[Solved]-Opening UI5 Quickview by non-SAPUI5 control-d3.js

Everything you describe seems to be correct. According to the documentation of sap.m.Popover you can also call openBy with a DOM reference as parameter.

What you are passing in your code snippet is not a DOM reference however, it is a d3 selection. To get the required DOM reference from the selection you have to add [0][0](see this answer).

function openQuickView(circleClicked) {
  quickViewPage.setHeader(circleClicked.created_by);
  quickView.openBy(d3.select(circleClicked)[0][0]); 
};

EDIT: After playing around with the provided fiddle I found the problem. The parameter to the function is the datum of the clicked object, not the DOM. You should change your click handler and the function like this:

svg.selectAll("circle")
// ...
.on("click", function(d) {
  openQuickView(this, d);
});
function openQuickView(circleClicked, circleData) {
  quickViewPage.setHeader(circleData.created_by);
  quickView.openBy(circleClicked);
}