"""
\********************************************************************************
* Copyright (c) 2023 the Qrisp authors
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0.
*
* This Source Code may also be made available under the following Secondary
* Licenses when the conditions for such availability set forth in the Eclipse
* Public License, v. 2.0 are satisfied: GNU General Public License, version 2
* with the GNU Classpath Exception which is
* available at https://www.gnu.org/software/classpath/license.html.
*
* SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
********************************************************************************/
"""
import numpy as np
from scipy.optimize import minimize
from sympy import Symbol
from qrisp import QuantumVariable, h, barrier, rz, rx , cx, QuantumArray, xxyy, p, invert, conjugate, mcp
[docs]
def RX_mixer(qv, beta):
"""
Applies an RX gate to each qubit in ``qv``.
The RX gate is a single-qubit rotation about the x-axis. It is used as a mixer in QAOA to drive transitions between different states.
Parameters
----------
qv : QuantumVariable
The quantum variable to which the RX gate is applied.
beta : float or sympy.Symbol
The phase shift value for the RX gate.
Returns
-------
qv : QuantumVariable
The quantum variable after applying the RX gate.
"""
for i in range(qv.size):
rx(2 * beta, qv[i])
return qv
[docs]
def XY_mixer(qv, beta):
"""
Applies multiple XX+YY gates to ``qv`` such that each qubit has interacted with it's neighbour at least once.
The XX+YY gate is a two-qubit gate that performs rotations around the XY plane. It is used as a mixer in QAOA to drive transitions between different states.
A defining feature of this mixer is the fact, that it keeps the number of ones (or equivalently zeros) in the binary representation of the state invariant.
Parameters
----------
qv : QuantumVariable
The quantum variable to which the XY gate is applied.
beta : float or sympy.Symbol
The phase shift value for the XY gate.
Returns
-------
qv : QuantumVariable
The quantum variable after applying the XY gate.
"""
N = qv.size
for i in range(1, N-2, 2):
xxyy(4*beta, 0, qv[N-2-i], qv[N-1-i])
for i in range(0, N-1, 2):
xxyy(4*beta, 0, qv[N-2-i], qv[N-1-i])
xxyy(4*beta, 0, qv[N-1], qv[0])
return qv
def apply_XY_mixer(quantumcolor_array, beta):
for qcolor in quantumcolor_array:
XY_mixer(qcolor, beta)
return quantumcolor_array
[docs]
def RZ_mixer(qv, beta):
"""
This function applies an RZ gate with a negative phase shift to a given quantum variable.
Parameters
----------
qv : QuantumVariable
The quantum variable to which the RZ gate is applied.
beta : float or sympy.Symbol
The phase shift value for the RZ gate.
"""
rz(-beta, qv)
[docs]
def grover_mixer(qv, beta):
"""
Performs the parametrized Grover diffuser.
Parameters
----------
qv : QuantumVariable
The QuantumVariable to be mixed.
beta : float or sympy.Symbol
The mixing parameter.
"""
from qrisp.grover import diffuser
diffuser(qv, phase = beta)
[docs]
def constrained_mixer_gen(constraint_oracle, winner_state_amount):
r"""
Generates a customized mixer function that leaves arbitrary constraints intact.
The constraints are specified via a ``constraint_oracle`` function, which
is taking a :ref:`QuantumVariable` or :ref:`QuantumArray` and apply a phase $\phi$
(specified by the keyword argument ``phase``) to the states that are allowed
by the constraints.
Additionally the amount of winner states needs to be known. For this the user
needs to provide the function ``winner_state_amount``, that returns the number
of winner states for a given qubit amount. This number can be an approximation,
however faulty values can cause leakage into the state-space that is forbidden
by the constraints.
For more details regarding implementation specifics please check the
corresponding :ref:`tutorial <ConstrainedMixers>`.
Parameters
----------
constraint_oracle : function
A function of a :ref:`QuantumVariable` or :ref:`QuantumArray. Also needs to
support the keyword argument ``phase``. This function should apply the phase
specified by the keyword argument to the allowed states.
winner_state_amount : function
A function of a QuantumVariable or QuantumArray, that returns the amount
of winner states for that QuantumVariable.
Returns
-------
constrained_mixer : function
A mixer function that does not leave the allowed space specified by the oracle.
Examples
--------
We create a mixer function that only mixes among the states where the first and the
last qubit disagree. In more mathematical terms - they satisfy the following
constraint function.
