Characterization of nested Walsh parity-check filters in a single-photon eight-mode register on a cloud photonic processor

• URL: http://arxiv.org/abs/2606.18408v2
• Date: Wed, 24 Jun 2026 21:54:22 GMT
• Title: Characterization of nested Walsh parity-check filters in a single-photon eight-mode register on a cloud photonic processor
• Abstract summary: We characterize two nested Walsh parity-check filters implemented on Quandela's Belenos cloud photonic processor.<n>Across more than 340,000 detections, neutral inputs show residual DC-port leakage of $0.02%$-$1.1%$.<n>A sector-preserving unitary core keeps leakage far below non-neutral controls over one to three applications.
• Score: 0.0
• License: http://arxiv.org/licenses/nonexclusive-distrib/1.0/
• Abstract: We characterize two nested Walsh parity-check filters implemented on Quandela's Belenos cloud photonic processor in a single-photon eight-mode spatial register. The modes are indexed by the vertices of the cube $Q_3$. The filters realize the classical $[8,7,2]$ single-parity-check code, the zero-sum neutral subspace $\mathcal{N}$ and the $[8,4,4]$ extended Hamming code, the parity-checked subspace $\mathcal{S}\subset\mathcal{N}$ with one DC and three face-parity syndrome channels. These are first-quantized path/mode encodings of classical codes: the experiment verifies leakage suppression and syndrome routing, not error correction or protection against photon loss, and all probabilities are conditional on postselected single-photon detections. Across more than 340,000 detections, neutral inputs show residual DC-port leakage of $0.02\%$-$1.1\%$ (mean $0.6\%$), corresponding to $\approx21\times$ suppression relative to the ideal $0.125$ DC-capture baseline and $31.6\times$ relative to the measured non-neutral control. Injected DC contamination gives a monotonic soft error signal, and the three face-parity syndrome channels route to their predicted ports with $94$-$99\%$ selectivity. A sector-preserving unitary core keeps leakage far below non-neutral controls over one to three applications, with differences dominated by calibration and compilation systematics rather than gate-cycle physics. We quantify these limits, including fixed-pattern separator bias, $\pm 0.02$ calibration offsets, and compilation scatter near the $10^{-3}$ leakage level, and report a Hong-Ou-Mandel degradation episode in which suppression vanished and recovered after recalibration.

