Quantax

Flexible and scalable neural quantum states built on JAX

📖 Documentation

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🔍Scope

Quantax is a research-oriented Python package for quantum many-body physics, with a focus on flexible and scalable neural quantum states (NQS). Apart from NQS, Quantax also includes several useful techniques in variational Monte Carlo (VMC):

• Exact diagonalization and small-system benchmarks via QuSpin
• Fermionic mean-field wavefunctions
• Flexible (neural) wavefunction design via Equinox
• Tensor networks via quimb and symmray (to be implemented)

⚙️Installation

Requires Python 3.10+, JAX 0.6.1+

First, ensure that a correct JAX version is installed. For details, check JAX Installation.

For a direct installation of full functionality (recommended in most cases),

pip install quantax[full]

For a minimal installation,

pip install quantax

🚀Quick Start

import quantax as qtx
import matplotlib.pyplot as plt

# Define a spin chain with 8 spins, stored as a global object in quantax
lattice = qtx.sites.Chain(L=8)

# Ising hamiltonian with transverse field h=1
H = qtx.operator.Ising(h=1)

# Exact diagonalization
E, wf = H.diagonalize()

# RBM wavefunction with 16 hidden units
model = qtx.model.RBM_Dense(features=16)

# Construct variational state
state = qtx.state.Variational(model)

# Sampler with local flip updates
sampler = qtx.sampler.LocalFlip(state, nsamples=64)

# Stochastic reconfiguration optimizer
optimizer = qtx.optimizer.SR(state, H)

energy_data = qtx.utils.DataTracer()
for i in range(100):
    samples = sampler.sweep()
    step = optimizer.get_step(samples)
    state.update(step * 1e-2)
    energy_data.append(optimizer.energy)

energy_data.plot(baseline=E)
plt.show()