.. math::
f: \mathbb{F}_2^n \rightarrow \mathbb{F}_2, x \rightarrow (x_{n-1} \neq x_0)
::
from qrisp.qaoa import constrained_mixer_gen
from qrisp import QuantumVariable, auto_uncompute, cx, p
@auto_uncompute
def constraint_oracle(qarg, phase):
predicate = QuantumBool()
cx(qarg[0], predicate)
cx(qarg[-1], predicate)
p(phase, predicate)
def winner_state_amount(qarg):
return 2**(len(qarg) - 1)
mixer = constrained_mixer_gen(constraint_oracle, winner_state_amount)
To test the mixer, we create a :ref:`QuantumVariable`:
::
import numpy as np
beta = np.pi
qv = QuantumVariable(3)
qv[:] = "101"
mixer(qv, beta)
print(qv)
#Yields: {'101': 1.0}
#Leaves forbidden states invariant
qv = QuantumVariable(3)
qv[:] = "100"
mixer(qv, beta)
print(qv)
#Yields: {'100': 0.25, '110': 0.25, '001': 0.25, '011': 0.25}
#Only mixes among allowed states
"""
from qrisp.grover import grovers_alg
def prep_psi(qarg):
if isinstance(qarg, QuantumVariable):
qubit_amount = len(qarg)
elif isinstance(qarg, QuantumArray):
qubit_amount = len(qarg.qtype)*len(qarg.flatten())
else:
raise Exception(f"Argument type {type(qarg)} not supported for constrained mixer")
grovers_alg(qarg,
constraint_oracle,
exact = True,
winner_state_amount = winner_state_amount(qarg))
def inv_prep_psi(qarg):
with invert():
prep_psi(qarg)
def constrained_mixer(qarg, beta):
with conjugate(inv_prep_psi)(qarg):
mcp(beta, qarg, ctrl_state = 0)
return constrained_mixer
""" from qrisp import as_hamiltonian
@as_hamiltonian
def mcp_as_hamiltonian(qv, beta):
if qv == "0001":
p(beta, qv)
elif qv == "0011":
p(beta, qv)
elif qv == "0111":
p(beta, qv)
elif qv == "1111":
p(beta, qv) """
#formulate on q_array
def portfolio_mixer():
"""
Multi-Channel constrained mixer to be applied for a discrete portfolio rebalancing problem, as seen in https://arxiv.org/pdf/2006.00354.pdf.
This Mixer keeps the constraints in terms of lots on the portfolio intact. This is achieved by mixing between Dicke States.
Returns:
--------
apply_mixer : function
The Mixer to be applied to a QuantumVariable
Examples:
---------
We initiate a QuantumVariable in the "0011" state and from this partially mix into the Dicke state space with Hamming weight 2.
::
from qrisp import QuantumVariable, x
import numpy as np
qv = QuantumVariable(4)
x(qv[2])
x(qv[3])
from qrisp.qaoa.mixers import portfolio_mixer
mixer_op = portfolio_mixer()
mixer_op(qv, np.pi/8)
"""
from qrisp.misc.dicke_state import dicke_state
def inv_prepare_dicke(qv, k):
with invert():
dicke_state(qv, k)
def apply_mixer(q_array, beta):
half = int(len(q_array[0]))
qv1 = q_array[0]
qv2 = q_array[1]
#omfg this is harcoded-- problematic one
with conjugate(inv_prepare_dicke)(qv1, half):
# mehrere mcp-gates, as hamiltonian
#mcp_as_hamiltonian(qv1, beta=beta)
for i in range(half):
ctrl_state = "0" * (half-i-1) + ("1"*(i+1))
#print(ctrl_state)
mcp(beta, qv1, ctrl_state = ctrl_state)
""" mcp(beta, qv1, ctrl_state = "0001")
mcp(beta, qv1, ctrl_state = "0011")
mcp(beta, qv1, ctrl_state = "0111")
mcp(beta, qv1, ctrl_state = "1111") """
with conjugate(inv_prepare_dicke)(qv2, half):
for i in range(half):
ctrl_state = "0" * (half-i-1) + ("1"*(i+1))
#print(ctrl_state)
mcp(beta, qv2, ctrl_state = ctrl_state)
""" mcp(beta, qv2, ctrl_state = "0001")
mcp(beta, qv2, ctrl_state = "0011")
mcp(beta, qv2, ctrl_state = "0111")
mcp(beta, qv2, ctrl_state = "1111") """
return apply_mixer