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eef9104 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 | # *******************************************************************************
# Copyright (c) 2026 Ahmad Ali Parr and others.
#
# This program and the accompanying materials are made available under the
# terms of the CPSC Eclipse Strict Copyleft License, Version 1.0, which is
# available in LICENSES/CPSC-ESCL-1.0.txt, or, at your option, under the
# GNU Affero General Public License, Version 3 only, which is available in
# LICENSES/AGPL-3.0.txt. Both options are strict copyleft. There is no
# classpath exception and no permissive relicensing.
#
# SPDX-License-Identifier: LicenseRef-CPSC-ESCL-1.0 OR AGPL-3.0-only
# *******************************************************************************
import numpy as np
import pytest
from cpsc.channel import evolve_in_sector, leakage
from cpsc.hamiltonian import magnetization_of, parity_of, transverse_ising, x4_identity_shift
def test_x4_is_proportional_to_identity():
# The draft quartic does not open a new scattering channel.
assert x4_identity_shift(5, 1.2) == pytest.approx(5 * 1.2 / 24.0)
def test_sector_evolution_has_zero_parity_leakage():
n = 4
initial = 0b0101
psi = evolve_in_sector(n, initial, time=0.7, j=1.0, lam=0.4)
assert leakage(psi, n, parity_of(initial, n)) < 1e-10
assert abs(np.vdot(psi, psi) - 1) < 1e-10
def test_magnetization_projection_refused_when_field_is_on():
with pytest.raises(ValueError):
evolve_in_sector(3, 0b001, time=0.2, lam=0.3, conserve_magnetization=True)
def test_ising_limit_stays_in_weight_sector():
n = 4
initial = 0b0011
psi = evolve_in_sector(
n, initial, time=0.5, j=1.0, lam=0.0, conserve_magnetization=True
)
weight = magnetization_of(initial, n)
for basis, amp in enumerate(psi):
if abs(amp) > 1e-10:
assert magnetization_of(basis, n) == weight
def test_hamiltonian_is_hermitian():
h = transverse_ising(3, j=0.8, lam=0.3)
assert np.allclose(h, h.conj().T)
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