# This code is part of KQCircuits
# Copyright (C) 2023 IQM Finland Oy
#
# This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
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# version.
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import math
from kqcircuits.elements.element import Element
from kqcircuits.pya_resolver import pya
from kqcircuits.qubits.qubit import Qubit
from kqcircuits.util.geometry_helper import circle_polygon, arc_points
from kqcircuits.util.parameters import Param, pdt, add_parameters_from
from kqcircuits.util.refpoints import WaveguideToSimPort, JunctionSimPort
[docs]
@add_parameters_from(Element, n=180)
class ConcentricTransmon(Qubit):
"""The PCell declaration for a concentric transmon.
A concentric transmon consists of two islands, one inner and one outer, connected by a Josephson Junction/s.
Multiple couplers can be defined. They can have custom waveguide impedance, size and shape.
Each coupler has reference points, numbered starting from 1. Driveline can be connected to the drive port.
"""
# Qubit geometry
r_inner = Param(
pdt.TypeDouble,
"Internal island radius",
120,
unit="μm",
docstring="Radius of the outer edge of the inner island",
)
r_outer = Param(
pdt.TypeDouble,
"External island radius, measured at the outer edge",
250,
unit="μm",
docstring="Radius of the external qubit island",
)
outer_island_width = Param(
pdt.TypeDouble, "Outer island radial width", 80, unit="μm", docstring="Width of the external island"
)
ground_gap = Param(pdt.TypeDouble, "Ground plane padding", 80, unit="μm")
squid_angle = Param(
pdt.TypeDouble, "Angular position of the Josephson Junction/s, where the positive x-axis", 120, unit="degrees"
)
# Couplers parameters (the list size define the number of couplers)
couplers_r = Param(pdt.TypeDouble, "Radius of the couplers positioning", 290, unit="[μm]")
couplers_a = Param(pdt.TypeList, "Width of the coupler waveguide's center conductors", [10, 3, 4.5], unit="[μm]")
couplers_b = Param(pdt.TypeList, "Width of the coupler waveguide's gaps", [6, 32, 20], unit="[μm]")
couplers_angle = Param(
pdt.TypeList,
"Positioning angles of the couplers, where 0deg corresponds to positive x-axis",
[340, 60, 210],
unit="[degrees]",
)
couplers_width = Param(pdt.TypeList, "Radial widths of the arc couplers", [10, 20, 30], unit="[μm]")
couplers_arc_amplitude = Param(pdt.TypeList, "Couplers angular extension", [35, 45, 15], unit="[degrees]")
# Drive port parameters
drive_angle = Param(
pdt.TypeDouble, "Angle of the drive port, where 0deg corresponds to positive x-axis", 300, unit="degrees"
)
drive_distance = Param(pdt.TypeDouble, "Distance of the driveline, measured from qubit centre", 400, unit="µm")
[docs]
def build(self):
self.x_end = self.r_outer + self.ground_gap # Define the outermost qubit coordinate
# Generate the qubit islands (they are the negative shape of the final geometry)
qubit_negative = self._make_qubit_islands()
# Generate the coupler islands
coupler_islands_region = self._make_coupler_island()
# Add the waveguides connecting the couplers to external waveguides
waveguide, waveguide_gap = self._make_waveguides()
# Add the Josephson Junction/s
self._add_junction(qubit_negative)
# Define the capacitor in the ground (final polarity)
ground_region = self._make_ground_region()
qubit = (
ground_region - qubit_negative + waveguide_gap - coupler_islands_region - waveguide
) # Operations order is important!
self.cell.shapes(self.get_layer("base_metal_gap_wo_grid")).insert(qubit)
# Protection region from the ground grid
region_protection = self._get_protection_region(ground_region)
self.add_protection(region_protection)
# Couplers and driveline ports
self._add_ports()
def _make_arc_island(self, island_outer_radius, island_width, swept_angle):
# Generate a polygon arc of any size and angle
angle_rad = math.radians(swept_angle)
points_outside = arc_points(island_outer_radius, -angle_rad / 2, angle_rad / 2, self.n)
points_inside = arc_points(island_outer_radius - island_width, angle_rad / 2, -angle_rad / 2, self.n)
points = points_inside + points_outside
arc_island = pya.DPolygon(points)
return arc_island
def _make_qubit_islands(self):
# Generate a region of the qubit shunting capacitor
capacitor_islands = []
# Inner circular island
inner_island = circle_polygon(self.r_inner, self.n)
capacitor_islands.append(inner_island)
# Outer cylindrical island
outer_island = self._make_arc_island(self.r_outer, self.outer_island_width, 360)
capacitor_islands.append(outer_island)
return pya.Region([poly.to_itype(self.layout.dbu) for poly in capacitor_islands])
def _make_coupler_island(self):
