itensor-linear-rotors

An ITensor SiteSet for linear rotors.

Configuration

The Makefile assumes that you have the following standard environment variables set:

• CPATH should contain the path to the ITensor root directory.
• LIBRARY_PATH should contain the path to ITensor's lib directory.

Additionally, the options chosen in ITensor's options.mk file will determine the values needed in the following environment variables:

• ITENSOR_CXX should be set to the compiler used to build ITensor (likely g++ or clang++).
• ITENSOR_CXXFLAGS should be set to the list of compiler flags needed by ITensor (for example, -std=c++17 -DPLATFORM_openblas)
• ITENSOR_LDLIBS should be set to the list of libraries to link against (possibly -litensor -lpthread -lopenblas).

Linux, GCC, OpenBLAS

Sample configuration for Linux with GCC and OpenBLAS:

export ITENSOR_PATH=...
export CPATH="${ITENSOR_PATH}:${CPATH}"
export LIBRARY_PATH="${ITENSOR_PATH}/lib:${LIBRARY_PATH}"
export ITENSOR_CXX=g++
export ITENSOR_CXXFLAGS='-std=c++17 -DPLATFORM_openblas -fpermissive -DHAVE_LAPACK_CONFIG_H -DLAPACK_COMPLEX_STRUCTURE'
export ITENSOR_LDLIBS='-litensor -lpthread -lopenblas'

macOS, Clang

Sample configuration for macOS with Clang:

export ITENSOR_PATH=...
export CPATH="${ITENSOR_PATH}:${CPATH}"
export LIBRARY_PATH="${ITENSOR_PATH}/lib:${LIBRARY_PATH}"
export ITENSOR_CXX=clang++
export ITENSOR_CXXFLAGS='-std=c++17 -DPLATFORM_macos'
export ITENSOR_LDLIBS='-litensor -framework Accelerate'

Example workflow

Generate sites and Hamiltonian MPO

Full symmetry

1. bin/gen_sites -N 4 --l-max 2 --sites-out workspace/sites
2. • bin/gen_ham -R 1.0 --mpo-cutoff 1e-20 --sites workspace/sites --ham-out workspace/ham
   • bin/gen_ham --anisotropy 0.0 -g -1.0 --sociability 1 --mpo-cutoff 1e-20 --sites workspace/sites --ham-out workspace/ham
   • bin/gen_ham --pbc -R 1.0 --mpo-cutoff 1e-20 --sites workspace/sites --ham-out workspace/ham

Reduced symmetry

1. bin/gen_sites -N 4 --l-max 2 --m-sym 0 --sites-out workspace/sites
2. bin/gen_ham --geom data/geom_tetrahedron -R 1.0 --mpo-cutoff 1e-20 --sites workspace/sites --ham-out workspace/ham

No symmetry

1. bin/gen_sites -N 4 --l-max 2 --lp-sym 0 --sites-out workspace/sites
2. bin/gen_ham --field 0.02 --field-linear -R 1.0 --mpo-cutoff 1e-20 --sites workspace/sites --ham-out workspace/ham

Sweep MPS with DMRG

1. bin/dmrg_sweep --sweep-table data/sample_sweep_table_fast --num-sweeps 5 --sites workspace/sites --ham workspace/ham --mps-out workspace/mps05
2. bin/dmrg_sweep --sweep-table data/sample_sweep_table_fast --mps-cutoff 1e-14 --num-sweeps 5 --first-sweep 6 --sites workspace/sites --ham workspace/ham --mps-in workspace/mps05 --mps-out workspace/mps10
3. bin/dmrg_sweep --sweep-table data/sample_sweep_table_slow --num-sweeps 10 --sites workspace/sites --ham workspace/ham --ortho-mps workspace/mps10 --mps-out workspace/mps_exc

Perform analysis

• bin/analyze --sites workspace/sites --mps workspace/mps10
• bin/sample --num-samples 100 --sites workspace/sites --mps workspace/mps10
• bin/dump_state --sites workspace/sites --mps workspace/mps10

Miscellaneous operations

• bin/embiggen --sites1 workspace/sites --mps1-in workspace/mps10 --sites2 workspace/sites_big --mps2-out workspace/mps10_big

Publications

The following publications contain data created using this package:

• Dmitri Iouchtchenko and Pierre-Nicholas Roy. Ground states of linear rotor chains via the density matrix renormalization group. The Journal of Chemical Physics 148, 134115 (2018). doi:10.1063/1.5024403, arXiv:1805.05420.

References

The sampling algorithm is from Ferris and Vidal (2012) "Perfect sampling with unitary tensor networks" (preprint).

License

Provided under the terms of the MIT license. See LICENSE for more information.