A controversial team of physicists say they are about to conduct a series of quantum tests to try to determine whether we are living in a simulation or not. 

We live in a real universe, as far as we can tell – but to be fair it's a pretty weird one. In the quantum world, things really get strange. One particular oddity is shown in the double slit experiment, which has been puzzling physicists for nearly a century, and which the team plans to exploit in their test of whether the world is really real.

When you shine a light through two slits on a screen, it creates an interference pattern where the waves interfere with each other on the other side of the slit. When it was first discovered, this was evidence that light behaves as a wave. But if you fire photons (or electrons, or even some molecules) individually at the screen, which scientists have done, eventually you will still get an interference pattern. It's as if a single photon went through both slits as a wave, which then collapsed itself.

It gets weirder. If you design your experiment with detectors so that you know which way the photon passed through, the interference pattern does not emerge. Physicists have been puzzling over this for a long time, and have a number of explanations, each with their own degree of weirdness. In the many worlds interpretation, for weirdest example, every time we measure a system in a superposition of many different possible states, we see only one version when we measure it, and the rest plays out in another universe. In others, such as pilot wave theory, the particle we measure rode in on a wave.

Quantum mechanics is difficult, but is our best interpretation of the small world, and physicists continue to work on the problem. Some believe that observation is important to the collapse of the wave function, while others think there is a physical solution which we haven't got our heads around just yet. We see weird results all the time, and many of them are misinterpreted.

But one controversial (and likely incorrect) idea is that reality is a simulation, and that we only see it when it is rendered to us. 

In 2017, a group of physicists proposed a few methods of finding out in their paper "On Testing the Simulation Theory" with varying degrees of complexity. Their idea rests on the assumption that the simulation would have limited resources, and so isn't simulating everything in the universe all at the same time. As such, the simulation would act much like a computer game, only rendering the parts of the simulation that are being observed by a "player" at the time. Sort of like how in some video games, the entire observable universe off-screen is not rendered to save on computer power (a wise move).

The key to finding out whether we are in a simulated universe or a real one, according to the team, is to find out when information becomes available to us, the observers.

"To save itself computing work, the system only calculates reality when information becomes available for observation by a player, and to avoid detection by players it maintains a consistent world, but occasionally, conflicts that are unresolvable lead to VR indicators and discontinuities (such as the wave/particle duality)," the authors wrote in the paper, posted to pre-print server arXiv. 

Should it only be at the time of observation by an observer (and not the apparatus), the team suggests this would be evidence that it is only being "rendered" at the point of observation, meaning that we are living in a simulation. 

By using a series of abstractions, they propose that it might be possible to find (should we live in a simulation) that the information is only given to us at the point of observation. To do this, they aimed to create versions of the double-slit experiment that would show us when information becomes available to us.

“Two strategies can be followed to test the simulation theory," the team, led by Thomas Campbell, a former applied physics scientist for NASA and the Department of Defense, explains in the paper. "1: Test the moment of rendering. 2: Exploit conflicting requirement of logical consistency preservation and detection avoidance to force the VR rendering engine to create discontinuities in its rendering or produce a measurable signature event within our reality that indicates that our reality must be simulated."

In one of the simplest of their proposed experiments, the which-way data and screen data are collected on two separate USB drives, and not seen by an experimenter. Keep doing this, and you have a lot of flash drives that contain which-way data, and screen data. You then destroy the which-way data USBs based on a coin flip.

"Destruction must be such that the data is not recoverable and no trace of the data is left on the computer that held and transferred the data. For n even, one can replace the coin-flipping randomization by that of randomly selecting a subset composed of half of the pairs of USB flash drives containing which-way data for destruction (with uniform probability over such subsets)," they say in the paper.

"The test is successful if the USB flash drives storing impact patterns show an interference pattern only when the corresponding which-way data USB flash drive has been destroyed."

So, if you open up the screen data and see wave patterns when the corresponding which-way USB stick has been destroyed, that would mean that the simulation had rendered reality at the point of observation (you opening the file) and not when observed by the detector. 

The team proposed other more complicated versions of the experiment, which are available in their paper. 

While a fun idea to think about in science fiction, the team actually raised money via a Kickstarter to actually perform the experiment. It is not clear which experiment they have chosen to go ahead with, but the team explained that the tests are being carried out at California State Polytechnic University (CalPoly), Pomona. A Canadian university also involved in the research has chosen to stay anonymous, according to a press release.

"The idea here is that consciousness is not a product of the simulation — it is fundamental to reality,” Campbell said in the press release. “If all five experiments work as expected, this will challenge the conventional understanding of reality and uncover profound connections between consciousness and the cosmos.”

While big talk, it would take some seriously impressive and replicable results to upend anything, let alone provide evidence that we are living in a simulation. Results, in the unlikely event that they are interesting, will be open to interpretation, just like all the other strange results of quantum experiments. Quantum mechanics is weird, and people have gotten very carried away while thinking about the double slit experiment, and thought experiments like Schrödinger's cat. 

These things are difficult to interpret, but there are a rich variety of explanations for what we observe better than that we are in a crummy simulation with a limited amount of power, rendering reality to us at the moment of observation.