Add microwave-to-optical quantum transducer components and models

docs/bibliography.bib

@@ -89,6 +89,19 @@ @book{clarkeSQUIDHandbook2004
   langid = {english},
   lccn = {537.5}
 }
+@article{delaneyNondestructiveOpticalReadout2022,
+  title = {Non-Destructive Optical Readout of a Superconducting Qubit},
+  author = {Delaney, R. D. and Urmey, M. D. and Mittal, S. and Brubaker, B. M. and Kindem, J. M. and Burns, P. S. and Regal, C. A. and Lehnert, K. W.},
+  year = {2022},
+  month = mar,
+  journal = {Nature},
+  volume = {606},
+  number = {7912},
+  pages = {489--493},
+  issn = {0028-0836, 1476-4687},
+  doi = {10.1038/s41586-022-04720-2},
+  langid = {english}
+}
 @article{dudaParameterOptimizationUnimon2025,
   title = {Parameter Optimization for the Unimon Qubit},
   author = {Duda, Rostislav and Hyypp\"{a}, Eric and Mukkula, Olli and Vadimov, Vasilii and M\"{o}tt\"{o}nen, Mikko},
@@ -288,6 +301,32 @@ @article{krantzQuantumEngineersGuide2019
   doi = {10.1063/1.5089550},
   langid = {english}
 }
+@article{lauksTransducerCoupling2020,
+  title = {Perspectives on Quantum Transduction},
+  author = {Lauk, Nikolai and Sinclair, Neil and Barzanjeh, Shabir and Covey, Jacob P. and Saffman, Mark and Spiropulu, Maria and Simon, Christoph},
+  year = {2020},
+  month = jan,
+  journal = {Quantum Science and Technology},
+  volume = {5},
+  number = {2},
+  pages = {020501},
+  issn = {2058-9565},
+  doi = {10.1088/2058-9565/ab788a},
+  langid = {english}
+}
+@article{lecocqControlReadoutSuperconducting2021,
+  title = {Control and Readout of a Superconducting Qubit Using a Photonic Link},
+  author = {Lecocq, F. and Quinlan, F. and Cicak, K. and Aumentado, J. and Diddams, S. A. and Teufel, J. D.},
+  year = {2021},
+  month = mar,
+  journal = {Nature},
+  volume = {591},
+  number = {7851},
+  pages = {575--579},
+  issn = {0028-0836, 1476-4687},
+  doi = {10.1038/s41586-021-03268-x},
+  langid = {english}
+}
 @article{leizhuAccurateCircuitModel2000,
   title = {Accurate Circuit Model of Interdigital Capacitor and Its Application to Design of New Quasi-Lumped Miniaturized Filters with Suppression of Harmonic Resonance},
   author = {{Lei Zhu} and Wu, Ke},
@@ -359,6 +398,19 @@ @article{McCumber1968
   month = jun,
   pages = {3113–3118}
 }
+@article{mirhosseiniQuantumTransductionOptical2020,
+  title = {Quantum Transduction of Optical Photons from a Superconducting Qubit},
+  author = {Mirhosseini, Mohammad and Sipahigil, Alp and Kalaee, Mahmoud and Painter, Oskar},
+  year = {2020},
+  month = aug,
+  journal = {Nature},
+  volume = {588},
+  number = {7839},
+  pages = {599--603},
+  issn = {0028-0836, 1476-4687},
+  doi = {10.1038/s41586-020-3038-6},
+  langid = {english}
+}
 @article{motzoi2009DRAGpulse,
   title = {Simple Pulses for Elimination of Leakage in Weakly Nonlinear Qubits},
   author = {Motzoi, F. and Gambetta, J. M. and Rebentrost, P. and Wilhelm, F. K.},
@@ -509,6 +561,13 @@ @article{tuokkolaMethodsAchieveNearmillisecond2025
   doi = {10.1038/s41467-025-61126-0},
   langid = {english}
 }
+@unpublished{warnerCoherentControlSuperconducting2023,
+  title = {Coherent Control of a Superconducting Qubit Using Light},
+  author = {Warner, Hana K. and Holzgrafe, Jeffrey and Yankelevich, Beatriz and Barton, David and Poletto, Stefano and Xin, C. J. and Sinclair, Neil and Zhu, Di and Sete, Eyob and Langley, Brandon and Batson, Emma and Colangelo, Marco and Shams-Ansari, Amirhassan and Joe, Graham and Berggren, Karl K. and Jiang, Liang and Reagor, Matthew and Lon{\v c}ar, Marko},
+  year = {2023},
+  month = dec,
+  doi = {10.48550/arXiv.2310.16155}
+}
 @article{yostSolidstateQubitsIntegrated2020,
   title = {Solid-State Qubits Integrated with Superconducting through-Silicon Vias},
   author = {Yost, D. R. W. and Schwartz, M. E. and Mallek, J. and Rosenberg, D. and Stull, C. and Yoder, J. L. and Calusine, G. and Cook, M. and Das, R. and Day, A. L. and Golden, E. B. and Kim, D. K. and Melville, A. and Niedzielski, B. M. and Woods, W. and Kerman, A. J. and Oliver, W. D.},

qpdk/cells/__init__.py

@@ -12,6 +12,7 @@
 from qpdk.cells.launcher import *
 from qpdk.cells.resonator import *
 from qpdk.cells.snspd import *
+from qpdk.cells.transducer import *
 from qpdk.cells.transmon import *
 from qpdk.cells.tsv import *
 from qpdk.cells.unimon import *

qpdk/cells/transducer.py

@@ -0,0 +1,302 @@
+r"""Microwave-to-optical quantum transducer layout components.
