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projects:quantum:seqnn [2026/05/21 07:12] – [Roadmap position] kymkiprojects:quantum:seqnn [2026/05/21 08:45] (current) – [Introduction] kymki
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-====== SEQNN Stage 5: Entangled Generative Estimation ======+====== Self-Estimating Quantum Neural Networks ======
  
-//Exploratory research note. This work is being shaped toward a publishable paper claim, but the results described here should be read as "work under validation".//+//Exploratory research note. This work is being shaped toward a publishable paper, but the results described here should be read as "work under validation". Github/codeberg link coming once I have had a strong coffee and cleaned up the repo.//
  
 ===== Introduction ===== ===== Introduction =====
  
-Kalman filters are fascinating. How can they be applied to QML models to provide some sort of "self-estimation" of state to be used in parameter updates? This was the fundamental question here that drove me to go on a rather extensive exploration of this topic. In this post I will describe the current position of Self-Estimating Quantum Neural Networks (SEQNN).+Kalman filtering is fascinating and has a wide area of application. How can it be applied to QML models to provide some sort of "self-estimation" of state? This was the fundamental question here that drove me to go on a rather extensive exploration of this topic. In this post I will describe the current position of Self-Estimating Quantum Neural Networks (SEQNN).
  
 SEQNN, is an attempt to treat the parameters of a variational quantum model as latent states to be estimated sequentially, rather than as weights managed by a global optimizer. SEQNN, is an attempt to treat the parameters of a variational quantum model as latent states to be estimated sequentially, rather than as weights managed by a global optimizer.
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   * each node maintains both an estimate and an uncertainty.   * each node maintains both an estimate and an uncertainty.
  
-The important difference is not only "which update rule is used." The claim being explored is structural: when the model is written as an estimator, uncertainty, identifiability, calibration, and measurement attribution become first-class objects instead of after-the-fact diagnostics.+The important difference is not only "which update rule is used." Rather, when the model is written as an estimator, uncertainty, identifiability, calibration, and measurement attribution become terms we can use to reason with and build our algorithms around. Is that helpful? Lets see what the outcome is here.
  
-===== Roadmap position =====+===== Roadmap position (needs improvements) =====
  
 ^ Stage ^ Status ^ ^ Stage ^ Status ^
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 $$ $$
  
-In a supervised classifier this can look like a covariance-aware optimizer. In the generative experiments, however, the measurements are actually sampled from a known latent quantum model. That is why the generative line is the cleaner foundation for publication claims about estimation, uncertainty, and calibration.+In a supervised classifier this can look like a covariance-aware optimizer. In the generative experiments, however, the measurements are actually sampled from a known latent quantum model.
  
 ===== Model ladder ===== ===== Model ladder =====
  
-The project deliberately moved through increasingly demanding observation models. The key pattern is: do not add parameters, entanglement, or topology until the observation equation says what can actually be observed.+The project moved through increasingly demanding observation models. The key pattern is: do not add parameters, entanglement, or topology until the observation equation says what can actually be observed.
  
