What I've read on various sites is to let them die back naturally without tying back. The reasoning is that the more surface area of the plant that is exposed to the sun, the more food the bulb can store for the next year's blooms. Some people treat tulips as annuals, in which case you could probably go ahead and cut them down or dig them out. If not, I'd leave the leaves alone. Can you mulch around the stems until time to cut them back?

The famous Filoli gardens in Woodside California puts in large beds of tulips inter seeded with Cynoglossum amabile, which grow to about 2 feet tall with airy blue flowers. They are very effective in concealing the tulips after the bloom. The timing in their case is just right and the tulip and cover crop are all planted at the same time. Al

If you tie them up or otherwise block their access to the sun you will reduce the vigor of the plant and you may not get flowers next year.

They should be unmolested. I cover mine up with various perennials.