+
+This module provides layout components for the microwave side of
+superconducting-to-optical quantum transducers.  Two dominant physical
+mechanisms for microwave-to-optical transduction exist in the literature:
+
+1. **Cavity electro-optic (CEO) transduction** – a microwave LC resonator
+   is capacitively coupled to optical modes in a material with a
+   :math:`\chi^{(2)}` nonlinearity (e.g. thin-film lithium niobate).  See
+   :cite:`warnerCoherentControlSuperconducting2023,lauksTransducerCoupling2020`.
+
+2. **Piezo-optomechanical transduction** – a superconducting qubit or
+   microwave resonator is piezoelectrically coupled to a mechanical mode,
+   which is in turn optomechanically coupled to an optical cavity.  See
+   :cite:`mirhosseiniQuantumTransductionOptical2020,delaneyNondestructiveOpticalReadout2022`.
+
+The layout components in this module represent the **microwave side** of
+these hybrid transducer systems – i.e. the structures that would be
+fabricated on a superconducting chip and subsequently integrated with an
+optical or piezoelectric chip via flip-chip bonding, wire bonding, or
+coaxial cable.
+
+References:
+    - :cite:`mirhosseiniQuantumTransductionOptical2020`
+    - :cite:`warnerCoherentControlSuperconducting2023`
+    - :cite:`delaneyNondestructiveOpticalReadout2022`
+    - :cite:`lauksTransducerCoupling2020`
+"""
+
+from __future__ import annotations
+
+import gdsfactory as gf
+from gdsfactory.component import Component
+from gdsfactory.typings import CrossSectionSpec, LayerSpec
+
+from qpdk.cells.capacitor import plate_capacitor
+from qpdk.cells.inductor import meander_inductor
+from qpdk.cells.waveguides import straight
+from qpdk.helper import show_components
+from qpdk.tech import LAYER
+
+
+@gf.cell
+def electro_optic_transducer(
+    inductor_n_turns: int = 8,
+    inductor_turn_length: float = 200.0,
+    capacitor_length: float = 100.0,
+    capacitor_width: float = 100.0,
+    capacitor_gap: float = 5.0,
+    coupling_pad_size: tuple[float, float] = (200.0, 100.0),
+    coupling_pad_gap: float = 20.0,
+    feedline_length: float = 100.0,
+    cross_section: CrossSectionSpec = "cpw",
+    layer_metal: LayerSpec = LAYER.M1_DRAW,
+    layer_eo_coupler: LayerSpec = LAYER.IND,
+) -> Component:
+    r"""Microwave LC resonator for cavity electro-optic transduction.
+
+    Creates the microwave side of a cavity electro-optic
+    microwave-to-optical quantum transducer (CEO-MOQT).  The layout
+    consists of:
+
+    * A lumped-element LC resonator (meander inductor in parallel with a
+      plate capacitor) whose resonance frequency matches the target
+      microwave transition, typically :math:`\omega_m / 2\pi \sim 5\text{--}8\;\text{GHz}`.
+    * A coupling capacitor pad pair placed adjacent to the LC resonator.
+      This pad is intended for capacitive coupling to a photonic chip
+      carrying optical ring resonators in thin-film lithium niobate (TFLN).
+    * CPW feedline connections for external microwave drive and readout.
+
+    The transduction process relies on the :math:`\chi^{(2)}`
+    nonlinearity of TFLN to mediate energy exchange between the
+    microwave LC mode and two hybridised optical modes separated by the
+    microwave frequency :math:`\omega_m`.