 ^ Stage/model ^ Observation structure ^ What it tests ^ Claim status ^ ^ Stage/model ^ Observation structure ^ What it tests ^ Claim status ^
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 | Disjoint entangled ''RY+CNOT'' blocks | two-qubit CNOT blocks, but independent blocks | block attribution under entanglement | useful negative/diagnostic slice | | Disjoint entangled ''RY+CNOT'' blocks | two-qubit CNOT blocks, but independent blocks | block attribution under entanglement | useful negative/diagnostic slice |
 | Overlapping entangled ''RY+CNOT'' chain | nearest-neighbor factors share qubit parameters | distributed attribution through measurement factors | current Stage 5 publication target | | Overlapping entangled ''RY+CNOT'' chain | nearest-neighbor factors share qubit parameters | distributed attribution through measurement factors | current Stage 5 publication target |
- 
-===== Diagram: model progression ===== 
- 
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-<div style="max-width: 980px; margin: 1.2rem 0; padding: 1rem; border: 1px solid #d6dee8; background: #fbfcfe;"> 
-<svg xmlns="http://www.w3.org/2000/svg" viewBox="0 0 980 410" role="img" aria-label="SEQNN model progression from local RY to overlapping entangled RY CNOT chain" style="width: 100%; height: auto;"> 
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-  <text x="112" y="58" text-anchor="middle" font-family="Arial, sans-serif" font-size="16" font-weight="700" fill="#14395f">Stage 1</text> 
-  <text x="112" y="84" text-anchor="middle" font-family="Arial, sans-serif" font-size="14" fill="#14395f">local RY</text> 
-  <text x="112" y="108" text-anchor="middle" font-family="Arial, sans-serif" font-size="13" fill="#14395f">static recovery</text> 
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-  <circle cx="142" cy="128" r="8" fill="#2f6fae"></circle> 
- 
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-  <text x="328" y="58" text-anchor="middle" font-family="Arial, sans-serif" font-size="16" font-weight="700" fill="#1f5130">Stage 2</text> 
-  <text x="328" y="84" text-anchor="middle" font-family="Arial, sans-serif" font-size="14" fill="#1f5130">local RY</text> 
-  <text x="328" y="108" text-anchor="middle" font-family="Arial, sans-serif" font-size="13" fill="#1f5130">drift tracking</text> 
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- 
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-  <text x="544" y="58" text-anchor="middle" font-family="Arial, sans-serif" font-size="16" font-weight="700" fill="#6a4812">Stage 4</text> 
-  <text x="544" y="84" text-anchor="middle" font-family="Arial, sans-serif" font-size="14" fill="#6a4812">local RY+RZ</text> 
-  <text x="544" y="108" text-anchor="middle" font-family="Arial, sans-serif" font-size="13" fill="#6a4812">XYZ readout</text> 
-  <text x="544" y="130" text-anchor="middle" font-family="Arial, sans-serif" font-size="12" fill="#6a4812">identifiable phi</text> 
- 
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-  <text x="760" y="58" text-anchor="middle" font-family="Arial, sans-serif" font-size="16" font-weight="700" fill="#4d3372">Stage 5a</text> 
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-  <text x="760" y="108" text-anchor="middle" font-family="Arial, sans-serif" font-size="13" fill="#4d3372">diagnostic slice</text> 
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-  <text x="490" y="270" text-anchor="middle" font-family="Arial, sans-serif" font-size="18" font-weight="700" fill="#205b62">Current Stage 5 target</text> 
-  <text x="490" y="296" text-anchor="middle" font-family="Arial, sans-serif" font-size="15" fill="#205b62">overlapping RY+CNOT chain</text> 
-  <text x="490" y="320" text-anchor="middle" font-family="Arial, sans-serif" font-size="13" fill="#205b62">per-qubit EKFs plus Fisher-factor measurement updates</text> 
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-  <text x="382" y="383" text-anchor="middle" font-family="Arial, sans-serif" font-size="12" fill="#205b62">theta0</text> 
-  <text x="454" y="383" text-anchor="middle" font-family="Arial, sans-serif" font-size="12" fill="#205b62">theta1</text> 
-  <text x="526" y="383" text-anchor="middle" font-family="Arial, sans-serif" font-size="12" fill="#205b62">theta2</text> 
-  <text x="598" y="383" text-anchor="middle" font-family="Arial, sans-serif" font-size="12" fill="#205b62">theta3</text> 
- 
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-  <text x="806" y="198" font-family="Arial, sans-serif" font-size="13" fill="#455a64">disjoint blocks were not enough</text> 
-</svg> 
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 ===== The Stage 5 observation model ===== ===== The Stage 5 observation model =====
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 ===== Models compared in Stage 5 ===== ===== Models compared in Stage 5 =====
  
-^ Model ^ Role ^ State/covariance structure ^ What it tells us ^+^ Model ^ Role ^ State/covariance structure ^ What it explains ^
 | Adam | optimizer baseline | point estimate, no posterior covariance | whether a standard adaptive optimizer tracks the same sampled streams well | | Adam | optimizer baseline | point estimate, no posterior covariance | whether a standard adaptive optimizer tracks the same sampled streams well |
 | Gradient descent | optimizer baseline | point estimate, no posterior covariance | whether a tuned first-order method is enough | | Gradient descent | optimizer baseline | point estimate, no posterior covariance | whether a tuned first-order method is enough |
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 ===== What remains for the Stage 5 publication path ===== ===== What remains for the Stage 5 publication path =====
  
-The remaining work is about strengthening the evidence package, not changing the core idea.+The remaining work is about strengthening the evidence, not changing the core idea.
  
