Spinless fermionic tight binding: Time evolution yields AssertionError #133
Description
Hi,
Noob here. Tried to time-evolve a TB Hamiltonian for spinless fermions, strting from a half-filled state
import fqe
from openfermion import FermionOperator,hermitian_conjugated
N=2
M=4
half_full = fqe.get_wavefunction(N, N, M)
half_full.set_wfn(strategy='hartree-fock')
half_full.print_wfn()
#Periodic boundary conditions
forward_hop = FermionOperator(((M-1,1),(0,0)))
for i in range(M-1):
forward_hop += FermionOperator(((i,1),(i+1,0)))
tb_hamilt = forward_hop + hermitian_conjugated(forward_hop)
fqe_ham = tb_hamilt
fqe_ham = tb_hamilt
#Evolve ballistically in time for t=10.2
display(fqe_ham)
psi_t = half_full.time_evolve(10.2, fqe_ham)
psi_t.print_wfn()Gave the following traceback:
Sector N = 2 : S_z = 2
a'0011'b'0000' (1+0j)
1.0 [0^ 1] +
1.0 [0^ 3] +
1.0 [1^ 0] +
1.0 [1^ 2] +
1.0 [2^ 1] +
1.0 [2^ 3] +
1.0 [3^ 0] +
1.0 [3^ 2]
---------------------------------------------------------------------------
AssertionError Traceback (most recent call last)
Cell In[6], line 22
20 #Evolve ballistically in time for t=10.2
21 display(fqe_ham)
---> 22 psi_t = half_full.time_evolve(10.2, fqe_ham)
23 psi_t.print_wfn()
File /usr/local/miniforge3/envs/openfermion/lib/python3.10/site-packages/fqe/fqe_decorators.py:393, in wrap_time_evolve.<locals>.convert(self, time, ops, inplace)
383 """ Converts an FermionOperator to hamiltonian.Hamiltonian
384
385 Args:
(...)
388 ops (FermionOperator or Hamiltonian): input operator
389 """
390 hamil = build_hamiltonian(ops,
391 norb=self.norb(),
392 conserve_number=self.conserve_number())
--> 393 return time_evolve(self, time, hamil, inplace)
File /usr/local/miniforge3/envs/openfermion/lib/python3.10/site-packages/fqe/wavefunction.py:1016, in Wavefunction.time_evolve(self, time, hamil, inplace)
1013 else:
1014 transformation = hamil.calc_diag_transform()
-> 1016 permu, low, upp, work_wfn = work_wfn.transform(
1017 transformation)
1019 ci_trans = transformation @ permu
1021 h1e = hamil.transform(ci_trans)
File /usr/local/miniforge3/envs/openfermion/lib/python3.10/site-packages/fqe/wavefunction.py:926, in Wavefunction.transform(self, rotation, low, upp)
924 civec.apply_columns_recursive_inplace(output, output)
925 elif rotation.shape[0] == norb * 2:
--> 926 assert numpy.std(rotation[:norb, norb:]) \
927 + numpy.std(rotation[norb:, :norb]) < 1.0e-8
928 if not external:
929 perm1, low1, upp1 = ludecomp(rotation[:norb, :norb])
AssertionError: Update: Ballistic evolution works fine:
from openfermion import FermionOperator
import fqe
N=3
M=6
N_op = FermionOperator('0^ 0')
for i in range(1, M):
N_op += FermionOperator(((i,1),(i,0)))
wfn_fqe = fqe.get_wavefunction(N, N, M)
wfn_fqe.set_wfn(strategy='hartree-fock')
#N_op+= FermionOperator('0^ 1') + FermionOperator('1^ 0')
psi_t = wfn_fqe.time_evolve(10.2, N_op)
psi_t.print_wfn()Yields
Sector N = 3 : S_z = 3
a'000111'b'000000' (0.6851938352639844+0.7283607678315959j)Uncomment the hopping term, and the AssertionError is raised again.