Rules of Physics in Quantum World Change When Applied to Classical World

From ScienceDaily:

In a study published in the July 1 issue of the journal Nature, Associate Professor of Physics and Astronomy Alex Rimberg and his colleagues describe one example of the microscopic quantum world influencing, even dominating they say, the behavior of something in the macroscopic classical world.

They used tiny semiconducting crystals that contain two separate reservoirs of electrons to explore the different influences of both classical and quantum physics.

“We found that the motion of the crystals is not dominated by something classical like thermal motion, but instead by random quantum fluctuations in the number of electrons tunneling through the barrier; the fluctuations were the size of about 10,000 electrons,” says Rimberg. “But the macroscopic world in this study also influences the quantum world, in that the vibrations of the crystal caused the electrons to tunnel in big bunches, more or less in sync with the vibrations of the crystal.”

I’ve blogged about this sort of thing before. It’s an artificial division that quantum mechanics applies to the world of the very tiny, and classical mechanics applies to the macro world. There’s a transition where the classical mechanics we developed becomes a pretty good approximation, but it’s probably a smooth (if quick) transition. We’re going to continue to find overlaps like this, and quantum effects will continue to wreak their weird (to us) havoc on the world we think we know.

Quantum mechanics: context does matter

I’ve blathered on about quantum mechanics enough to make clear – if it wasn’t already – that it’s deeply non-intuitive stuff.

One way that some thinkers (including Einstein) try to get around the apparently statistical (they felt, random) nature of quantum behaviour is viahidden variables. This theory is that there are other factors, or laws, or powers, or effects at play that we simply haven’t discovered yet. If we did, we’d see that quantum mechanics is actually deterministic, not statistical or determined by things like whether we’re observing behaviour or not, and would fit more comfortably into the way we think the world works.

This has always seemed like wishful thinking to me.

Now some scientists at the Austrian Institute of Quantum Optics and Quantum Information (I blogged about their experiments in larger-scale entanglementin June) have shown that quantum behavior cannot be explained away by non-contextual models of hidden variables. The freaky behaviour stays.

Read more about it at ScienceDaily or in the current issue of Nature.

Scientists create first electronic quantum processor

From breaking science news site Eurekalert:

A team led by Yale University researchers has created the first rudimentary solid-state quantum processor, taking another step toward the ultimate dream of building a quantum computer.

They also used the two-qubit superconducting chip to successfully run elementary algorithms, such as a simple search, demonstrating quantum information processing with a solid-state device for the first time. Their findings will appear in Nature‘s advanced online publication June 28.

“…This is the first time they’ve been possible in an all-electronic device that looks and feels much more like a regular microprocessor.”

The key that made the two-qubit processor possible was getting the qubits to switch “on” and “off” abruptly, so that they exchanged information quickly and only when the researchers wanted them to.

The article is a good read. Get your head around their example of how quantum computation might be different from the kind of computation we’re used to:

Imagine having four phone numbers, including one for a friend, but not knowing which number belonged to that friend. You would typically have to try two to three numbers before you dialed the right one. A quantum processor, on the other hand, can find the right number in only one try.

Entanglement even spookier

Entanglement is a quantum mechanics phenomenon. It’s been called “spooky action at a distance” because we can see that – on tiny scales at least – particles that were once together seem to have an instant effect on each other even when separated by vast distances. Take two electrons, move them apart, change one of them a little bit, and the other one seems to change correspondingly and instantly.

We don’t yet know why or how quantum entanglement happens. It’s also not clear why we don’t seem to see the effects on the everyday scale of the universe we can directly observe. But entanglement is a solid, proven, never-failing fact. Until recently, however, it’s only been seen in things like the spin of electrons, or the polarisation of photons.

A few years ago the Institute for Quantum Optics and Quantum Information in Austria did some tests – now being published in Nature – that demonstrate entanglement at the atomic level. This is a step up the mechanical chain, a level closer – though still pretty far from – the apparently classical world we’re familiar with.

I think it’ll be really interesting to discover at what point on the subatomic-to-breadbox scale that these quantum entanglement effects disappear (if they really do at all).

Quantum mechanics: maybe there are no “many worlds”, maybe it’s decoherence

There’s a nifty quantum mechanics bitchfight difference of opinion going on at Uncertain Principles. Read the comments.

This decoherence approach is not one that I’d reach about before, but I like it. I must admit that the “many worlds” notion always seemed to me more like a comfortable notion that we could get our heads around rather than a genuine interpretation about what might be happening.