README.md

---
license: apache-2.0
pipeline_tag: tabular-regression
datasets:
- Allanatrix/QST
tags:
- Physics
---
# NexaQST: Quantum State Tomography with Physics-Informed Neural Networks

**NexaQST** is a Quantum State Tomography model built using a Physics-Informed Neural Network (PINN) trained on synthetic 2-qubit experiments. This model leverages quantum mechanical priors such as positivity, Hermiticity, and trace constraints to ensure physically plausible reconstructions of quantum states.

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## Model Overview

- **Task**: Reconstruct quantum states (density matrices) from tomographic measurement traces
- **System**: Simulated 2-qubit experiments
- **Architecture**: Physics-Informed Neural Network (PINN)
- **Constraints Embedded**:
  - Positivity
  - Hermiticity
  - Trace normalization (Tr(ρ) = 1)

---

## Dataset Generation

- **Simulation Toolkit**: [`QuTiP`](https://qutip.org/)
- **Process**:
  1. Generated full 2-qubit tomography experiments via simulation
  2. Extracted and structured measurement traces
  3. Derived backward synthetic traces from known density matrices
  4. Created supervised training pairs: `(trace → density matrix)`
  5. Enforced physical constraints directly inside the model during training

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## Model Input/Output

- **Input**: Vector of tomographic measurement traces
- **Output**: Reconstructed density matrix (complex-valued 4x4 for 2 qubits)

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## Example Usage

```python
# Pseudocode for usage

from model import NexaQSTModel
import torch

model = NexaQSTModel()
model.load_state_dict(torch.load("nexaqst_model.pt"))
model.eval()

traces = load_measurement_vector("qst_trace.npy")  # shape: (N,)
rho_pred = model.predict_density_matrix(traces)

# rho_pred is a 4x4 complex-valued matrix satisfying physical constraints
````

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## Applications

* Quantum error correction diagnostics
* Quantum system identification
* Educational simulation of QST techniques
* Physically consistent state estimation for quantum simulations

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## Licensing & Citation

* If used in publications or products, please credit the Nexa Scientific Suite.

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## 🌐 Related Tools

* [📁 Nexa Data Studio](https://huggingface.co/spaces/Allanatrix/NexaDataStudio)
* [🔬 Nexa R\&D Hub](https://huggingface.co/spaces/Allanatrix/NexaR&D)
* [🧠 Nexa MOE Models](https://huggingface.co/collections/Allanatrix/nexa-models)
* [🌐 Nexa Hub (Main Portal)](https://huggingface.co/spaces/Allanatrix/NexaHub)

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*Created by [Allan](https://huggingface.co/Allanatrix), independent quantum systems architect and ML researcher. Part of the Nexa scientific computing ecosystem.*