"""Reference coupling models with time dependence and coupling-owned loss."""
from __future__ import annotations
from typing import Any
from quchip.declarative.dissipation import CollapseChannel
from quchip.declarative.dynamics import CosineCoefficient, TimeDependentTerm
from quchip.declarative.expr import PhysicsExpr
from quchip.declarative.models import CouplingModel
from quchip.declarative.parameters import UNBOUND, Scalar, parameter
[docs]
class ModulatedCapacitive(CouplingModel):
r"""Capacitive interaction with a prescribed sinusoidal strength variation.
The static term is :math:`g_0 n_a^{(q)}n_b^{(q)}` and the modulation is
:math:`\delta g\cos(2\pi\nu_m t+\phi_m)n_a^{(q)}n_b^{(q)}`.
Parameters
----------
device_a, device_b : device or str
Coupled endpoints or their chip labels.
static_strength : float
Static capacitive strength :math:`g_0` in GHz. Can be signed.
modulation_amplitude : float
Modulation amplitude :math:`\delta g` in GHz. Can be signed.
modulation_frequency : float
Modulation frequency :math:`\nu_m` in GHz. Must be positive.
modulation_phase : float, default 0.0
Modulation phase in radians.
label : str or None, default None
Coupling label.
"""
_type_prefix = "modulated_capacitive"
static_strength: Scalar = parameter(default=UNBOUND, unit="GHz", symbol=r"g_0")
modulation_amplitude: Scalar = parameter(default=UNBOUND, unit="GHz", symbol=r"\delta g")
modulation_frequency: Scalar = parameter(
default=UNBOUND,
positive=True,
unit="GHz",
symbol=r"\nu_m",
)
modulation_phase: Scalar = parameter(default=0.0, unit="rad", symbol=r"\phi_m")
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def interaction(self, a: Any, b: Any, p: Any) -> PhysicsExpr:
"""Return the static capacitive interaction.
Parameters
----------
a, b : EndpointOps
Ordered endpoint operator namespaces.
p : ParameterNamespace
Bound coupling parameters.
"""
return p.static_strength * a.charge * b.charge
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def time_terms(self, a: Any, b: Any, p: Any) -> tuple[TimeDependentTerm, ...]:
"""Return the sinusoidally modulated capacitive interaction term.
Parameters
----------
a, b : EndpointOps
Ordered endpoint operator namespaces.
p : ParameterNamespace
Bound coupling parameters.
"""
return (
TimeDependentTerm(
operator=a.charge * b.charge,
coefficient=CosineCoefficient(
amplitude=p.modulation_amplitude,
frequency=p.modulation_frequency,
phase=p.modulation_phase,
),
),
)
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class CollectiveDecayCoupling(CouplingModel):
r"""Exchange coupling with an equal-phase collective decay channel.
Parameters
----------
device_a, device_b : device or str
Coupled endpoints or their chip labels.
exchange_strength : float
Exchange rate :math:`g` in GHz.
decay_rate : float
Non-negative collective Lindblad rate :math:`\gamma_c` in 1/ns.
label : str or None, default None
Coupling label.
Notes
-----
The collapse operator is proportional to ``a + b``, a shared bath channel,
not two independent relaxation channels.
"""
_type_prefix = "collective_decay"
exchange_strength: Scalar = parameter(default=UNBOUND, unit="GHz", symbol="g")
decay_rate: Scalar = parameter(
default=UNBOUND,
nonnegative=True,
unit="1/ns",
symbol=r"\gamma_c",
noise=True,
kw_only=True,
)
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def interaction(self, a: Any, b: Any, p: Any) -> Any:
"""Return the exchange interaction ``g(a b† + a† b)``.
Parameters
----------
a, b : EndpointOps
Ordered endpoint operator namespaces.
p : ParameterNamespace
Bound coupling parameters.
"""
return p.exchange_strength * (a.a * b.adag + a.adag * b.a)
[docs]
def dissipation(self, a: Any, b: Any, p: Any) -> tuple[CollapseChannel, ...]:
"""Return the shared-bath collapse channel proportional to ``a + b``.
Parameters
----------
a, b : EndpointOps
Ordered endpoint operator namespaces.
p : ParameterNamespace
Bound coupling parameters.
"""
return (
CollapseChannel(
a.a * b.I + a.I * b.a,
p.decay_rate,
"collective_decay",
),
)
