[Circuit renderer] Compact rendering of classically controlled gate

[Dima Fedoriaka (fedimser)]

• In JSON model (circuit.rs/circuit.ts) added classical_controls to represent classical controls of a gate.
• In rust, if there is a then/else branch with condition "resullt==One" or "result==Zero" and all gates inside have single target and no controls, instead of generating a group, emit gates without grouping them, but with added classical control.
• In typescript, add a code to render classically controlled gate.
• Add circuit-to-Q# conversion for classically controlled gate.
• Add circuit-to-string rendering for classically controlled gate.

Example 1 - teleportation

Before:

After:

Example 2

operation Tmp1() : Unit {
    use q = Qubit[4];

    H(q[0]);
    let m0 = M(q[0]);
    if (m0 == One) {
        X(q[1]);
    } else {
        X(q[2]);
        Z(q[2]);
    }
    let m1 = M(q[1]);
    if (m0 == Zero) {
        Rx(0.5, q[3]);
    } else {
        Ry(0.5, q[3]);
        if (m1==Zero) {
            X(q[1]);
        }
    }
}

Example 3 - negative cases (controlled gate, complex condition, 2-qubit gate).

operation Tmp2() : Unit {
    use q = Qubit[4];
    
    H(q[0]);
    H(q[1]);
    let m0 = M(q[0]);
    let m1 = M(q[1]);

    if (m0 == Zero) {
        CNOT(q[2], q[3]);
    }
    if (m0 == One and m1 == One) {
        X(q[1]);
    }
    if (m0 == Zero) {
        Rxx(0.5, q[2], q[3]);
    }
}

[Copilot]

Pull request overview

Adds first-class support for “compact” classically controlled gates across the Rust circuit model, rendering pipeline, and circuit-to-Q# conversion, so simple if (result == One/Zero) branches can be visualized as gates annotated with classical controls (rather than expanded conditional groups).

Changes:

• Extend the circuit JSON/schema and Rust circuit model with classicalControls for unitary operations.
• Update circuit tracing/lowering and renderer logic to emit and draw compact classically controlled gates (including inverted/“anti” controls).
• Add/adjust Rust, JS/TS, Python, and snapshot tests to cover compact classical control behavior and updated output sizes.

Reviewed changes

Copilot reviewed 26 out of 27 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
source/samples_test/src/tests/OpenQASM.rs	Update expected circuit-length snapshot for teleportation due to compact rendering.
source/samples_test/src/tests/getting_started.rs	Update expected circuit-length snapshot due to compact rendering.
source/samples_test/src/tests/algorithms.rs	Update multiple expected circuit-length snapshots due to compact rendering.
source/qdk_package/tests/test_qsharp.py	Update expected ASCII circuit strings for compact classical control rendering.
source/qdk_package/tests/test_qasm.py	Update expected ASCII circuit strings for compact classical control rendering.
source/npm/qsharp/ux/qsharp-circuit.css	Add styling for inverted (anti-) classical control dots.
source/npm/qsharp/ux/circuit-vis/utils.ts	Include classicalControls registers in register collection for sizing/renumbering.
source/npm/qsharp/ux/circuit-vis/renderer/process.ts	Map classicalControls into render data and ensure they’re included in classical-control register tracking.
source/npm/qsharp/ux/circuit-vis/renderer/gateRenderData.ts	Add render-data shape for compact classical controls on a gate.
source/npm/qsharp/ux/circuit-vis/renderer/formatters/gateFormatter.ts	Render compact classical control connectors/dots alongside gates.
source/npm/qsharp/ux/circuit-vis/actions/circuit-actions/classicalRefs.ts	Treat classicalControls as classical consumers for cascade/move/delete logic.
source/npm/qsharp/test/circuits-cases/if-else.qs.snapshot.html	Update SVG snapshot to reflect compact classical control rendering.
source/npm/qsharp/test/circuit-editor/utils.test.mjs	Add coverage ensuring compact classical controls affect wire extent calculations.
source/npm/qsharp/test/circuit-editor/process.test.mjs	Add coverage ensuring processOperations maps compact classical controls into render data.
source/npm/qsharp/test/circuit-editor/gateFormatter.test.mjs	Add coverage ensuring compact classical controls render connectors and (anti-)dots.
source/npm/qsharp/test/circuit-editor/circuit-actions/measurementCascade.test.mjs	Extend cascade tests to include compact classical control consumers.
source/npm/qsharp/src/data-structures/circuit.ts	Add ClassicalControl type + runtime validation and wire into Unitary.
source/compiler/qsc/src/interpret/circuit_classical_ctl_tests.rs	Update expected interpreter circuit output to reflect compact classical controls.
source/compiler/qsc_circuit/src/rir_to_circuit/tests/logical_stack_trace.rs	Update/add logical trace expectations for compact classical control behavior (+ negative cases).
source/compiler/qsc_circuit/src/rir_to_circuit.rs	Emit compact classical controls for simple if branches when safe (single-qubit, uncontrolled gates).
source/compiler/qsc_circuit/src/circuit/tests.rs	Add circuit layout/string rendering test for direct classical control wire range.
source/compiler/qsc_circuit/src/circuit.rs	Add classical_controls to the Rust circuit model + include in display/layout and serialization.
source/compiler/qsc_circuit/src/circuit_to_qsharp/tests.rs	Add test coverage for circuit-to-Q# conversion of compact classical controls.
source/compiler/qsc_circuit/src/circuit_to_qsharp.rs	Generate Q# if wrappers for unitaries with compact classical controls; disable Ctl+Adj when present.
source/compiler/qsc_circuit/src/builder/tests.rs	Add test ensuring classical control result-ids are converted to classical registers.
source/compiler/qsc_circuit/src/builder.rs	Thread classical control inputs through gate building into circuit operations.

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[Scott Carda (ScottCarda-MS)]

I wonder if we could have a more general approach and have all controls fall under the controls field. The type of that field would be modified to be (Register | ControlValue)[] with ControlValue being the rename for ClassicalControl. That would leave open the ability to specify inverted quantum controls also.

[Scott Carda (ScottCarda-MS)]

Or better yet, for the type, it would be a Control[] with

export interface Control extends Register {
  inverted?: boolean;
}

[Scott Carda (ScottCarda-MS)]

Since this is a change to the data contract for circuits, we should consider bumping the circuit version number and making sure we have a plan to auto-update old circuit files for backwards compatibility.