+
+    .. svgbob::
+
+            CPW feedline
+          o1 ──────────┐
+                       │  "coupling cap pads"
+                   ┌───┤───┐
+                   │   │   │ ← to optical chip (TFLN)
+                   └───┤───┘
+                       │
+                 ┌─────┤─────┐
+                 │  meander   │
+                 │  inductor  │
+                 │     ║      │
+                 │  plate cap │
+                 └─────┤─────┘
+                       │
+          o2 ──────────┘
+            CPW feedline
+
+    See :cite:`warnerCoherentControlSuperconducting2023` for experimental
+    details and :cite:`lauksTransducerCoupling2020` for theory.
+
+    Args:
+        inductor_n_turns: Number of meander turns for the inductor.
+        inductor_turn_length: Length of each meander turn in µm.
+        capacitor_length: Length of the plate capacitor pads in µm.
+        capacitor_width: Width of the plate capacitor pads in µm.
+        capacitor_gap: Gap between the plate capacitor pads in µm.
+        coupling_pad_size: (width, height) of each EO coupling pad in µm.
+        coupling_pad_gap: Gap between the two EO coupling pads in µm.
+        feedline_length: Length of CPW feedline sections in µm.
+        cross_section: Cross-section specification for CPW feedlines.
+        layer_metal: Metal layer for all superconducting structures.
+        layer_eo_coupler: Layer for the electro-optic coupling pads
+            (typically the indium bump layer for flip-chip integration).
+
+    Returns:
+        Component with ports ``o1`` and ``o2`` (CPW feedline) and
+        ``eo_coupler`` (placement port at the EO coupling pad centre).
+    """
+    c = Component()
+
+    # --- Plate capacitor forms the main resonator capacitance ---
+    cap = c.add_ref(
+        plate_capacitor(
+            length=capacitor_length, width=capacitor_width, gap=capacitor_gap
+        )
+    )
+
+    # --- Meander inductor in parallel with capacitor ---
+    ind = c.add_ref(
+        meander_inductor(n_turns=inductor_n_turns, turn_length=inductor_turn_length)
+    )
+    # Position inductor above the capacitor
+    ind.dmove((
+        cap.dcenter[0] - ind.dcenter[0],
+        cap.dbbox().top + 20 - ind.dcenter[1],
+    ))
+
+    # --- EO coupling pads for flip-chip integration ---
+    pad_w, pad_h = coupling_pad_size
+    # Left pad
+    left_pad = c.add_ref(
+        gf.components.rectangle(size=(pad_w, pad_h), layer=layer_eo_coupler)
+    )
+    left_pad.dmove((
+        -pad_w - coupling_pad_gap / 2,
+        ind.dbbox().top + 20,
+    ))
+    # Right pad
+    right_pad = c.add_ref(
+        gf.components.rectangle(size=(pad_w, pad_h), layer=layer_eo_coupler)
+    )
+    right_pad.dmove((
+        coupling_pad_gap / 2,
+        ind.dbbox().top + 20,
+    ))
+
+    # --- CPW feedlines connected to capacitor ports ---
+    feed_left = c.add_ref(straight(length=feedline_length, cross_section=cross_section))
+    feed_left.connect("o2", cap.ports["o1"])
+
+    feed_right = c.add_ref(
+        straight(length=feedline_length, cross_section=cross_section)
+    )
+    feed_right.connect("o2", cap.ports["o2"])
+
+    # --- Ports ---
+    c.add_port(name="o1", port=feed_left.ports["o1"])
+    c.add_port(name="o2", port=feed_right.ports["o1"])
+
+    # Placement port at EO coupler centre
+    eo_center_x = (left_pad.dcenter[0] + right_pad.dcenter[0]) / 2
+    eo_center_y = (left_pad.dcenter[1] + right_pad.dcenter[1]) / 2
+    c.add_port(
+        name="eo_coupler",
+        center=(eo_center_x, eo_center_y),
+        width=pad_w * 2 + coupling_pad_gap,
+        orientation=90,
+        layer=layer_eo_coupler,
+        port_type="placement",
+    )
+
+    # --- Metadata ---
+    c.info["inductor_n_turns"] = inductor_n_turns
+    c.info["inductor_turn_length"] = inductor_turn_length
+    c.info["capacitor_length"] = capacitor_length
+    c.info["capacitor_width"] = capacitor_width
+    c.info["capacitor_gap"] = capacitor_gap
+    c.info["transducer_type"] = "electro_optic"
+
+    return c
+
+
+@gf.cell
+def piezo_transducer_coupler(
+    pad_size: tuple[float, float] = (300.0, 200.0),
+    pad_gap: float = 30.0,
+    feedline_length: float = 200.0,
+    cross_section: CrossSectionSpec = "cpw",
+    layer_metal: LayerSpec = LAYER.M1_DRAW,
+    layer_piezo: LayerSpec = LAYER.IND,
+) -> Component:
+    r"""Piezoelectric coupling pad for piezo-optomechanical transduction.
