"""Reference device models, including device-owned time dependence and 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.ops import LocalOps
from quchip.declarative.parameters import UNBOUND, Scalar, parameter
from quchip.devices.fock import FockDevice
from quchip.devices.kerr_cavity import KerrCavity
[docs]
class FrequencyModulatedMode(FockDevice):
r"""Harmonic mode with a prescribed sinusoidal frequency variation.
The authored Hamiltonian is :math:`H_0=\omega_0 n` and the time term is
:math:`\delta\omega\cos(2\pi\nu_m t+\phi_m)n`. Frequencies are ordinary GHz
and ``t`` is in ns.
Parameters
----------
frequency : float
Bare mode frequency :math:`\omega_0` in GHz. Must be positive.
modulation_amplitude : float
Frequency excursion :math:`\delta\omega` in GHz. Can be signed.
modulation_frequency : float
Modulation frequency :math:`\nu_m` in GHz. Must be positive.
modulation_phase : float, default 0.0
Phase :math:`\phi_m` in radians.
levels : int, default 10
Fock truncation dimension.
label : str or None, default None
Device label. ``None`` selects an automatic label.
T1 : float or None, default None
Energy-relaxation time in ns. ``None`` disables T1 relaxation.
T2 : float or None, default None
Total 0-1 coherence time in ns. If both are set, ``T2 <= 2*T1``.
thermal_occupation : float or None, default None
Dimensionless mean bath occupation. ``None`` disables absorption.
References
----------
See Didier et al., *Phys. Rev. A* 97, 022330 (2018),
https://doi.org/10.1103/PhysRevA.97.022330, for parametrically modulated
transmon models.
"""
_type_prefix = "frequency_modulated_mode"
_default_levels = 10
approximation = (
"Single harmonic mode in a fixed Fock basis with an externally prescribed "
"sinusoidal frequency coefficient."
)
frequency: Scalar = parameter(default=UNBOUND, positive=True, unit="GHz", symbol=r"\omega_0")
modulation_amplitude: Scalar = parameter(default=UNBOUND, unit="GHz", symbol=r"\delta\omega")
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")
@property
def freq(self) -> Any:
"""Bare reference frequency in GHz."""
return self.frequency
[docs]
def local_hamiltonian(self, op: LocalOps, p: Any) -> PhysicsExpr:
"""Return the static harmonic Hamiltonian.
Parameters
----------
op : LocalOps
Local operator namespace.
p : ParameterNamespace
Bound symbolic parameters.
"""
return p.frequency * op.n
[docs]
def time_terms(self, op: LocalOps, p: Any) -> tuple[TimeDependentTerm, ...]:
"""Return the sinusoidal frequency-modulation term.
Parameters
----------
op : LocalOps
Local operator namespace.
p : ParameterNamespace
Bound symbolic parameters.
"""
return (
TimeDependentTerm(
operator=op.n,
coefficient=CosineCoefficient(
amplitude=p.modulation_amplitude,
frequency=p.modulation_frequency,
phase=p.modulation_phase,
),
),
)
[docs]
class LossyKerrCavity(KerrCavity):
r"""Kerr cavity with an intrinsic two-photon-loss channel.
Parameters
----------
two_photon_loss_rate : float
Non-negative two-photon Lindblad rate :math:`\kappa_2` in 1/ns.
freq, kerr, levels, label, T1, T2, thermal_occupation
Inherited :class:`~quchip.devices.kerr_cavity.KerrCavity` parameters.
"""
_type_prefix = "lossy_kerr_cavity"
two_photon_loss_rate: Scalar = parameter(
default=UNBOUND,
nonnegative=True,
unit="1/ns",
symbol=r"\kappa_2",
noise=True,
kw_only=True,
)
[docs]
def dissipation(self, op: Any, p: Any) -> tuple[CollapseChannel, ...]:
"""Return inherited channels plus two-photon loss at ``kappa_2``.
Parameters
----------
op : LocalOps
Local operator namespace.
p : ParameterNamespace
Bound symbolic parameters.
"""
return super().dissipation(op, p) + (
CollapseChannel(op.a @ op.a, p.two_photon_loss_rate, "two_photon_loss"),
)