Related papers

• A Single Fixed Shallow Circuit for Classical Shadows of Arbitrary n-Qubit States [2.5735476569508995]
  We construct a single fixed shallow quantum analyzer whose Born outcomes replace externally sampled settings as labels for reusable shadow snapshots.<n>The analyzer combines a freshly prepared $n$-qubit fiducial register $A$ with parallel Bell readout of $A$ and the unknown system $S$, producing one $2n$-bit record per copy.
  arXiv  Detail & Related papers  (2026-09-07T04:36:39Z)
• Fixed-order postselected CHSH reference acquisition for parity-constrained spatial-mode qubits on a commercial cloud photonic processor [0.0]
  We report a fixed-order Clauser-Horne-Shimony-Holt (CHSH) acquisition and reporting protocol for two encoded photonic qubits on Quandela's commercial, cloud-accessible Belenos processor.<n>Each logical qubit is a two-dimensional spatial-mode subspace in the seven-dimensional zero-sum sector of an eight-mode single-photon register.
  arXiv  Detail & Related papers  (2026-08-13T01:08:02Z)
• Round-Trip Consistency: Bidirectional Diffusion Models Can Predict Their Own Rollout Errors [51.56484100374058]
  Autoregressive models accumulate error over long rollouts, yet at deployment there is no ground truth to measure it against.<n>We train a single conditional latent diffusion model that steps a dynamical system forward or backward in time via a direction flag.<n>We show that this bidirectionality supplies a measurement-free test-time error signal.
  arXiv  Detail & Related papers  (2026-08-01T13:49:46Z)
• Level, Sharpness, and Corpus: Why Zero-Shot OOD Detector Rankings Do Not Transfer [36.02174685737611]
  We find that detector rankings reverse across deployments, every detector exceeds $80%$ FPR95 on at least one domain, and the preferred detector depends on both the in-distribution data and the underlying VLM.<n>We introduce the Complementary Evidence Guard (CEG), a detector-agnostic wrapper that preserves complementary evidence through a non-compensatory fusion of the base detector, level, and sharpness.
  arXiv  Detail & Related papers  (2026-07-29T08:00:49Z)
• Imbuing Large Language Models with Bidirectional Logic for Robust Chain Repair [44.80087038178069]
  We introduce Teleological Reasoning Infilling (TRI), a training framework that endows decoder-only transformers with a native emphgoal-conditioned bridging capability.<n>At inference, TRI operates as a surgical repair module within a dual-system loop.<n>Experiments on three benchmarks demonstrate that TRI achieves state-of-the-art performance across all tasks, while reducing per-problem token expenditure by 31.2%.
  arXiv  Detail & Related papers  (2026-06-03T15:58:48Z)
• The Security Budget of Code-LLM Prompt Hardening: Provable Limits Under Pass-Only Acceptance [0.0]
  We operationalize the floor as the emphTri-Audit Protocol, a two-axis reporting protocol that separates a prompt-side deductive registry attribute from a model-side empirical corollary.<n>A constrained best-of-family search over deterministic and guarded learned filters on CodeLlama-7B, Qwen2.5-Coder-7B/1.5B and DeepSeek-Coder-6.7B at $n=164$ yields the emphCross-Model Tri-Audit Invariance: of twenty-eight pass-preserving rows, twelve-changed-of-record learned-can
  arXiv  Detail & Related papers  (2026-06-02T08:22:14Z)
• Stochastic Estimation of the Layer-wise Hessian Trace for Monitoring Neural-network Training [45.88028371034407]
  We present a parameter estimator of the trace of the diagonal blocks of the Hessian matrix of the empirical risk of a neural network.<n>The procedure combines the Hutchinson trace estimator with a single Hessian-vector product over the whole parameter vector.<n>We show that correctness under weight sharing requires the layer-wise Hessian to be assembled before the second differentiation.
  arXiv  Detail & Related papers  (2026-05-25T10:24:32Z)
• Hidden-State Privacy Has an Empty Middle [51.56484100374058]
  We prove a complementary Fisher-ball lower bound: every full-rank Gaussian release at $O(1)$ Fisher utility admits a direction whose Mahalanobis signal grows linearly in hidden width.<n>A split-memory transformer trained from scratch reaches $G_mathrmMah in [20, 33]$ at 90M and maintains a $6$--$24times$ advantage over same-budget GPT baselines from 30M to 1B at a fixed-token language loss penalty.
  arXiv  Detail & Related papers  (2026-05-21T20:12:09Z)
• Hardware Validation of DAGI via a Modular "Ridge" Signature and High-Order Synergistic Information [0.0]
  DAGI (Directed Acyclic Graph Information) framework on IBM Quantum hardware.<n>Small, controlled experiment whose ideal output distribution is constrained to a low-dimensional modular manifold (a "ridge)<n>Key recovery exceeds chance: per-shot accuracy 0.1689 (chance 0.125, 95% Wilson CI [0.1610, 0.1772])<n>These results support the claim that DAGI detects and quantifies non-trivial, hardware-resilient information structure.
  arXiv  Detail & Related papers  (2026-04-16T14:16:59Z)
• Strip-Symmetric Quantum Codes for Biased Noise: Z-Decoupling in Stabilizer and Floquet Codes [5.685589351789461]
  Bias-tailored codes such as the XZZX surface code and the domain wall color code achieve high dephasing-biased thresholds.<n>We define strip-symmetric biased codes, a class of static stabilizer and dynamical (Floquet) codes for which, under pure dephasing and perfect measurements, each elementary $Z$ fault is confined to a strip and the Z-detector--fault incidence matrix is block diagonal.<n>For such codes the Z-detector hypergraph decomposes into independent strip components and maximum-likelihood $Z$ decoding factorizes across strips, yielding complexity savings for
  arXiv  Detail & Related papers  (2026-01-07T06:06:20Z)
• Burau representation, Squier's form, and non-Abelian anyons [53.92822954974537]
  We introduce a frequency-tunable, two-dimensional non-Abelian control of operation order constructed from the Burau representation of the braid group $B_3$.<n>The sign change of $Delta(omega)$ across the Squier positivity window reveals alternating constructive and destructive interference of causal orders.<n> Numerical simulations confirm both enhancement and suppression regimes, establishing a minimal $B_3$ braid control.
  arXiv  Detail & Related papers  (2025-10-21T00:25:21Z)
• Reinforcement Learning with Verifiable yet Noisy Rewards under Imperfect Verifiers [90.50039419576807]
  Reinforcement Learning with Verifiable Rewards (RLVR) trains policies against automated verifiers to avoid costly human labeling.<n>To reduce vulnerability to verifier hacking, many RLVR systems collapse rewards to binary $0,1$ during training.<n>This choice carries a cost: it introduces textitfalse negatives (rejecting correct answers, FNs) and textitfalse positives (accepting incorrect ones, FPs)
  arXiv  Detail & Related papers  (2025-10-01T13:56:44Z)
• SplashNet: Split-and-Share Encoders for Accurate and Efficient Typing with Surface Electromyography [3.3640830721676003]
  Surface electromyography (sEMG) at the wrists could enable natural, keyboard-free text entry.<n>State-of-the-art emg2qwerty baseline still misrecognizes $51.8%$ of characters in the zero-shot setting on unseen users.<n>We trace many of these errors to mismatched cross-user signal statistics.
  arXiv  Detail & Related papers  (2025-06-14T05:38:29Z)
• Far from Perfect: Quantum Error Correction with (Hyperinvariant) Evenbly Codes [38.729065908701585]
  We introduce a new class of qubit codes that we call Evenbly codes.<n>Our work indicates that Evenbly codes may show promise for practical quantum computing applications.
  arXiv  Detail & Related papers  (2024-07-16T17:18:13Z)
• Corruption-Robust Offline Reinforcement Learning with General Function Approximation [60.91257031278004]
  We investigate the problem of corruption in offline reinforcement learning (RL) with general function approximation. Our goal is to find a policy that is robust to such corruption and minimizes the suboptimality gap with respect to the optimal policy for the uncorrupted Markov decision processes (MDPs)
  arXiv  Detail & Related papers  (2023-10-23T04:07:26Z)
• Minimum optical depth multiport interferometers for approximating arbitrary unitary operations and pure states [37.69303106863453]
  We address the problem of, using multiport interferometers, approximating with a given infidelity any pure state preparation and any unitary operation.<n>By means of numerical calculations, we show that pure states, in any dimension $d$, can be prepared with infidelity.
  arXiv  Detail & Related papers  (2020-02-04T15:40:49Z)

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.