A Preparation Nonstationarity Loophole in Superconducting-Qubit Bell Tests

• URL: http://arxiv.org/abs/2601.08290v1
• Date: Tue, 13 Jan 2026 07:31:00 GMT
• Title: A Preparation Nonstationarity Loophole in Superconducting-Qubit Bell Tests
• Authors: Prosanta Pal, Shubhanshu Karoliya, Gargee Sharma, Ramakrishna Podila,
• Abstract summary: We show that the assumption that repeated circuit executions sample a single, stationary preparation ensemble can be violated on contemporary hardware.<n>We introduce an ensemble-divergence framework in which slow temporal drift of the preparation process induces context-dependent effective ensembles.<n>Our results identify a preparation-dependent loophole relevant to Bell tests on noisy intermediate-scale quantum devices.
• Score: 0.0
• License: http://creativecommons.org/licenses/by/4.0/
• Abstract: Bell or Clauser-Horne-Shimony-Holt (CHSH) tests on superconducting quantum processors are commonly interpreted under the assumption that repeated circuit executions sample a single, stationary preparation ensemble. Here we show that this assumption can be violated on contemporary hardware, with direct implications for the interpretation of observed Bell violations. We introduce an ensemble-divergence framework in which slow temporal drift of the preparation process induces context-dependent effective ensembles, even when measurement independence and locality are preserved. This leads to a relaxed Bell bound $|S| \le 2 + 6δ_{\mathrm{ens}}$, where $δ_{\mathrm{ens}}$ quantifies preparation nonstationarity. Because $δ_{\mathrm{ens}}$ is not directly observable, we develop an operational witness $δ_{\mathrm{op}}$ based on bin-resolved outcome statistics for fixed measurement channels. Using Pauli-axis measurements on IBM superconducting processors, we observe statistically significant operational drift that persists after full two-qubit readout mitigation, ruling out measurement artifacts. In contrast, drift extracted from CHSH-optimal measurements is eliminated by mitigation, demonstrating that such settings are unsuitable for diagnosing preparation nonstationarity. We further show that the observed Bell violations imply only modest ensemble divergences, comparable in scale to those required in Hall-type measurement-dependence models, but arising here solely from preparation drift combined with experimental scheduling. Our results identify a preparation-dependent loophole relevant to Bell tests on noisy intermediate-scale quantum devices and highlight the necessity of drift-aware protocols for reliable quantum certification.