# Generate the regions of the coupler islands.
round_corner = 5
coupler_islands_region = pya.Region()
# Generate all the couplers in the same region
for c_angle, c_width, c_arc_ampl in zip(self.couplers_angle, self.couplers_width, self.couplers_arc_amplitude):
coupler_island = self._make_arc_island(
self.couplers_r + float(c_width) / 2, float(c_width), float(c_arc_ampl)
)
coupler_island_region = (
pya.Region(coupler_island.to_itype(self.layout.dbu))
.round_corners(round_corner / self.layout.dbu, round_corner / self.layout.dbu, self.n)
.transformed(pya.ICplxTrans(1, float(c_angle), False, 0, 0))
)
coupler_islands_region += coupler_island_region
return coupler_islands_region
def _make_waveguides(self):
# Make the waveguides for each coupler with custom impedance and return the region
waveguides_signal_region = pya.Region()
waveguides_gap_region = pya.Region()
# Add the waveguides inside the ground padding
overlapping_margin = 0.5
for c_a, c_b, c_angle in zip(self.couplers_a, self.couplers_b, self.couplers_angle):
waveguide_signal = pya.Region(
pya.DPolygon(
[
pya.DPoint(self.x_end + overlapping_margin, float(c_a) / 2),
pya.DPoint(self.couplers_r, float(c_a) / 2),
pya.DPoint(self.couplers_r, -float(c_a) / 2),
pya.DPoint(self.x_end + overlapping_margin, -float(c_a) / 2),
]
).to_itype(self.layout.dbu)
).transformed(pya.ICplxTrans(1, float(c_angle), False, 0, 0))
waveguide_gap = pya.Region(
pya.DPolygon(
[
pya.DPoint(self.x_end, float(c_a) / 2 + float(c_b)),
pya.DPoint(self.couplers_r, float(c_a) / 2 + float(c_b)),
pya.DPoint(self.couplers_r, -float(c_a) / 2 - float(c_b)),
pya.DPoint(self.x_end, -float(c_a) / 2 - float(c_b)),
]
).to_itype(self.layout.dbu)
).transformed(pya.ICplxTrans(1, float(c_angle), False, 0, 0))
waveguides_signal_region += waveguide_signal
waveguides_gap_region += waveguide_gap
return waveguides_signal_region, waveguides_gap_region
def _add_junction(self, region):
# Add the junction to the qubit islands
squid_origin = arc_points(
self.r_outer - self.outer_island_width,
self.squid_angle * math.pi / 180,
2 * math.pi,
self.n,
pya.DPoint(0, 0),
)[0]
squid_transf = pya.DCplxTrans(1, self.squid_angle + 90, False, squid_origin)
self.produce_squid(squid_transf)
squid_distance_from_centre = self.refpoints["squid_port_common"].distance(self.refpoints["base"])
# Connect the junction to the inner island
squid_connection = pya.Region(
squid_transf
* pya.DPolygon(
[
pya.DPoint(-4, 0),
pya.DPoint(-4, -squid_distance_from_centre - 0.5),
pya.DPoint(4, -squid_distance_from_centre - 0.5),
pya.DPoint(4, 0),
]
).to_itype(self.layout.dbu)
)
region += squid_connection
def _make_ground_region(self):
# Generate the ground region as a filled circle of the maximum size
return pya.Region(circle_polygon(self.x_end, self.n).to_itype(self.layout.dbu))
def _add_ports(self):
# Add couplers ports
for i, c_angle in enumerate(map(float, self.couplers_angle)):
coupler_origin = arc_points(self.x_end, c_angle * math.pi / 180, 2 * math.pi, self.n, pya.DPoint(0, 0))[0]
coupler_transf = pya.DCplxTrans(1, 90 + c_angle, False, coupler_origin)
self.add_port(
f"coupler_{i + 1}",
coupler_transf * pya.DPoint(0, 0),
direction=pya.DVector(coupler_transf * pya.DPoint(0, 0)),
)
# Add driveline port
drive_origin = arc_points(
self.drive_distance, self.drive_angle * math.pi / 180, 2 * math.pi, self.n, pya.DPoint(0, 0)
)[0]
drive_transf = pya.DCplxTrans(1, 90 + self.drive_angle, False, drive_origin)
self.add_port("drive", drive_transf * pya.DPoint(0, 0), direction=pya.DVector(drive_transf * pya.DPoint(0, 0)))
def _get_protection_region(self, region):
# Region which we don't want to cover with the automatically generated ground grid
protection_region = region.sized(self.margin / self.layout.dbu, self.margin / self.layout.dbu, 2)
return protection_region
[docs]
@classmethod
def get_sim_ports(cls, simulation):
ports = [JunctionSimPort()]
return ports + [
WaveguideToSimPort(
f"port_coupler_{i+1}", side="bottom", a=simulation.couplers_a[i], b=simulation.couplers_b[i]
)
for i in range(len(simulation.couplers_angle))
]