from __future__ import annotations
__all__ = ["flux_qubit", "flux_qubit_asymmetric"]
import numpy as np
import gdsfactory as gf
from gdsfactory.component import Component
from gdsfactory.typings import LayerSpec
[docs]
@gf.cell_with_module_name
def flux_qubit(
loop_width: float = 50.0,
loop_height: float = 50.0,
junction_width: float = 0.15,
junction_height: float = 0.3,
alpha_junction_width: float = 0.12,
alpha_junction_height: float = 0.25,
wire_width: float = 2.0,
layer_metal: LayerSpec = (1, 0),
layer_junction: LayerSpec = (2, 0),
layer_alpha_junction: LayerSpec = (3, 0),
port_type: str = "electrical",
) -> Component:
"""Creates a flux qubit (persistent current qubit).
A flux qubit consists of a superconducting loop interrupted by three Josephson junctions.
Two junctions are identical (beta junctions) while the third is smaller (alpha junction)
with roughly 0.5-0.8 times the critical current.
Args:
loop_width: Width of the superconducting loop in μm.
loop_height: Height of the superconducting loop in μm.
junction_width: Width of the beta Josephson junctions in μm.
junction_height: Height of the beta Josephson junctions in μm.
alpha_junction_width: Width of the alpha Josephson junction in μm.
alpha_junction_height: Height of the alpha Josephson junction in μm.
wire_width: Width of the superconducting wires in μm.
layer_metal: Layer for the metal wires.
layer_junction: Layer for the beta Josephson junctions.
layer_alpha_junction: Layer for the alpha Josephson junction.
port_type: Type of port to add to the component.
Returns:
Component: A gdsfactory component with the flux qubit geometry.
"""
c = Component()
# Create the superconducting loop as a hollow rectangle
outer_rect = gf.components.rectangle(
size=(loop_width, loop_height),
layer=layer_metal,
)
inner_rect = gf.components.rectangle(
size=(loop_width - 2 * wire_width, loop_height - 2 * wire_width),
layer=layer_metal,
)
# Create the loop by boolean difference
loop = gf.boolean(
outer_rect,
inner_rect,
operation="not",
layer=layer_metal,
)
# Move loop to be centered at origin (use a temporary component)
loop_centered = Component()
loop_ref = loop_centered.add_ref(loop)
loop_ref.move((-loop_width / 2, -loop_height / 2))
loop_centered.flatten()
# Create gaps for junctions (standalone components, not added to c)
# Bottom gap for alpha junction
alpha_gap = Component()
alpha_gap_rect = alpha_gap.add_ref(
gf.components.rectangle(
size=(alpha_junction_width + 0.1, wire_width + 0.1),
layer=layer_metal,
)
)
alpha_gap_rect.move((-alpha_junction_width / 2 - 0.05, -loop_height / 2 - 0.05))
alpha_gap.flatten()
# Left gap for beta junction
beta_gap_left = Component()
beta_gap_left_rect = beta_gap_left.add_ref(
gf.components.rectangle(
size=(wire_width + 0.1, junction_height + 0.1),
layer=layer_metal,
)
)
beta_gap_left_rect.move((-loop_width / 2 - 0.05, -junction_height / 2 - 0.05))
beta_gap_left.flatten()
# Right gap for beta junction
beta_gap_right = Component()
beta_gap_right_rect = beta_gap_right.add_ref(
gf.components.rectangle(
size=(wire_width + 0.1, junction_height + 0.1),
layer=layer_metal,
)
)
beta_gap_right_rect.move(
(loop_width / 2 - wire_width - 0.05, -junction_height / 2 - 0.05)
)
beta_gap_right.flatten()
# Remove gaps from the loop sequentially
loop_with_gaps = gf.boolean(
loop_centered,
alpha_gap,
operation="not",
layer=layer_metal,
)
loop_with_gaps = gf.boolean(
loop_with_gaps,
beta_gap_left,
operation="not",
layer=layer_metal,
)
loop_with_gaps = gf.boolean(
loop_with_gaps,
beta_gap_right,
operation="not",
layer=layer_metal,
)
c.add_ref(loop_with_gaps)
# Create the alpha junction (smaller)
alpha_junction = gf.components.rectangle(
size=(alpha_junction_width, alpha_junction_height),
layer=layer_alpha_junction,
)
alpha_junction_ref = c.add_ref(alpha_junction)
alpha_junction_ref.move(
(
-alpha_junction_width / 2,
-loop_height / 2 + wire_width / 2 - alpha_junction_height / 2,
)
)
# Create the beta junctions (larger, identical)
beta_junction_left = gf.components.rectangle(
size=(junction_width, junction_height),
layer=layer_junction,
)
beta_junction_left_ref = c.add_ref(beta_junction_left)
beta_junction_left_ref.move(
(-loop_width / 2 + wire_width / 2 - junction_width / 2, -junction_height / 2)
)
beta_junction_right = gf.components.rectangle(
size=(junction_width, junction_height),
layer=layer_junction,
)
beta_junction_right_ref = c.add_ref(beta_junction_right)
beta_junction_right_ref.move(
(loop_width / 2 - wire_width / 2 - junction_width / 2, -junction_height / 2)
)
# Add control lines for flux bias
control_line_left = gf.components.rectangle(
size=(20.0, 2.0),
layer=layer_metal,
)
control_line_left_ref = c.add_ref(control_line_left)
control_line_left_ref.move((-loop_width / 2 - 30.0, -1.0))
control_line_right = gf.components.rectangle(
size=(20.0, 2.0),
layer=layer_metal,
)
control_line_right_ref = c.add_ref(control_line_right)
control_line_right_ref.move((loop_width / 2 + 10.0, -1.0))
c.flatten()
# Add ports for flux control
c.add_port(
name="flux_control_left",
center=(-loop_width / 2 - 40.0, 0),
width=2.0,
orientation=180,
layer=layer_metal,
port_type=port_type,
)
c.add_port(
name="flux_control_right",
center=(loop_width / 2 + 40.0, 0),
width=2.0,
orientation=0,
layer=layer_metal,
port_type=port_type,
)
# Add readout connection
c.add_port(
name="readout",
center=(0, loop_height / 2 + 10.0),
width=wire_width,
orientation=90,
layer=layer_metal,
port_type=port_type,
)
# Add metadata
c.info["qubit_type"] = "flux_qubit"
c.info["loop_width"] = loop_width
c.info["loop_height"] = loop_height
c.info["beta_junction_area"] = junction_width * junction_height
c.info["alpha_junction_area"] = alpha_junction_width * alpha_junction_height
c.info["alpha_beta_ratio"] = (alpha_junction_width * alpha_junction_height) / (
junction_width * junction_height
)
return c
[docs]
@gf.cell_with_module_name
def flux_qubit_asymmetric(
loop_width: float = 60.0,
loop_height: float = 40.0,
junction_width: float = 0.15,
junction_height: float = 0.3,
alpha_junction_width: float = 0.12,
alpha_junction_height: float = 0.25,
wire_width: float = 2.0,
asymmetry_angle: float = 15.0,
layer_metal: LayerSpec = (1, 0),
layer_junction: LayerSpec = (2, 0),
layer_alpha_junction: LayerSpec = (3, 0),
port_type: str = "electrical",
) -> Component:
"""Creates an asymmetric flux qubit for reduced flux noise sensitivity.
