper down is the easy half of reading it; the pith above is the substance, this is the friction.

Referee Report

2 major / 2 minor

Summary. The manuscript reports an experimental observation in superconducting transmon qubits fabricated on high-resistivity silicon, where the shunt capacitor doubles as an interdigital transducer in a surface acoustic wave resonator. Tuning the qubit transition frequency into resonance with discrete mechanical modes produces up to a factor-of-two reduction in qubit lifetime T1. The authors attribute this to energy exchange mediated by piezoelectric coupling at the aluminum-silicon interface, supported by multiphysics simulations indicating that interface piezoelectric loss can dominate over two-level system loss at sufficiently high frequencies. The central claim is that these findings provide direct evidence for interface piezoelectricity as a distinct loss channel.

Significance. If the attribution holds, the work identifies a new, potentially dominant loss mechanism in a common materials platform that could be engineered around in qubit design, particularly for higher-frequency operation. The device architecture that integrates the transmon capacitor with a SAW resonator is a clever experimental platform for probing mechanical loss channels. The combination of frequency-tuning data with multiphysics simulations to compare against TLS loss provides a quantitative angle that strengthens the interpretation if the simulations are fully validated.

major comments (2)
  1. [Results on frequency tuning and lifetime measurements] The claim of 'direct evidence' for interface piezoelectricity as the cause of the observed T1 reduction rests on the assumption that the lifetime dip arises specifically from piezo-mediated coupling to SAW modes rather than alternative mechanisms. However, the manuscript does not report extracted coupling rates g/2π from the resonance features or a quantitative comparison of these rates to the piezoelectric coefficient predicted by the multiphysics simulations. This comparison is load-bearing for ruling out fabrication variations, surface roughness changes, or frequency-dependent TLS density as the source of the resonant dips (see lifetime data and simulation discussion).
  2. [Experimental methods and discussion of alternative mechanisms] No control experiments are described that would suppress the piezoelectric effect (for example by modifying the Al-Si interface or IDT geometry) while preserving other device parameters to isolate its contribution. Without such controls or independent verification of the piezo coupling strength, the exclusion of other loss channels at mechanical resonances remains incomplete and weakens the central attribution.
minor comments (2)
  1. [Simulation section] The multiphysics simulation details, including the specific value of the piezoelectric coefficient used, mesh parameters, and boundary conditions at the interface, should be expanded or moved to the main text or supplementary information to allow readers to assess the claim that piezo loss dominates TLS at high frequencies.
  2. [Figure showing T1 vs. frequency] Clarify the statistical significance and error bars on the factor-of-two lifetime reduction across multiple devices and tuning sweeps to strengthen reproducibility.

Simulated Author's Rebuttal

2 responses · 0 unresolved

We thank the referee for their constructive feedback and for recognizing the potential significance of identifying interface piezoelectric loss in superconducting qubits. We address each major comment below with point-by-point responses and have revised the manuscript to strengthen the quantitative support for our claims where feasible.

read point-by-point responses

  1. Referee: [Results on frequency tuning and lifetime measurements] The claim of 'direct evidence' for interface piezoelectricity as the cause of the observed T1 reduction rests on the assumption that the lifetime dip arises specifically from piezo-mediated coupling to SAW modes rather than alternative mechanisms. However, the manuscript does not report extracted coupling rates g/2π from the resonance features or a quantitative comparison of these rates to the piezoelectric coefficient predicted by the multiphysics simulations. This comparison is load-bearing for ruling out fabrication variations, surface roughness changes, or frequency-dependent TLS density as the source of the resonant dips (see lifetime data and simulation discussion).

    Authors: We agree that a direct quantitative comparison of coupling rates would provide stronger evidence and help rule out alternatives. The original manuscript focused on the precise matching of observed resonance frequencies to simulated SAW modes and the overall consistency with multiphysics predictions of interface piezoelectric coupling. In the revised manuscript, we have added an analysis extracting effective coupling rates g/2π from the depth and width of the T1 dips using a model of resonant energy exchange between the qubit and mechanical modes. These extracted values (typically 1–8 MHz) are now directly compared to the piezoelectric coupling strengths computed in our simulations for the Al-Si interface, showing order-of-magnitude agreement with literature values for interface piezoelectric coefficients. This addition, including a new supplementary figure, strengthens the case against non-piezoelectric alternatives such as frequency-dependent TLS or fabrication artifacts, as those would not produce the observed mode-specific, frequency-selective behavior. revision: yes

  2. Referee: [Experimental methods and discussion of alternative mechanisms] No control experiments are described that would suppress the piezoelectric effect (for example by modifying the Al-Si interface or IDT geometry) while preserving other device parameters to isolate its contribution. Without such controls or independent verification of the piezo coupling strength, the exclusion of other loss channels at mechanical resonances remains incomplete and weakens the central attribution.

    Authors: We acknowledge that dedicated control experiments, such as interface modification or altered IDT geometries, would further isolate the piezoelectric contribution. However, implementing such controls while keeping all other device parameters (qubit frequency, coherence, resonator Q) identical requires a separate fabrication campaign with extensive process development, which exceeds the scope of the present study. In the revised manuscript, we have substantially expanded the discussion section to address alternative mechanisms in greater detail, including quantitative arguments why frequency-dependent TLS or surface roughness variations are inconsistent with the sharp, discrete resonances that align exactly with simulated SAW modes. We also reference independent literature values for Al-Si interface piezoelectricity as supporting verification and outline specific control experiments as promising directions for follow-up work. revision: partial

Circularity Check

0 steps flagged

Experimental observation of resonant lifetime reduction is independent of fitted inputs or self-referential definitions.

full rationale

The paper's central result is an experimental measurement: devices are fabricated with a transmon whose shunt capacitor doubles as an IDT in a SAW resonator, the qubit frequency is tuned across discrete mechanical resonances, and a factor-of-two drop in T1 is observed. This measured change is reported as direct evidence for interface piezoelectric coupling. No equations are presented that define a quantity in terms of itself or that rename a fitted parameter as a prediction. The multiphysics simulations are used only to suggest possible dominance over TLS loss at high frequency; they are not shown to be calibrated on the same lifetime data in a way that forces the conclusion. The attribution step is an interpretation, not a closed mathematical loop. No self-citation load-bearing steps or uniqueness theorems imported from prior author work appear in the reported chain. The result therefore remains self-contained against external benchmarks.

Axiom & Free-Parameter Ledger

0 free parameters · 2 axioms · 0 invented entities

The claim rests on the physical existence of piezoelectric coupling at the Al-Si interface and on the ability of multiphysics simulations to correctly predict the mechanical mode frequencies and coupling strengths; no new entities are postulated.

axioms (2)
  • domain assumption Piezoelectric effect exists at the aluminum-silicon interface in the fabricated devices
    Invoked when attributing lifetime reduction to energy exchange mediated by piezoelectric coupling
  • domain assumption Multiphysics simulations accurately model the mechanical modes and coupling
    Used to support that the observed loss is consistent with interface piezo rather than other mechanisms

pith-pipeline@v0.9.0 · 5700 in / 1305 out tokens · 37605 ms · 2026-05-20T19:44:33.060855+00:00 · methodology

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