Scientists can now simulate curved space-time in a lab

When discussing quantum physics, you’ll often hear a the phrase “quantum field theory” thrown about. This refers to the general idea that quantum particles are actually just localized excited states of a more general quantum field underlying them — a trippy but mathematically useful idea that interacts with Einstein’s classical conception of space-time in ways that are complex, to say that least. Gravity, so says dogma, is the result of curvature in the ineffable medium of space-time, and modern quantum physics says that curved space-time ought to effect the behavior of a hypothetical quantum field somehow. Precisely how they interact is an open question, and answering that question has been described as the holy grail of physics. It’s currently very difficult to study those interactions in the lab, but that may be about to change.

This light-bending experiment proved that space-time curvature affects light.

Curving space-time is very difficult to do, synthetically. It’s easy enough through the classical means — collect a bunch of mass somewhere — but to generate a curve steep enough to have measurable effects on single quantum particles requires densities found only near black holes and the like. Curving space-time in a more direct way, with magnetic fields or “exotic matter,” has been proposed in halls as hallowed as those at NASA — but such technology would allow us to build a literal warp drive, and  if mankind had figured that out you’d have read about it here by now. No, instead of figuring out how to actually curve space-time, a German researcher named Nikodem Szpak may have found a loophole that lets us study the effects of curved space-time without having to actually curve it.

To go forward with this story, you’ll need to either acquire a high-level mathematics degree or accept the following statement on trust: ultra-cold atoms (and since heat is just atomic movement, you can essentially read that as ultra-stationary atoms) caught in a very specific optical lattice (laser-field) behave overall in a way that can be related to the movement of quantum particles through space-time. That’s a big statement, so let’s go through it piece by piece.

Note that the balls naturally “fall” into the low-energy valleys in the optical interference pattern.

First, the atoms and the lattice. This technique uses multiple lasers to essentially create complex interference patterns with deliberately spaced peaks and valleys — areas of high or low energy intensity. The ultra-cooled atoms will naturally fall into the valleys due to thermodynamics — and while they are ultra-stationary, quantum mechanics says they should still be able to “tunnel” from place to place. The atoms must be ultra-cold so that all or virtually all their movement is due to this tunneling effect alone. If it is, then the overall pattern of movement through the lattice can represent the interaction of quantum fields and space-time.

Really, the only other fact to internalize here is that, by tailoring the lattice to create a very specific pattern of peaks and valleys in which the atoms may move, the researches can change the values for their space-time metaphor. One lattice might simulate the quantum field’s interactions with flat space-time (which technically doesn’t exist but which would be most closely found in deep, deep, deep space far from any large masses), while another might simulate a highly warped area of space, like a spot very near the surface of a star.

The possible effects of this research are prosaic, at least in the short term. This is one of those intersection breakthroughs, the sort that doesn’t really get you anywhere but rather opens up many new avenues of research. Being able to study the interaction of quantum field theory and general relativity (gravity), even indirectly like this, could inform work on everything from space thrusters to a grand unified theory of the universe.

Changing the optical pattern changes the mathematical metaphor for space-time.

By using a metaphor for space-time curvature, rather than changing that curvature directly, the researchers could give future scientists a way to simulate the state of space-time at the event horizon of a black hole, or during the very earliest instants after the Big Bang. All that would be required is the correct interference pattern to control the distribution of the most probable tunneling spots (valleys). And by slowly changing the interference pattern over time, researchers could even watch the effects of continuous variation in that space-time — say, due to expansion in the universe’s earliest moments. Note that there is a lot to study about quantum fields and space time that doesn’t have to do with such small-scale movements of quantum particles, and this technique wouldn’t be much use in studying those. This is certainly not the end of Einstein’s beef with quantum physics.

There’s no way to predict how physicists might apply this breakthrough, but whatever they come up with could very well be monumental. The interaction between quantum phenomena and general relativity is basically the holy grail of modern high-level physics, and it may have just gotten a whole lot easier to study. Could this be the underpinning of some future Grand Unified Experiment? Possibly. More likely, it will inform the modern understanding of quantum and relativistic physics, and hopefully bring them closer to uniting once and for all.

Source: http://www.extremetech.com