An asymmetric flux qubit has a loop geometry that is not perfectly symmetric,
which can help reduce sensitivity to flux noise while maintaining controllability.
Args:
loop_width: Width of the superconducting loop in μm.
loop_height: Height of the superconducting loop in μm.
junction_width: Width of the beta Josephson junctions in μm.
junction_height: Height of the beta Josephson junctions in μm.
alpha_junction_width: Width of the alpha Josephson junction in μm.
alpha_junction_height: Height of the alpha Josephson junction in μm.
wire_width: Width of the superconducting wires in μm.
asymmetry_angle: Angle of asymmetry in degrees.
layer_metal: Layer for the metal wires.
layer_junction: Layer for the beta Josephson junctions.
layer_alpha_junction: Layer for the alpha Josephson junction.
port_type: Type of port to add to the component.
Returns:
Component: A gdsfactory component with the asymmetric flux qubit geometry.
"""
c = Component()
angle_rad = np.radians(asymmetry_angle)
x_offset = loop_height * np.tan(angle_rad)
# Create asymmetric loop as outer/inner polygon boolean
# The right side is tilted by asymmetry_angle
outer_points = [
(-loop_width / 2, -loop_height / 2),
(loop_width / 2, -loop_height / 2),
(loop_width / 2 + x_offset, loop_height / 2),
(-loop_width / 2, loop_height / 2),
]
inner_points = [
(-loop_width / 2 + wire_width, -loop_height / 2 + wire_width),
(loop_width / 2 - wire_width, -loop_height / 2 + wire_width),
(loop_width / 2 - wire_width + x_offset, loop_height / 2 - wire_width),
(-loop_width / 2 + wire_width, loop_height / 2 - wire_width),
]
outer_comp = Component()
outer_comp.add_polygon(outer_points, layer=layer_metal)
inner_comp = Component()
inner_comp.add_polygon(inner_points, layer=layer_metal)
loop = gf.boolean(outer_comp, inner_comp, operation="not", layer=layer_metal)
c.add_ref(loop)
# Create the alpha junction (smaller, at bottom)
alpha_junction = gf.components.rectangle(
size=(alpha_junction_width, alpha_junction_height),
layer=layer_alpha_junction,
)
alpha_junction_ref = c.add_ref(alpha_junction)
alpha_junction_ref.move(
(
-alpha_junction_width / 2,
-loop_height / 2 + wire_width / 2 - alpha_junction_height / 2,
)
)
# Create the beta junctions (larger, identical, at sides)
beta_junction_left = gf.components.rectangle(
size=(junction_width, junction_height),
layer=layer_junction,
)
beta_junction_left_ref = c.add_ref(beta_junction_left)
beta_junction_left_ref.move(
(-loop_width / 2 + wire_width / 2 - junction_width / 2, -junction_height / 2)
)
# Right side center x is shifted by half the x_offset
right_center_x = loop_width / 2 - wire_width / 2 + x_offset / 2
beta_junction_right = gf.components.rectangle(
size=(junction_width, junction_height),
layer=layer_junction,
)
beta_junction_right_ref = c.add_ref(beta_junction_right)
beta_junction_right_ref.move(
(right_center_x - junction_width / 2, -junction_height / 2)
)
# Add control and readout ports
c.add_port(
name="flux_control",
center=(0, loop_height / 2 + 10.0),
width=wire_width,
orientation=90,
layer=layer_metal,
port_type=port_type,
)
c.add_port(
name="readout",
center=(loop_width / 2 + x_offset + 10.0, 0),
width=wire_width,
orientation=0,
layer=layer_metal,
port_type=port_type,
)
# Add metadata
c.info["qubit_type"] = "flux_qubit_asymmetric"
c.info["loop_width"] = loop_width
c.info["loop_height"] = loop_height
c.info["asymmetry_angle"] = asymmetry_angle
c.info["beta_junction_area"] = junction_width * junction_height
c.info["alpha_junction_area"] = alpha_junction_width * alpha_junction_height
c.info["alpha_beta_ratio"] = (alpha_junction_width * alpha_junction_height) / (
junction_width * junction_height
)
c.flatten()
return c
