Inter-universe machine

The inter-universe machine (also mistakenly called the 'inter-dimensional machine', even though inter-dimensional means to travel between different physics-realms and inter-universe means to travel between different universes) is a theoretical concept for a machine capable of hopping between multi infinite loop universes.

Theoretical physics
The theory is, if multi infinite loop theory is true, then it's possible to travel from one universe to another simply by either travelling backwards or forwards in time, skipping over various loop iterations.

Limitations
The problem is how to overcome the expansion-contraction barrier, as the inter-universe time-machine would have to be able to withstand the crushing super-gravity generated during the contraction phase of the last stages of the iteration and survive the large-scale outward explosion after the contraction phase ended (ignoring issues like air, food, water supplies and physical location during time-shift, as the target destination may actually shift position due to the differing nature of the multi-infinite loop).

Possible solutions to limitations
Possible solutions include point-to-point quantum teleportation (as quantum particles are entangled over time) which negates the requirement for an actual device, but renders it a one-way trip suspect to failure and little feedback for error-correction (unless a self-dematerialising quantum teleportation system could be devised). This also assumes the quantum particles are not 'reset' during the contraction-expansion stage.

Other solutions include a micro-tunnel formed of quantum particles of which search for any unusual electromagnetic signals in the approximate location of earth, and uses it to 'home in' on earth in the new iteration (with the micro-tunnel being moved progressively closer to earth). This excludes the possibly of ending up on an earth-variant with no life or insufficient technology (or technology technical enough to bypass electromagnetic broadcasting altogether) and thus reduces error-rates to acceptable levels.

The micro-tunnel can then be used to pick up wireless signals to monitor alternate-iteration earth without necessarily visiting (even allowing for two-communications and possibly a two-way time-teleportation system).