The deal was announced back in June, when the group was originally called Infinity Racing, but since then progress in concluding it has been slow.
If it does not come off, then the team is expected to conclude a deal with Pastor Maldonado because of his backing from PDVSA.
With team boss Eric Boullier admitting that the matter needs sorting soon, because there is a risk that Hulkenberg could sign for someone else, Lopez said on Friday that he remained confident over Quantum.
"We have preliminary agreements with the company we want to partner with, and we're just waiting for this to be concluded," said Lopez, in an interview published on the Lotus website. "This is a very detailed process.
"The history is that we decided to offer a minority stake to an investor. We consider this approach as the best way forwards, just like any other Formula 1 team.
"Deals like this do not move at the speed we're used to in Formula 1 and we're hopeful that we'll conclude it in the near future.
"With our current performance on track and the fact that there are very few Formula 1 teams that can offer an investment opportunity like we do we are constantly being contacted by interested parties, but for now we are pursuing our preferred option."