qiskit-data-reuploading

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Authors

This library is developed and maintained by:

Name	Affiliation	Contact
Carlos A. Durán Paredes	Corporation for Aerospace Initiatives, Research and Innovation (CASIRI), Popayán, Colombia	caduranpd@gmail.com
Javier E. León Calderón	Department of Electronics Engineering, Universidad Nacional de Colombia, Manizales, Colombia	javleonca@unal.edu.co
Nicolás Sánchez Perea	Department of Electronics Engineering, Universidad del Cauca, Popayán, Colombia	nicolassp@unicauca.edu.co
German Darío Díaz	Department of Physics, Universidad del Cauca, Popayán, Colombia	germandiaz@unicauca.edu.co
Camilo Segura	Corporation for Aerospace Initiatives, Research and Innovation (CASIRI), Popayán, Colombia	camilosegura6@gmail.com

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Table of Contents

• What is Data Re-uploading?
• Existing Ecosystem Analysis
• Installation
• Quick Start
• API Overview
• Architecture
• Supported Versions
• Hardware Integration
• Benchmarking
• Scientific Background
• Licensing
• Citation
• Contributing
• Disclaimer

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What is Data Re-uploading?

Classical machine learning encodes data once before processing it. Data re-uploading breaks this assumption: input features are injected at every layer of the quantum circuit, interleaved with trainable rotation gates.

Layer 1:  [ Encode(x) → Train(θ) ]
Layer 2:  [ Encode(x) → Train(θ) ] ← same x, new θ
Layer N:  [ Encode(x) → Train(θ) ]
               ↓
          Measure → classify

A single qubit with enough layers can approximate any continuous function — a quantum analog of the universal approximation theorem. This makes it a uniquely compact variational model for NISQ hardware.

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Existing Ecosystem Analysis

This library addresses a gap that remained open in the Qiskit ecosystem as of mid-2025:

What exists	Framework	Status
PR #668 "Implement Data-reuploading classifier"	qiskit-machine-learning	DRAFT, abandoned ~2024, never merged
Data-reuploading tutorial	PennyLane	Maintained demo — not a library
Academic Qiskit notebook (arXiv:2211.13191)	Qiskit 1.x	Didactic, no pip install, legacy APIs

What did not exist before this library:

• A pip-installable DataReuploadingClassifier with sklearn-compatible API
• Native data re-uploading support in qiskit-machine-learning
• A dedicated feature map in Qiskit's circuit.library
• Reproducible benchmarks (DR vs. MLP/SVM) on Qiskit 2.x V2 primitives

Deprecated approaches this library explicitly avoids:

• execute() and Aer.get_backend() — removed in Qiskit 2.x
• V1 primitives (StatevectorSimulator, algorithm_globals)
• BlueprintCircuit — deprecated upstream in favor of constructor methods

This library uses exclusively V2 primitives: StatevectorEstimator, StatevectorSampler for local simulation, and qiskit_ibm_runtime.EstimatorV2 for IBM Quantum hardware.

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Installation

Standard:

pip install qiskit-data-reuploading

With IBM Quantum hardware support:

pip install "qiskit-data-reuploading[hardware]"

From source (latest development):

git clone https://github.com/Carlosandp/qiskit-data-reuploading.git
cd qiskit-data-reuploading
pip install -e ".[dev]"

Requirements: Python ≥ 3.10 · Qiskit ≥ 2.0 · qiskit-machine-learning ≥ 0.9.0 · qiskit-aer ≥ 0.15

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Quick Start

Classification

from sklearn.datasets import load_iris
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import MinMaxScaler
from qdr.models import DataReuploadingClassifier

X, y = load_iris(return_X_y=True)
X = MinMaxScaler().fit_transform(X)
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2)

model = DataReuploadingClassifier(
    n_qubits=2,
    n_layers=5,
    encoding="rx_ry_rz",    # "rx" | "ry" | "rz" | "rx_ry_rz"
    entanglement="full",     # "none" | "linear" | "circular" | "full"
    optimizer="COBYLA",      # "COBYLA" | "SPSA" | "ADAM"
    backend=None,            # None → StatevectorEstimator (local, exact)
    shots=None,              # None → exact; int → noisy simulation
    max_iter=150,
)

model.fit(X_train, y_train)

preds  = model.predict(X_test)
proba  = model.predict_proba(X_test)
score  = model.score(X_test, y_test)

print(f"Accuracy: {score:.4f}")

model.save("iris_model.pkl")
loaded = DataReuploadingClassifier.load("iris_model.pkl")

