Skip to content

Step 2: Design a Quantum-RF Circuit

In this step, we'll explore a quantum-RF PDK component, simulate it, and then create a transmon with resonator circuit by drawing the schematic, reviewing the layout, and connecting components together.

Before you get started, create a new sample project and select the quantum-rf-public-main sample project.

Explore and simulate a resonator

  1. In the Visual Studio Code sidebar, select the GF+ tab. Click the Create Schematic button and type quarter_wr_simulation for the name, then press Enter.

    Create schematic

  2. In the Schematic View, click the Add Component tool (or click it in the bottom toolbar), then search for quarter_wave_resonator_coupled from the qpdk library and select the desired component.

    Add resonator

  3. In this view, you can see the ports of the component coupling_o1 (P1) and the output coupling_o2p(P2). Before running a simulation, we have to select the ports that we want to use. Click the Port button in the bottom bar and then click in the coupling_o1and coupling_o2ports. The rotation of the port can be changed with the key R. Then click the Simulate button in the top-right corner to run a simulation.

    Resonator ports

  4. The simulation panel opens with SAX S-parameter results. Click Simulate to run. You can toggle on-off additional S-parameter combinations (P1 ↔ P1, P2 ↔ P1, P2 ↔ P2).

    Simulation results

  5. With only P1 ↔ P2 selected, you can zoom in to see the resonance at ~7.537 GHz.

    Resonance detail

Create the transmon circuit schematic

  1. Go back to the GF+ tab and create a new schematic. Name it transmon_with_resonator_2, then press Enter.

    Create transmon schematic

  2. Using the Add Component tool, add the following components:

    • double_pad_transmon_with_bbox
    • resonator
    • plate_capacitor_single

    Right-click in the plate_capacitor_single instance to see its parameters and edit its values: set the length to 250 and the width to 80.

    Plate capacitor settings

  3. Once all components are placed, click Open in Livewire in the top-right corner to open the layout editor.

    Show GDS

Arrange and connect components

  1. In the Layout View, use the select tool to rearrange the components. Position the resonator (X2) on the left and the transmon (X1) on the right, with the plate capacitor (X3) nested inside the transmon.

    Arrange layout

  2. Select the Route (w) tool in the layout toolbar, then draw a Manhattan route between the resonator and the transmon pad. First click on the initial port, and then click in the desired waypoints.

    Route in layout

  3. A good practise is to define first in the schematic the intended connections. Switch to the Schematic View and select the Wire tool. Draw connections between the resonator and the plate capacitor to define the circuit netlist.

    Schematic connections

  4. Back in the Layout View, connections that exist in the schematic but are missing in the layout are shown as red double-arrow lines. Hover over one to see the tooltip — you can then right-click to auto-route with Playdough or click the Auto-route button.

    Missing connection

  5. After auto-routing, the resonator and transmon are fully connected.

    Playdough routed

Continue to: Step 3a: Check for Design Errors - DRC