+
+    Creates the microwave side of a piezo-optomechanical transducer.
+    The layout consists of two large interdigitated metal pads that
+    generate a strong electric field across a piezoelectric material
+    (e.g. AlN or LiNbO₃) placed on top or bonded via flip-chip.  The
+    electric field drives a mechanical resonance that is simultaneously
+    coupled to an optical cavity via radiation pressure.
+
+    .. svgbob::
+
+         CPW feedline
+        o1 ───────────┐
+                      │
+                ┌─────┴─────┐
+                │           │
+                │   pad 1   │  ← metal on SC chip
+                │           │
+                ├───gap─────┤  ← piezoelectric
+                │           │
+                │   pad 2   │  ← metal on SC chip
+                │           │
+                └─────┬─────┘
+                      │
+        o2 ───────────┘
+         CPW feedline
+
+    See :cite:`mirhosseiniQuantumTransductionOptical2020` for experimental
+    details of a piezo-optomechanical quantum transducer.
+
+    Args:
+        pad_size: (width, height) of each metal pad in µm.
+        pad_gap: Gap between the two pads (piezoelectric region) in µm.
+        feedline_length: Length of CPW feedline sections in µm.
+        cross_section: Cross-section specification for CPW feedlines.
+        layer_metal: Metal layer for the coupling pads.
+        layer_piezo: Layer to mark the piezoelectric coupling region.
+
+    Returns:
+        Component with ports ``o1``, ``o2`` (CPW feedline) and
+        ``piezo_coupler`` (placement port at the piezo gap centre).
+    """
+    c = Component()
+
+    pad_w, pad_h = pad_size
+
+    # --- Top metal pad ---
+    top_pad = c.add_ref(gf.components.rectangle(size=(pad_w, pad_h), layer=layer_metal))
+    top_pad.dmove((-pad_w / 2, pad_gap / 2))
+
+    # --- Bottom metal pad ---
+    bot_pad = c.add_ref(gf.components.rectangle(size=(pad_w, pad_h), layer=layer_metal))
+    bot_pad.dmove((-pad_w / 2, -pad_gap / 2 - pad_h))
+
+    # --- Piezo coupling region marker ---
+    piezo_region = c.add_ref(
+        gf.components.rectangle(size=(pad_w, pad_gap), layer=layer_piezo)
+    )
+    piezo_region.dmove((-pad_w / 2, -pad_gap / 2))
+
+    # --- CPW feedlines extending horizontally from pad sides ---
+    feed_left = c.add_ref(straight(length=feedline_length, cross_section=cross_section))
+    feed_left.dmove((
+        top_pad.dbbox().right - feed_left.ports["o1"].dcenter[0],
+        top_pad.dcenter[1] - feed_left.ports["o1"].dcenter[1],
+    ))
+
+    feed_right = c.add_ref(
+        straight(length=feedline_length, cross_section=cross_section)
+    )
+    feed_right.drotate(180)
+    feed_right.dmove((
+        bot_pad.dbbox().left - feed_right.ports["o1"].dcenter[0],
+        bot_pad.dcenter[1] - feed_right.ports["o1"].dcenter[1],
+    ))
+
+    # --- Ports ---
+    c.add_port(name="o1", port=feed_left.ports["o2"])
+    c.add_port(name="o2", port=feed_right.ports["o2"])
+
+    c.add_port(
+        name="piezo_coupler",
+        center=(0, 0),
+        width=pad_w,
+        orientation=90,
+        layer=layer_piezo,
+        port_type="placement",
+    )
+
+    # --- Metadata ---
+    c.info["pad_width"] = pad_w
+    c.info["pad_height"] = pad_h
+    c.info["pad_gap"] = pad_gap
+    c.info["transducer_type"] = "piezo_optomechanical"
+
+    return c
+
+
+if __name__ == "__main__":
+    from qpdk import PDK
+
+    PDK.activate()
+
+    show_components(electro_optic_transducer, piezo_transducer_coupler)