Jake Gyllenhaal and Jeanne Cadieu just reached a major milestone.The 40-year-old actor and his longtime girlfriend made their red carpet debut as a couple. The two posed together with Peter Sarsgaard and Maggie Gyllenhaal at the premiere of during the New York Film Festival earlier this week.To support his sister, Jake was stylishly dressed in a dark green velvet suit, while his lady love wore a cream-colored long-sleeved dress.