Quantum. Computers.
Once we get steady, even little bit bigger scaled quantum computer working, we can easily, I mean easily simulate an entire universe, setting just the right balance gravity and other forces. We can even test and see some new things that it would need to have an universe, and even find them from our own universe if trying to search them at best.
Have that happening, this theory will most definitely become one of the most important ones. As in the simulated universe, assuming intellectual life takes place in there, how could those simulated beings ever know they're in simulation.
It is referred in many sources, that stable quantum computer with 300 fully entangled qubits can manipulate as many classical bits of information as there are atoms in the Universe.
As stated in gizmag article about quantum computers:
Taking that into account, this universe could be simulated in chip sized of a... chip. Just with more than 300qbits. There could even be virtual universes inside virtual universes. This should get you all geeks learning VMWARE
There are already working quantum computers, just not powerfull enough for that kind of simulation - yet.
Source
If the simulation only sets the laws of nature right and just lets it run (many times perhaps, countless times) it will end up in universe like ours - without any work of coding. Just set the rules and let the possibilities happen. That is why it will look perfect, because it is, and not even written in that manner, just a possibility capitalizing under the set rules of nature. Works to same way that winning a lottery. If you make 15 million different rows, you have 100% chance of one of them being right (finnish lotto). With large quantum computer power, it could be very possible. There could be quadrillion times billion quadrillion universes that wouldn't be like this, but there would be scenarios where it happens like it happens here, if we make simulation based on just running it on given laws on its own.
Hell, we could even find all the needed laws by just on running simulations on all possible law sets of nature as long as we find a stable set of rules from perspective of life.
Time could be scaled any how we like. We could simulate 1 second in our universe to mean 10000000000 years in the simulated universe. This could also be true for our reality if it is simulated, and it might be we last just an hour for "higher reality" time as an universe. Today, we have high speed camera footage of almost planck lenght of time. There you can see a beam of light traveling distance of a coca cola bottle and it takes minutes, you can find that on youtube, too. Here it is presented in a ted talk (forwarded it a bit for you). You will see the actual footage in this ted talk, too.
https://youtu.be/Y_9vd4HWlVA?t=1m29s
You must understand that we can simulate million years in 0,0001 second if we wish to make it that way with powerfull enough (quantum) computer. Time is experiened individually. How can we know how long a year feels for a say dog? We can literally stare 0,0001 second footage for minutes when we have enough photos taken per second as shown in the video. It really brings into this reality what is relativity of time as an experience.
This could also mean few things that pop into my mind now:
1) If the chip we or any universe is simulated at crashes, everything will disappear and we will feel nothing.
2) There might equally possibly be simulated life after death in that simulated universe (if the chip doesnt crash). The one who created it might as well added it, even if the realest of real reality wouldn't actually have that. It would be equally possible to Odin exist or not, or equally possible that what ever we believe in we see / get in afterlife, or equally possible that the maker of quantum computer just didin't code anything for afterlife. However, the last seems little less likely to me, because that would be a boring thing to do. As a coder of universe, the afterlife would be probably even more interesting thing to do.
3) This simulated universe would end the endless discussion about what was before big bang to trigger it. Simply some coder, perhaps beareded guy lying on cloud, pressed a button and it happened. It would offer an exact answer to question of how the hell is it even possible that we are here.
On top of everything, nature of quantum computer is great for simulating an universe, where you just simulate endless possibilities happening the way or another. That is exactly the nature of quantum computer, that is great for analysing mass data and simulating big scale things, simulating things that are based on so called randomness (lots of possibilities and just some happening unpredictably).
If you are interested in quantum computers study about them in youtube with keywords such as quantum computer of D-wave (the googles quantum computer). There are other makers too.
https://youtu.be/DZ2DcILZAbM?t=1m45s