Exactly. Less of a question and more of a topic for debate. Can it be done
The easy side, gravity will pull an object towards the earth at no cost.
The hard part is how to return the weight to its starting point using less energy than what was created by the downwards motion.
Factors are friction, air resistance.
Without both you would be at an equal energy output, (is my thinking.)
Air resistance is easier to combat as you would put it into a vacuum.
Friction is the hard part.
As for the equal energy output, you would need a way to increase the weight/force applied at the top of the experiment or reduce the weight/force applied at the bottom.
If you can increase the length of the object at the top of the revolution and decrease it at the bottom would you have more force applied during the downwards motion?