Fix modifier at U

visitor/const.go

@@ -2,6 +2,8 @@ package visitor
 
 import "math"
 
+const U string = "U"
+
 var Const = map[string]float64{
 	"pi":    math.Pi,
 	"tau":   2 * math.Pi,

visitor/visitor.go

@@ -312,41 +312,26 @@ func (v *Visitor) Params(xlist parser.IExpressionListContext) ([]float64, error)
 }
 
 func (v *Visitor) Modify(u matrix.Matrix, qargs []q.Qubit, modifier []parser.IGateModifierContext) (matrix.Matrix, error) {
-	var ctrl, negctrl []q.Qubit
 	for i, mod := range modifier {
-		// https://openqasm.com/language/gates.html#inverse-modifier
-		// The inverse of a controlled operation is defined by inverting the control unitary. That is, inv @ ctrl @ U = ctrl @ inv @ U.
-
 		n := v.Visit(mod).(int64)
 		switch {
 		case mod.CTRL() != nil:
-			ctrl = append(ctrl, qargs[i])
+			u = AddControlled(u, i)
 		case mod.NEGCTRL() != nil:
-			ctrl, negctrl = append(ctrl, qargs[i]), append(negctrl, qargs[i])
+			n := v.qsim.NumberOfBit()
+			x := gate.TensorProduct(gate.X(), n, []int{i})
+
+			u = AddControlled(u, i)
+			u = matrix.Apply(x, u, x)
 		case mod.INV() != nil:
 			u = u.Dagger()
 		case mod.POW() != nil:
-			// TODO: ctrl @ pow(0.5) @ U is not equal to pow(0.5) @ ctrl @ U
 			u = matrix.ApplyN(u, int(n))
 		default:
 			return nil, fmt.Errorf("modifier=%s: %w", mod.GetText(), ErrUnexpected)
 		}
 	}
 
-	switch len(ctrl) {
-	case 0:
-		n := v.qsim.NumberOfBit()
-		u = gate.TensorProduct(u, n, q.Index(qargs...))
-	default:
-		n := v.qsim.NumberOfBit()
-		u = gate.Controlled(u, n, q.Index(ctrl...), qargs[len(qargs)-1].Index())
-
-		if len(negctrl) > 0 {
-			x := gate.TensorProduct(gate.X(), n, q.Index(negctrl...))
-			u = matrix.Apply(x, u, x)
-		}
-	}
-
 	return u, nil
 }
 
@@ -364,14 +349,17 @@ func (v *Visitor) Builtin(ctx *parser.GateCallStatementContext) (matrix.Matrix,
 
 	id := v.Visit(ctx.Identifier()).(string)
 	switch id {
-	case "U":
+	case U:
 		params, err := v.Params(ctx.ExpressionList())
 		if err != nil {
 			return nil, false, fmt.Errorf("params: %w", err)
 		}
+		qargs := v.Visit(ctx.GateOperandList()).([][]q.Qubit)
+
+		n := v.qsim.NumberOfBit()
 		u := gate.U(params[0], params[1], params[2])
+		u = gate.TensorProduct(u, n, q.Index(flatten(qargs)...))
 
-		qargs := v.Visit(ctx.GateOperandList()).([][]q.Qubit)
 		u, err = v.Modify(u, flatten(qargs), ctx.AllGateModifier())
 		if err != nil {
 			return nil, false, fmt.Errorf("modify: %w", err)