Circular transmon single island qubit

klayout_package/python/kqcircuits/qubits/circular_transmon_single_island.py

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+# This code is part of KQCircuits
+# Copyright (C) 2024 IQM Finland Oy
+#
+# This program is free software: you can redistribute it and/or modify it under the terms of the GNU General Public
+# License as published by the Free Software Foundation, either version 3 of the License, or (at your option) any later
+# version.
+#
+# This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
+# warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along with this program. If not, see
+# https://www.gnu.org/licenses/gpl-3.0.html.
+#
+# The software distribution should follow IQM trademark policy for open-source software
+# (meetiqm.com/developers/osstmpolicy). IQM welcomes contributions to the code. Please see our contribution agreements
+# for individuals (meetiqm.com/developers/clas/individual) and organizations (meetiqm.com/developers/clas/organization).
+
+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
+
+
+@add_parameters_from(Element, n=128)  # n by default is 64, 128 gives a smoother qubit edge
+class CircularTransmonSingleIsland(Qubit):
+    """The PCell declaration for a single island circular transmon.
+
+    A circular transmon consists of one island, connected by a Josephson Junction/s to the ground plane. 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_island = Param(pdt.TypeDouble, "Qubit island radius", 120, unit="μm", docstring="Radius of the qubit island")
+    ground_gap = Param(pdt.TypeDouble, "Ground plane gap width", 80, unit="μm")
+    squid_angle = Param(
+        pdt.TypeDouble,
+        "Angular position of the Josephson Junction/s, where the positive x-axis is 0",
+        120,
+        unit="degrees",
+    )
+
+    # Couplers parameters (the list size define the number of couplers)
+    couplers_r = Param(pdt.TypeDouble, "Radius of the couplers positioning", 150, 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")
+
+    def build(self):
+        # Generate the qubit island (it is the negative shape of the final geometry for visualization)
+        qubit_negative = self._make_qubit_island()
+
+        # 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 qubit 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 for waveguides connections
+        self._add_ports()
+
+    def _make_arc_island(self, island_outer_radius, island_width, swept_angle):
+        # Generate a polygon arc of any size and angle, starting from the outer edge to the inner edge
+        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_outside + points_inside
+        arc_island = pya.DPolygon(points)
+
+        return arc_island
+
+    def _make_qubit_island(self):
+        # Circular qubit island
+        qubit_island = circle_polygon(self.r_island, self.n)
+
+        return pya.Region(qubit_island.to_itype(self.layout.dbu))
+
+    def _add_junction(self, region):
+        # Add the junction to the qubit island
+        squid_origin = arc_points(
+            self.r_island + self.ground_gap, self.squid_angle * math.pi / 180, 2 * math.pi, self.n, pya.DPoint(0, 0)
+        )[0]
+
+        squid_transf = pya.DCplxTrans(1, 90 + self.squid_angle, 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_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_ground_region(self):
+        # Generate the ground region as a filled (negative) circle of the maximum size
+        n_points = self.n
+        return pya.Region(circle_polygon(self.r_island + self.ground_gap, n_points).to_itype(self.layout.dbu))
+
+    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 gap
+        overlapping_margin = 0.5
+        # Outermost coordinate
+        x_end = self.r_island + self.ground_gap
+        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(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(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(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(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_ports(self):
+        # Add couplers ports
+        for i, c_angle in enumerate(map(float, self.couplers_angle)):
+            coupler_origin = arc_points(
+                self.r_island + self.ground_gap, 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(
+            float(self.drive_distance), float(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
+
+    @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))
+        ]