NexaQST

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)

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Dataset Generation

• Simulation Toolkit: QuTiP
• 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

# 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
• 🔬 Nexa R&D Hub
• 🧠 Nexa MOE Models
• 🌐 Nexa Hub (Main Portal)

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Created by Allan, independent quantum systems architect and ML researcher. Part of the Nexa scientific computing ecosystem.