Circuit inspection

from qdr.circuits import DataReuploadingCircuit

circuit = DataReuploadingCircuit(n_qubits=2, n_layers=3, n_features=4)
circuit.build_circuit()
circuit.draw("mpl")           # matplotlib figure
circuit.draw("text")          # ASCII
print(circuit.get_parameters())

Benchmarking against classical baselines

from qdr.benchmarks import BenchmarkRunner
from sklearn.datasets import make_moons

X, y = make_moons(n_samples=200, noise=0.1)

runner = BenchmarkRunner(cv_folds=5)
runner.run(X, y, include_svm=True, include_mlp=True, include_lr=True)

df = runner.summary()
# Returns pandas DataFrame: model, accuracy, f1, precision, recall, mcc, train_time_s
print(df.to_string(index=False))

Visualization

from qdr.visualization import (
    plot_decision_boundary,
    plot_loss_curve,
    plot_bloch_trajectory,
    plot_parameter_landscape,
)

plot_loss_curve(model.loss_history_)
plot_decision_boundary(model, X_test, y_test)
plot_bloch_trajectory(circuit, X_train[0])

IBM Quantum hardware

from qdr.hardware import run_on_ibm_backend

result = run_on_ibm_backend(
    model=model,
    X=X_test,
    backend_name="ibm_brisbane",   # or "fake_manila" for noise simulation
    shots=1024,
)

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API Overview

Class / Function	Module	Description
DataReuploadingClassifier	qdr.models	sklearn-compatible multi-class classifier
DataReuploadingRegressor	qdr.models	sklearn-compatible regressor
DataReuploadingCircuit	qdr.circuits	parameterized re-uploading circuit
ReuploadingFeatureMap	qdr.circuits	fixed-weight feature map (no training)
ParameterShiftGradient	qdr.training	exact quantum gradients via parameter shift
SPSA	qdr.training	gradient-free stochastic optimizer
COBYLA	qdr.training	derivative-free local optimizer
ADAM	qdr.training	adaptive moment estimation optimizer
BenchmarkRunner	qdr.benchmarks	benchmarks vs. MLP, SVM, logistic regression
plot_decision_boundary	qdr.visualization	2D decision boundary plot
plot_loss_curve	qdr.visualization	training loss over iterations
plot_bloch_trajectory	qdr.visualization	qubit state on Bloch sphere per layer
plot_parameter_landscape	qdr.visualization	2D cost landscape scan
run_on_ibm_backend	qdr.hardware	execution on IBM Quantum real hardware

Full API documentation: docs/api/

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Architecture

qdr/
├── circuits/
│   ├── data_reuploading.py     # DataReuploadingCircuit
│   └── feature_maps.py         # ReuploadingFeatureMap
├── models/
│   ├── classifier.py           # DataReuploadingClassifier
│   └── regressor.py            # DataReuploadingRegressor
├── training/
│   ├── gradients.py            # ParameterShiftGradient
│   └── optimizers.py           # SPSA, COBYLA, ADAM wrappers
├── benchmarks/
│   └── runner.py               # BenchmarkRunner
├── visualization/
│   └── plots.py                # all plotting utilities
├── hardware/
│   └── ibm_backend.py          # IBM Quantum integration (V2 Runtime)
└── utils/
    └── encoding.py             # RX/RY/RZ encoding helpers

All modules are independent. No circular imports. Each subpackage can be used in isolation without loading the full library.

---

Supported Versions

Python	Qiskit	qiskit-machine-learning	qiskit-aer
3.10	≥ 2.0	≥ 0.9.0	≥ 0.15
3.11	≥ 2.0	≥ 0.9.0	≥ 0.15
3.12	≥ 2.0	≥ 0.9.0	≥ 0.15
3.13	≥ 2.0	≥ 0.9.0	≥ 0.15

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Hardware Integration

The library supports three execution modes:

Mode	Backend	Noise	Use case
Exact simulation	StatevectorEstimator	None	Development, small circuits
Noisy simulation	AerSimulator + noise model	Configurable	Pre-hardware testing
Real hardware	qiskit_ibm_runtime.EstimatorV2	Device noise	Production experiments

All modes share the same API — switching is a single backend= argument.

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Benchmarking

BenchmarkRunner evaluates models using stratified k-fold cross-validation and reports: accuracy, F1-score (macro), precision, recall, MCC, and training time.

Supported datasets out of the box: Iris, Moons, Circles, Wine, reduced MNIST.

Baselines: sklearn MLP, SVM (RBF kernel), and Logistic Regression.

