Yes, you are correct. In the double-slit experiment with single molecules, it is possible to perform "which-path" measurements or gather information about which slit the molecule passes through without completely destroying the interference pattern, unlike the case with single electrons.
This phenomenon is often referred to as "quantum eraser" or "delayed-choice quantum eraser" experiment. In this modified version of the double-slit experiment, additional elements are introduced to gather information about the path of the molecules while still allowing interference to occur.
The key idea behind the quantum eraser experiment is that the information about the path of the particles can be "erased" or made inaccessible, which leads to the reappearance of the interference pattern. It demonstrates the counterintuitive nature of quantum mechanics.
In the setup of the quantum eraser experiment, detectors are placed near the slits to determine which slit the molecule passes through. However, these detectors do not directly provide information about the path of the molecule. Instead, they are entangled with another set of particles called "ancilla" particles. The entanglement allows for the correlation between the path information and the interference pattern to be established.
Importantly, the information obtained from the detectors is not immediately used or observed. It is only when the entangled ancilla particles are measured that the which-path information becomes available. However, by manipulating the measurements of the ancilla particles in a specific way, it is possible to "erase" or scramble the which-path information. As a result, the interference pattern reappears on the screen, as if the path information was never obtained.
The quantum eraser experiment highlights the intricate nature of quantum mechanics and the role of measurement in collapsing the wave function. It demonstrates that the act of gathering information about the path of particles can have an impact on their behavior and the resulting interference pattern.