Related papers

• Sharp Convergence Rates for Masked Diffusion Models [53.117058231393834]
  We develop a total-variation based analysis for the Euler method that overcomes limitations.<n>Our results relax assumptions on score estimation, improve parameter dependencies, and establish convergence guarantees.<n>Overall, our analysis introduces a direct TV-based error decomposition along the CTMC trajectory and a decoupling-based path-wise analysis for FHS.
  arXiv  Detail & Related papers  (2026-02-26T00:47:51Z)
• Information Fidelity in Tool-Using LLM Agents: A Martingale Analysis of the Model Context Protocol [69.11739400975445]
  We introduce the first theoretical framework for analyzing error accumulation in Model Context Protocol (MCP) agents.<n>We show that cumulative distortion exhibits linear growth and high-probability deviations bounded by $O(sqrtT)$.<n>Key findings include: semantic weighting reduces distortion by 80%, and periodic re-grounding approximately every 9 steps suffices for error control.
  arXiv  Detail & Related papers  (2026-02-10T21:08:53Z)
• Bell-Inequality Violation for Continuous, Non-Projective Measurements [1.5755923640031846]
  We show that Bell-CHSH inequality violation can be extracted from continuous, non-projective measurements.<n>We benchmark the resulting estimator against conventional projective-measurement CHSH tests.<n>Our results provide a practical route to demonstrating Bell nonlocality in platforms where measurements are inherently continuous and weak.
  arXiv  Detail & Related papers  (2025-12-23T03:58:54Z)
• Quantum Nonlocality and Device-Independent Randomness Robust to Relaxations of Bell Assumptions [4.183295888979239]
  We show that states of constant local dimension $d$ are sufficient to certify quantum nonlocality under arbitrary MI and PI relaxation.<n>We introduce the notion of textitmeasurement-dependent locality as the set of input-output behaviors under simultaneous relaxations of measurement and independence.<n>We analytically derive the quantum guessing probability for one player's outcomes in the CHSH Bell test.
  arXiv  Detail & Related papers  (2025-12-20T21:20:18Z)
• Experimental Demonstration of the PBR Test on a Superconducting Processor [0.0]
  We present an experimental implementation of the Pusey-Barrett-Rudolph (PBR) no-go theorem on IBM's 156-qubit Heron2 Marrakesh quantum processor.
  arXiv  Detail & Related papers  (2025-10-13T09:46:52Z)
• Certifying classes of $d$-outcome measurements with quantum steering [49.1574468325115]
  We provide a construction of a family of steering inequalities tailored to large classes of $d$-outcomes projective measurements. We prove that the maximal quantum violation of those inequalities can be used for certification of those measurements and the maximally entangled state of two qudits.
  arXiv  Detail & Related papers  (2024-10-27T15:32:53Z)
• Relaxed Quantile Regression: Prediction Intervals for Asymmetric Noise [51.87307904567702]
  Quantile regression is a leading approach for obtaining such intervals via the empirical estimation of quantiles in the distribution of outputs.<n>We propose Relaxed Quantile Regression (RQR), a direct alternative to quantile regression based interval construction that removes this arbitrary constraint.<n>We demonstrate that this added flexibility results in intervals with an improvement in desirable qualities.
  arXiv  Detail & Related papers  (2024-06-05T13:36:38Z)
• An Efficient Rehearsal Scheme for Catastrophic Forgetting Mitigation during Multi-stage Fine-tuning [55.467047686093025]
  A common approach to alleviate such forgetting is to rehearse samples from prior tasks during fine-tuning.<n>We propose a sampling scheme, textttbf mix-cd, that prioritizes rehearsal of collateral damage'' samples.<n>Our approach is computationally efficient, easy to implement, and outperforms several leading continual learning methods in compute-constrained settings.
  arXiv  Detail & Related papers  (2024-02-12T22:32:12Z)
• Device-independent certification of desirable properties with a confidence interval [0.0]
  We provide a versatile solution for rigorous device-independent certification. We show how the PBR protocol and the martingale-based protocol often offer similar performance. Our findings also show that the performance of the martingale-based protocol may be severely affected by one's choice of the witness.
  arXiv  Detail & Related papers  (2024-01-12T15:21:21Z)
• Device-independent self-testing of unsharp measurements [0.0]
  Semi-device-independent certification of an unsharp instrument has recently been demonstrated. We provide device-independent (DI) self-testing of the unsharp instrument through the quantum violation of two Bell inequalities.
  arXiv  Detail & Related papers  (2023-11-08T06:34:47Z)
• Correcting for finite statistics effects in a quantum steering experiment [33.013102271622614]
  We introduce a one-sided device-independent protocol that corrects for apparent signaling effects in experimental probability distributions.<n>Our results show a significantly higher probability of violation than existing state-of-the-art inequalities.<n>This work demonstrates the power of semidefinite programming for entanglement verification and brings quantum networks closer to practical applications.
  arXiv  Detail & Related papers  (2023-05-23T14:39:08Z)
• Importance sampling for stochastic quantum simulations [68.8204255655161]
  We introduce the qDrift protocol, which builds random product formulas by sampling from the Hamiltonian according to the coefficients. We show that the simulation cost can be reduced while achieving the same accuracy, by considering the individual simulation cost during the sampling stage. Results are confirmed by numerical simulations performed on a lattice nuclear effective field theory.
  arXiv  Detail & Related papers  (2022-12-12T15:06:32Z)
• Robust PAC$^m$: Training Ensemble Models Under Misspecification and Outliers [46.38465729190199]
  PAC-Bayes theory demonstrates that the free energy criterion minimized by Bayesian learning is a bound on the generalization error for Gibbs predictors. This work presents a novel robust free energy criterion that combines the generalized score function with PAC$m$ ensemble bounds.
  arXiv  Detail & Related papers  (2022-03-03T17:11:07Z)
• Ab-initio experimental violation of Bell inequalities [0.9786690381850356]
  violation of a Bell inequality is the paradigmatic example of device-independent quantum information. In practice, all Bell experiments rely on the precise understanding of the underlying physical mechanisms. We propose and experimentally implement a solution to this ab-initio task. Treating preparation and measurement devices as black-boxes, and relying on the observed statistics only, our adaptive protocol approaches the optimal Bell inequality violation.
  arXiv  Detail & Related papers  (2021-08-02T00:39:52Z)

This list is automatically generated from the titles and abstracts of the papers in this site.

This site does not guarantee the quality of this site (including all information) and is not responsible for any consequences.