Quantum State Created In Largest Object Yet 265
SpuriousLogic writes "A team of researchers have created a 'quantum state' in an object billions of times larger than ever before. From the article: 'Such states, in which an object is effectively in two places at once, have until now only been accomplished with single particles, atoms and molecules. In this experiment, published in the journal Nature, scientists produced a quantum state in an object billions of times larger than previous tests. The team says the result could have significant implications in quantum computing.'"
A Bose-Einstein Condensate? (Score:4, Interesting)
From what the article looks like, all they've done is created a BEC (They don't mention that in the article, am I off?) of the largest object yet, which just means they cooled the material to milli-kelvin using some kind of trap, and the material becomes a new state of matter, a Bose Einstein Condensate.
For some reason, I expected some kind of two-slit or uncertainty principle thing with a very large object. This doesn't really seem that impressive to me, but then my quantum is a bit dated.
How do they confirm it's in a quantum state? (Score:5, Interesting)
I have a question that I assume has a reasonable answer, just one I've never actually gotten confirmation on.
Once they've placed this object in a quantum state, how do they verify that it's "occupying two states at once?" Do they just measure it and repeat the process several times, and note that it's occasionally at 1 quanta, occasionally at 0, and from that infer that it was in a quantum state up until they measured it?
Second question, while I'm here - am I right in saying that according to the many-worlds interpretation, the universe branches when this object enters a quantum state, and we end up in one of two universes, one where the object has 1 quanta of energy and one where it has 0?
Trying to grok all this "quantum mechanics" stuff :)
What I don't understand is...... (Score:1, Interesting)
What really confuses me about this (Do not know much of anything about quantum states) is how do they KNOW that it is in 2 states at once? Measuring it and getting different states could just as easily mean that it is at the tipping point between the state changes and isn't actually both states but alternating between the two states as it keeps raising and lowering below that threshold of energy required to be in a given state, maybe in units of energy so small we have not yet learned to detect yet. What am I missing here?
Re:so how big is it? (Score:5, Interesting)
Disproof of Penrose, evidence for MWI (Score:3, Interesting)
If it is true that '"I don't think there is a limit, that there will be a certain size where quantum mechanics starts to break down," Dr Aspelmeyer said,' then that means that even larger objects also go into superpositions of quantum states. That would go all the way up to human sized and larger. This is the fundamental principle of the Many-Worlds Interpretation (MWI), that when quantum measurements occur, even though we only see one outcome, actually we go into a superposition of multiple states, each of which sees a different outcome. Each state evolves independently. It is as though the world splits into parallel universes, where every possible outcome occurs in a different universe.
This follows strictly from the principle that QM applies at all sizes. And this new experiment certainly pushes us in that direction.
Some scientists, notably Roger Penrose, had speculated that QM would break down at macroscopic sizes. He specifically proposed that once sizes were large enough for gravitational forces to exceed some threshold, QM would break down. Wikipedia [wikipedia.org] has this: "Tiny superpositions, e.g. an electron separated from itself, if isolated from environment, would require 10 million years to reach OR threshold. An isolated one kilogram object (e.g. Schrödinger's cat) would reach OR threshold in only 10^-37 seconds." Now here we have a trilliion atom object. That is about 10^13 amu, which is 10^-14 kg. Dividing 10^-37 seconds by 10^-14 we get 10^-23 seconds, which is far shorter than this experiment lasted. This means basically that this experiment disproves Penrose's theory! This is the first time this has happened, and I am (AFAIK) the first person to notice this.
In short it is becoming harder and harder to avoid accepting the reality of parallel worlds. What this should mean for our actions is up to the philosophers, but we should not bury our heads and pretend it isn't true.
Re:so how big is it? (Score:3, Interesting)
From:
http://en.wikipedia.org/wiki/Path_integral_formulation#Feynman.27s_interpretation [wikipedia.org]
"In order to find the overall probability amplitude for a given process, then, one adds up, or integrates, the amplitude of postulate 3 over the space of all possible histories of the system in between the initial and final states, including histories that are absurd by classical standards."
So, for a photon that goes trough one or the other slit, you integrate over both, and you end up with the interference pattern in your calculation. Also, the same photon goes to the end of the universe, splits into a pair of two cars (one car, one anti-car) that merge back to a photon, then it goes back to your detector behind slits. However, this contributes very little to the end result. However you add all those probabilities.
But from photon's perspective, the universe is contracted to the length of zero in the direction it travels, so, it gets there in zero time, as if its starting point and end point are one and the same.
Can somebody smart connect those two views?