   - Decide whether to run a 50-seed sensitivity confirmation.   - Decide whether to run a 50-seed sensitivity confirmation.
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     * It helps show where distributed Fisher factors remain stable or attractive as the chain grows.     * It helps show where distributed Fisher factors remain stable or attractive as the chain grows.
  
-===== What we are not claiming yet =====+===== What I am not claiming =====
  
-This is important for the eventual paper framing. 
- 
-  * Not a quantum advantage claim. 
   * Not a hardware claim; these are controlled generative simulations.   * Not a hardware claim; these are controlled generative simulations.
   * Not an arbitrary-entangled-circuit claim.   * Not an arbitrary-entangled-circuit claim.
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   * Not a claim that every SEQNN variant works; the independent EKF is intentionally a negative control in Stage 5.   * Not a claim that every SEQNN variant works; the independent EKF is intentionally a negative control in Stage 5.
  
-The narrower claim is stronger:+Rather
  
 > In an identifiable overlapping entangled generative circuit, a distributed SEQNN estimator using Fisher/Jacobian-derived measurement-factor updates can track drifting quantum parameters from finite-shot observations, while preserving meaningful calibration diagnostics and outperforming standard optimizer baselines on the same sampled streams in the current validation regime. > In an identifiable overlapping entangled generative circuit, a distributed SEQNN estimator using Fisher/Jacobian-derived measurement-factor updates can track drifting quantum parameters from finite-shot observations, while preserving meaningful calibration diagnostics and outperforming standard optimizer baselines on the same sampled streams in the current validation regime.
  
-===== Publication framing ===== 
- 
-A good paper story is emerging: 
- 
-  - Start with the problem: VQC training usually treats circuit parameters as optimizer variables, not latent states. 
-  - Introduce SEQNN: local EKF estimators attached to quantum circuit parameters. 
-  - Distinguish supervised training from true generative estimation. 
-  - Show the model ladder from local identifiable circuits to richer local observations. 
-  - Use Stage 5 as the main contribution: entangled generative tracking through an overlapping measurement-factor graph. 
-  - Compare against Adam, GD, SPSA, independent SEQNN-EKF, and centralized EKF. 
-  - Be explicit that Fisher factors are the promoted distributed architecture. 
-  - Leave topology diffusion and augmented noise-state EKF as future work. 
- 
-The paper claim should be written as exploratory but concrete. The work is not finished because the scaling slice is still needed and the 50-seed sensitivity decision remains open. But Stage 5 now has a defensible center: the overlapping ''RY+CNOT'' chain shows why SEQNN is more than "EKF as another optimizer." It is a way to make the measurement model, the uncertainty, and the information flow part of the learning architecture itself. 
- 
-===== Suggested abstract-style summary ===== 
- 
-Self-Estimating Quantum Neural Networks frame variational quantum circuit training as sequential Bayesian estimation rather than global optimization. In the current generative benchmark line, circuit parameters are latent states, finite-shot measurements are observations, and each node maintains an Extended Kalman Filter over its local parameter uncertainty. We report exploratory Stage 5 results on an overlapping entangled ''RY+CNOT'' chain, where adjacent two-qubit measurement factors share qubit-owned parameters. A distributed Fisher-factor SEQNN estimator updates local qubit filters using Jacobian/Fisher information from the relevant measurement factors. This estimator is compared against Adam, gradient descent, SPSA, an independent per-node EKF control, and a centralized EKF reference on identical sampled streams. The current evidence supports the Fisher-factor estimator as the publication-focused Stage 5 architecture, while explicitly deferring broader topology-diffusion and augmented noise-state claims to future work.