Pepsy Library

pepsy is a Python package for circuit simulation and related DMRG fitting workflows.

Current package version: 0.2.0 (from pyproject.toml / pepsy.__version__).

Package Layout

• src/pepsy/: installable library code
  • backends/: backend selection, conversion, and linear algebra registration
  • tensors/: lattice maps (OneDMap), state/MPO/PEPO builders, contraction helpers
  • operators/: gates, gate application, MPO/PEPO builders, and Hamiltonian helpers
  • boundary/: boundary state initialization (BdyMPS), sweeps (CompBdy), and metrics
  • solvers/: gradient-based and finite-difference solvers
  • fitting/: local tensor fitting routines (FIT)
  • optimizers/: sweep, global, energy, MPS, and MPO optimizers
  • sampling/: MpsSampler and related sampling utilities
  • _internal/: private formatting and utility helpers
• examples/: runnable examples (e.g. MpsMagnetization/ 2D ITF Trotter MPS evolution)
• docs/: Sphinx documentation source
• tests/: package tests

Install

pip install -U --no-deps -e .
# Optional backends:
# pip install -e .[torch]
# pip install -e .[solvers]
# jax backend (manual, platform-specific wheels):
# pip install jax jaxlib
# Optional plotting helpers:
# pip install -e .[viz]

Quick Usage

import pepsy
import quimb.tensor as qtn

ket = qtn.PEPS.rand(Lx=3, Ly=3, bond_dim=2, seed=1, dtype="complex128")
ket_tagged, norm = pepsy.build_bra_ket(ket=ket)

bdy = pepsy.BdyMPS(tn_flat=ket_tagged, tn_double=norm, chi=32, single_layer=False)
res = pepsy.contract_boundary(norm=norm, bdy=bdy, direction="y", n_iter=2)

print(pepsy.__version__, res.cost)

Documentation

Build docs locally:

pip install -e .[docs]
NUMBA_CACHE_DIR=/tmp PYTHONPYCACHEPREFIX=/tmp \
sphinx-build -W -b html docs docs/_build/html

Main docs sections:

• getting_started
• tutorials/
• howto/
• api/

Notes

• .gitattributes marks notebooks as binary to avoid noisy diffs.
• .gitignore excludes checkpoints, caches, cash/, and nohup.out.