How to get all options for QuantumCircuitOperator?

Questions
1

In the internet I can find such options which is not listed in the help menu, Wolfram
Documentation. How can I find all options for a given command?

For example I can find the “Diagram” option in the help menu for QuantumCircuitOperator but “HorizontalGapSize” is not in the help menu I have found it on the internet and it works in my code.

2

QuantumCircuitOperator doesn’t have options of its own. The “Diagram” property is calling the internal CircuitDraw function, you can get its exclusive options after filtering out some System options that it also takes:

FilterRules[
 Options[Wolfram`QuantumFramework`PackageScope`CircuitDraw], 
 Except[Join[Options[Graphics], Options[Style], Options[Rectangle]]]]

;

{"WireLabels" -> Automatic, "MeasurementWireLabel" -> "c", 
 "ShowWires" -> True, "ShowLabel" -> False, 
 "ShowMeasurementWire" -> True, "ShowEmptyWires" -> True, 
 "ShowOutline" -> False, "SubcircuitLevel" -> 1, 
 "GateOverlap" -> False, "MeasurementWirePosition" -> Top, 
 "HorizontalGapSize" -> 1, "ShowGateLabels" -> True, 
 "SubcircuitOptions" -> {}, "ShowExtraQudits" -> False, 
 "RotateGateLabel" -> Automatic, "GateLabels" -> {}, "Size" -> 0.75, 
 "VerticalGapSize" -> 1, "GateBackgroundStyle" -> Automatic, 
 "GateBoundaryStyle" -> Automatic, "GateShapeFunction" -> Automatic, 
 "ShowConnectors" -> False, "ShowGlobalPhase" -> True, 
 "WireStyle" -> Automatic, "ThickWire" -> False, 
 "DimensionWires" -> True, "IdentityGate" -> False, 
 "Arrowhead" -> 0.005, "Label" -> Automatic, "ShowGauge" -> True, 
 "LongOuterWires" -> True, "ShowWireEndpoints" -> False, 
 "ShowWireDimensions" -> False, 
 "OutlineStyle" -> 
  Directive[
   EdgeForm[
    Directive[Dashing[{Tiny, Tiny}], RGBColor[
     0.537254, 0.537254, 0.537254], Opacity[0.8]]], FaceForm[
RGBColor[0.898039, 0.898039, 0.898039, 0.3]]], 
 "BarrierStyle" -> Automatic}