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Scientific Background

This library implements the data re-uploading technique introduced in:

Pérez-Salinas, A., Cervera-Lierta, A., Gil-Fuster, E., & Latorre, J.I. (2020). Data re-uploading for a universal quantum classifier. Quantum, 4, 226. https://doi.org/10.22331/q-2020-02-06-226

Key result from the paper: A single-qubit circuit with re-uploading layers can approximate any continuous function on a compact domain, making it a universal classifier with minimal qubit overhead. Entanglement across multiple qubits extends this expressibility with improved sample efficiency.

Implementation notes:

• Encoding and trainable parameters are kept strictly separate in the circuit
• Parameter shift rules compute exact gradients without finite-difference approximation
• Barren plateau risk is discussed in docs/barren_plateaus.md
• Scalability is limited by current NISQ hardware; see docs/nisq_limitations.md

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Licensing

This project uses a dual license:

Component	License
Source code (qdr/, tests/, examples/)	MIT License
Documentation, notebooks, tutorials (docs/, notebooks/)	CC BY 4.0

What this means in practice:

• You can use, modify, and redistribute the code freely under MIT terms.
• If you reuse or adapt the documentation or notebooks, you must credit the author.
• Academic publications using this library should include the citation below.

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Citation

If you use this library in research or academic work, please cite both the original paper and this software. If your work involves UAV anomaly detection or the QML benchmark evaluation, also cite the associated study below.

Original method:

@article{perez2020data,
  title     = {Data re-uploading for a universal quantum classifier},
  author    = {P{\'{e}}rez-Salinas, Adri{\'{a}}n and Cervera-Lierta, Alba
               and Gil-Fuster, Elies and Latorre, Jos{\'{e}} Ignacio},
  journal   = {Quantum},
  volume    = {4},
  pages     = {226},
  year      = {2020},
  doi       = {10.22331/q-2020-02-06-226},
  url       = {https://doi.org/10.22331/q-2020-02-06-226}
}

This software:

@software{duranleon2026qdr,
  title     = {qiskit-data-reuploading: A pip-installable sklearn-compatible library
               for data re-uploading quantum classifiers on Qiskit 2.x},
  author    = {Carlos Andr{\'e}s Dur{\'a}n Paredes and
               Javier Esteban Le{\'o}n Calder{\'o}n and
               Nicol{\'a}s S{\'a}nchez Perea and
               German Dar{\'i}o D{\'i}az and
               Camilo Segura},
  year      = {2026},
  url       = {https://github.com/Carlosandp/qiskit-data-reuploading},
  license   = {MIT (code) / CC BY 4.0 (docs)},
  note      = {Compatible with Qiskit 2.x. Not affiliated with IBM.}
}

Associated study — UAV anomaly detection benchmark:

@article{duran2026qml,
  title     = {Quantum Machine Learning for Cyber-Physical Anomaly Detection in
               Unmanned Aerial Vehicles: A Leakage-Free Evaluation with
               Proxy-Audited Feature Sets},
  author    = {Dur{\'a}n Paredes, Carlos A. and
               Le{\'o}n Calder{\'o}n, Javier E. and
               S{\'a}nchez Perea, Nicol{\'a}s and
               D{\'i}az, German Dar{\'i}o and
               Segura Quintero, Camilo},
  year      = {2026},
  eprint    = {2605.19233},
  archivePrefix = {arXiv},
  primaryClass  = {cs.CR},
  doi       = {10.48550/arXiv.2605.19233},
  url       = {https://arxiv.org/abs/2605.19233},
  note      = {10 pages, 7 figures, 1 table; open Qiskit 2.x implementation
               available at https://github.com/Carlosandp/qiskit-data-reuploading}
}

Preprint: Durán Paredes et al. (2026). Quantum Machine Learning for Cyber-Physical Anomaly Detection in Unmanned Aerial Vehicles: A Leakage-Free Evaluation with Proxy-Audited Feature Sets. arXiv:2605.19233 [cs.CR]. https://arxiv.org/abs/2605.19233

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Contributing

Contributions are welcome. See CONTRIBUTING.md for guidelines.

Priority areas:

• Additional encoding schemes (ZZ, Pauli, custom)
• Noise-aware training methods
• Hardware experiment results and calibration data
• Additional benchmark datasets
• Contributions toward a potential upstream PR to qiskit-machine-learning

Before opening a PR, run the test suite:

pytest tests/ --cov=qdr --cov-report=term-missing

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Disclaimer

This project is compatible with Qiskit but is not affiliated with, endorsed by, or maintained by IBM. Qiskit is a registered trademark of IBM. The use of Qiskit in this project's name and documentation is solely to indicate technical compatibility.