Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Add qubit state generation, truncation and expansion. #91

Open
wants to merge 2 commits into
base: master
Choose a base branch
from
Open
Show file tree
Hide file tree
Changes from 1 commit
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Prev Previous commit
improve the qubit_states function
Support a more general way of definition:
- use a list or a string for zero/one/plus/minus state
- use a list of integers for defining arbitrary disentangled quantum states (up to a global phase).
  • Loading branch information
BoxiLi committed Sep 14, 2022
commit 1d3b4aa905c983f34b8e13af5fd77ee704b79fa0
92 changes: 71 additions & 21 deletions src/qutip_qip/qubits.py
Original file line number Diff line number Diff line change
Expand Up @@ -8,36 +8,86 @@
from numpy import sqrt


def qubit_states(N=1, states=[0]):
def qubit_states(states):
"""
Function to define initial state of the qubits.
Shortcut to generate disentangled qubit states.

Parameters
----------
N : Integer
Number of qubits in the register.
states : List
Initial state of each qubit.
states : list or str
- If a list consisting of ``0``, ``1``, ``"0"``, ``"1"``, ``"+"``
and ``"-"``, return the corresponding zero/one/plus/minus state.
- If a string consisting of ``0``, ``1``, ``+``, ``-``,
same as above.
- If a list of float or complex numbers,
each number is mapped to a state of the form
:math:`\\sqrt{1 - |a|^2} \\left|0\\right\\rangle + a |1\\rangle`,
where :math:`a` is the given number.

Returns
-------
qstates : Qobj
List of qubits.
quantum_states : :obj:`qutip.Qobj`
The generated qubit states.

Examples
--------
>>> from qutip_qip.qubits import qubit_states
>>> qubit_states([0, 0]) # doctest: +NORMALIZE_WHITESPACE
Quantum object: dims = [[2, 2], [1, 1]], shape = (4, 1), type = ket
Qobj data =
[[1.]
[0.]
[0.]
[0.]]
>>> qubit_states([1, "+"]) # doctest: +NORMALIZE_WHITESPACE
Quantum object: dims = [[2, 2], [1, 1]], shape =
(4, 1), type = ket
Qobj data =
[[0. ]
[0. ]
[0.70710678]
[0.70710678]]
>>> qubit_states("-") # doctest: +NORMALIZE_WHITESPACE
Quantum object: dims = [[2], [1]], shape = (2, 1), type = ket
Qobj data =
[[ 0.70710678]
[-0.70710678]]
>>> qubit_states("1-") # doctest: +NORMALIZE_WHITESPACE
Quantum object: dims = [[2, 2], [1, 1]], shape =
(4, 1), type = ket
Qobj data =
[[ 0. ]
[ 0. ]
[ 0.70710678]
[-0.70710678]]
>>> import numpy as np
>>> qubit_states([1.j/np.sqrt(2)]) # doctest: +NORMALIZE_WHITESPACE
Quantum object: dims = [[2], [1]], shape = (2, 1), type = ket
Qobj data =
[[0.70710678+0.j ]
[0. +0.70710678j]]
"""
state_list = []
for i in range(N):
if N > len(states) and i >= len(states):
state_list.append(0)
states_map = {
0: qutip.basis(2, 0),
1: qutip.basis(2, 1),
"0": qutip.basis(2, 0),
"1": qutip.basis(2, 1),
"+": (qutip.basis(2, 0) + qutip.basis(2, 1)).unit(),
"-": (qutip.basis(2, 0) - qutip.basis(2, 1)).unit(),
BoxiLi marked this conversation as resolved.
Show resolved Hide resolved
}

states_list = []
for s in states:
if s in states_map:
states_list.append(states_map[s])
elif np.isscalar(s) and abs(s) <= 1:
states_list.append(
s * qutip.basis(2, 1)
+ np.sqrt(1 - abs(s) ** 2) * qutip.basis(2, 0)
)
else:
state_list.append(states[i])

return tensor(
[
alpha * basis(2, 1) + sqrt(1 - alpha**2) * basis(2, 0)
for alpha in state_list
]
)
raise TypeError(f"Invalid input {s}.")
return qutip.tensor(states_list)


def _find_reduced_indices(dims):
Expand Down Expand Up @@ -174,5 +224,5 @@ def expand_qubit_state(state, dims):
output = np.zeros([np.product(d) for d in full_dims], dtype=complex)
reduced_indices1 = reduced_indices if not state.isbra else zero_slice
reduced_indices2 = reduced_indices if not state.isket else zero_slice
output[reduced_indices1[:, np.newaxis], reduced_indices2] = state
output[reduced_indices1[:, np.newaxis], reduced_indices2] = state.full()
return qutip.Qobj(output, dims=full_dims)
8 changes: 4 additions & 4 deletions tests/test_optpulseprocessor.py
Original file line number Diff line number Diff line change
Expand Up @@ -41,8 +41,8 @@ def test_simple_hadamard(self):
qc, num_tslots=num_tslots, evo_time=evo_time, verbose=True)

# test run_state
rho0 = qubit_states(1, [0])
plus = (qubit_states(1, [0]) + qubit_states(1, [1])).unit()
rho0 = qubit_states([0])
plus = (qubit_states([0]) + qubit_states([1])).unit()
result = test.run_state(rho0)
assert_allclose(fidelity(result.states[-1], plus), 1, rtol=1.0e-6)

Expand Down Expand Up @@ -72,8 +72,8 @@ def test_multi_qubits(self):
qc = [tensor([identity(2), cnot()])]
test.load_circuit(qc, num_tslots=num_tslots,
evo_time=evo_time, min_fid_err=1.0e-6)
rho0 = qubit_states(3, [1, 1, 1])
rho1 = qubit_states(3, [1, 1, 0])
rho0 = qubit_states([1, 1, 1])
rho1 = qubit_states([1, 1, 0])
result = test.run_state(
rho0, options=SolverOptions(store_states=True))
assert_(fidelity(result.states[-1], rho1) > 1-1.0e-6)
Expand Down
20 changes: 6 additions & 14 deletions tests/test_processor.py
Original file line number Diff line number Diff line change
Expand Up @@ -276,7 +276,7 @@ def testNoise(self):
Test for Processor with noise
"""
# setup and fidelity without noise
init_state = qubit_states(2, [0, 0, 0, 0])
init_state = qubit_states([0, 0])
tlist = np.array([0., np.pi/2.])
a = destroy(2)
proc = Processor(N=2)
Expand All @@ -285,24 +285,16 @@ def testNoise(self):
proc.set_all_tlist(tlist)
result = proc.run_state(init_state=init_state)
assert_allclose(
fidelity(
result.states[-1],
qubit_states(2, [0, 1, 0, 0])
),
1, rtol=1.e-7
)
fidelity(result.states[-1], qubit_states([0, 1])),
1, rtol=1.e-7)

# decoherence noise
dec_noise = DecoherenceNoise([0.25*a], targets=1)
proc.add_noise(dec_noise)
result = proc.run_state(init_state=init_state)
assert_allclose(
fidelity(
result.states[-1],
qubit_states(2, [0, 1, 0, 0])
),
0.981852, rtol=1.e-3
)
fidelity(result.states[-1], qubit_states([0, 1])),
0.981852, rtol=1.e-3)

# white random noise
proc.model._noise = []
Expand Down Expand Up @@ -342,7 +334,7 @@ def testDrift(self):

def testChooseSolver(self):
# setup and fidelity without noise
init_state = qubit_states(2, [0, 0, 0, 0])
init_state = qubit_states([0, 0])
tlist = np.linspace(0., np.pi/2., 10)
a = destroy(2)
proc = Processor(N=2, t2=100)
Expand Down
41 changes: 18 additions & 23 deletions tests/test_qubits.py
Original file line number Diff line number Diff line change
Expand Up @@ -19,28 +19,26 @@ def testQubitStates(self):
"""
Tests the qubit_states function.
"""
psi0_a = basis(2, 0)
psi0_b = qubit_states()
assert_(psi0_a == psi0_b)

psi1_a = basis(2, 1)
psi1_b = qubit_states(states=[1])
assert_(psi1_a == psi1_b)

psi01_a = tensor(psi0_a, psi1_a)
psi01_b = qubit_states(N=2, states=[0, 1])
assert_(psi01_a == psi01_b)
assert(qubit_states([0]) == basis(2, 0))
assert(qubit_states([1]) == basis(2, 1))
assert(qubit_states([0, 1]) == tensor(basis(2, 0), basis(2, 1)))
plus = (basis(2, 0) + basis(2, 1)).unit()
minus = (basis(2, 0) - basis(2, 1)).unit()
assert(qubit_states("-+") == tensor(minus, plus))
assert(qubit_states("0+") == tensor(basis(2, 0), plus))
assert(qubit_states("+11") == tensor(plus, basis(2, 1), basis(2, 1)))
assert(
qubit_states([1.j/np.sqrt(2), 1.]) ==
tensor(qutip.Qobj([[1/np.sqrt(2)], [1.j/np.sqrt(2)]]), basis(2, 1))
)

@pytest.mark.parametrize(
"state, full_dims",
[
(qutip.rand_dm(18, dims=[[3, 2, 3], [3, 2, 3]]), [3, 2, 3]),
(qutip.rand_ket(18, dims=[[2, 3, 3], [1, 1, 1]]), [2, 3, 3]),
(qutip.rand_dm([3, 2, 3]), [3, 2, 3]),
(qutip.rand_ket([2, 3, 3]), [2, 3, 3]),
(
qutip.Qobj(
qutip.rand_ket(18).full().transpose(),
dims=[[1, 1, 1], [3, 2, 3]],
),
qutip.rand_ket([3, 2, 3]).dag(),
[3, 2, 3],
),
],
Expand Down Expand Up @@ -68,13 +66,10 @@ def test_state_truncation(self, state, full_dims):
@pytest.mark.parametrize(
"state, full_dims",
[
(qutip.rand_dm(8, dims=[[2, 2, 2], [2, 2, 2]]), [3, 2, 3]),
(qutip.rand_ket(8, dims=[[2, 2, 2], [1, 1, 1]]), [2, 3, 3]),
(qutip.rand_dm([2, 2, 2]), [3, 2, 3]),
(qutip.rand_ket([2, 2, 2]), [2, 3, 3]),
(
qutip.Qobj(
qutip.rand_ket(8).full().transpose(),
dims=[[1, 1, 1], [2, 2, 2]],
),
qutip.rand_ket([2, 2, 2]).dag(),
[3, 2, 3],
),
],
Expand Down