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Quantum Limit of Gadgets Found? DNews Nugget

Quantum Jitters: Yesterday, I visited my local Apple store to fix an iPhone glitch. It turns out that hanging around for too long in Apple stores is a very bad idea -- I was a heartbeat away from handing over my credit card to buy a shiny new iMac. As I played with the touchpad on one of Apple's beautiful machines, swiping through screens like Tom Cruise in Minority Report, I started to ponder: How will it all end? After all, miniaturization can only go so far, but what's the limit? Well, it turns out that researchers might have found it.

Moore's Law dictates that every 18 months, the density of transistors on integrated circuits should double. This is a basic tenet of technology and is the driving miniaturization factor that gives us computers that can fit in our pockets. However, according to researchers at McGill University and General Motors who carried out tests on a microscopic tungsten probe and gold surface interface, when they applied electricity across the interface, the current dropped off far quicker than they predicted. Basically, they had probed the quantum limit of the flow of electrons through the material.

"You could use the analogy of a water hose," said Peter Grütter, a physics professor at McGill University. "If you keep the water pressure constant, less water comes out as you reduce the diameter of the hose. But if you were to shrink the hose to the size of a straw just two or three atoms in diameter, the outflow would no longer decline at a rate proportional to the hose cross-sectional area; it would vary in a quantized ('jumpy') way."

So if you make your components too thin, rather than having a flow of current, you will eventually see quantum effects that could make gadgets problematic to design. via Futurity.com

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Quantum Computing Closer with Lasers

In the future, computers will be faster than the fastest supercomputers of today, they'll be able crack any code, analyze gobs of data and know immediately if they're being infiltrated by hackers. The computers able to do that will be based on quantum physics, a mysterious and paradoxical area of physics that scientists are still trying to figure out. It requires, at its foundation, the ability to control a single photon.

But now, an international team of physicists and computer scientists from the Massachusetts Institute of Technology and led by Thibault Peyronel has built a device that turns a laser beam into a stream of single photons that can be turned on and off. That capability could lead to a quantum transistor. Transistors in conventional computers are turned on and off by electrical current.

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"What you have is individual photons controlling the switch," Thad Walker, professor of physics at the University of Wisconsin, told Discovery News. Walker was not connected with the research.

To get single photons, Peyronel and the team used two laser beams. The first one they at a cloud of rubidium atoms that were chilled to a temperature that was just hair above absolute zero. Next, the fired a second laser beam, called a control beam.

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Ordinarily, rubidium atoms are opaque. But after being hit with the second laser beam, they became transparent. In that state, photons were able to pass through the atoms, albeit slowly.

The photon didn't just slow down, either. Because the the rubidium atoms were in such an excited state, only one photon at a time was able to pass through the atom. When another photon entered the cloud of atoms, the rubidium becames opaque and the photon was unable to pass through.

Turning off the control beam also rendered the rubidium atom opaque, blocking any photons from passing through. That means the apparatus is an optically controlled switch, one that works on single photons.

The effect also implies that one could build a kind of quantum transistor. A rubidium chamber emitting single photons could be placed next to another just like it. The single photons would go to the second chamber. The first ones to get there could be let through while later ones would be stopped. Turn off the first chamber for a moment and the second one "opens" again.

That is essentially how transistors in conventional computers work, only those are controlled by electric current.

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The ability to send single photons also means it's possible to build a true quantum communications system. Quantum communications can't be eavesdropped upon, because doing so alters the state of the bits being transmitted. That's a dead giveaway to the person receiving the transmission.

This isn't the only group that managed to control single photons. At Georgia Tech, Alex Kuzmich and Yaroslav Dudin used a similar technique to produce single-photon emissions.

Walker noted these experiments also open the way to a lot of fundamental physics research. Ordinarily when a quantum state is measured, the photon is destroyed. The ability to control the transmission of one photon at a time also means one can measure the quantum state of the incoming photon without actually "touching" it.

The MIT research appeared in the journal Nature on July 25.

Image: MIT / Ofer Firstenberg and Yoav Sterman.

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A Baby Quantum Internet Was Born Today

Years from now it may be said that the quantum Internet was born today. When the baby system matures, it will be able to process unfathomable amounts of data and never be hacked.

The system only has two nodes, but the Internet's birth started in a similar way back in the late 1960s. The developers -- physicists led by Stephan Ritter and Gerhard Rempe of the Max Planck Institute of Quantum Optics in Germany -- published their work in this week's issue of the journal "Nature."

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The quantum network was built using two atoms of rubidium that exchange photons, or particles of light. Each atom is placed inside a cavity with highly reflecting mirrors on each side, and at a very short distance from each other. The two so-called optical cavities are connected by an optical fiber.

Scientists aim a laser at the first atom, causing the atom to emit a single photon. That photon zooms along the optical fiber to other optical cavity containing the other atom. That's where the mirrors come in -- ordinarily it's difficult to get an atom and a photon to interact reliably. But by bouncing the photon off the mirrors in the cavity thousands of times, it's more likley to hit the atom and be absorbed by it. That absorbtion is what transmits the information about the first atom's quantum state to the second atom.

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Besides sending information, the two atoms were entangled, meaning that the atoms were linked. If the first node is in quantum state A, for example, the second node will also be in quantum state A. In this experiment, the atoms were entangled for 100 microseconds -- a long time in quantum physics.

This entanglement is what makes hacking into a quantum computer and eavesdropping on impossible. As as soon as a hacker tapped into a quantum network, the states of the atoms wouldn't match up -- a big red flag that something was awary.

It's a long way yet to a truly large-scale quantum network, but this is a first step.

via Max Planck Institute for Quantum Optics

Image: Andreas Neuzner, Max Planck Institute for Quantum Optics

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Disc Levitates With Amazing Quantum Trapping

What you're seeing is called quantum trapping.

As little pieces of science fiction start to slip into every day society, it's becoming harder to get us excited about new technologies. This is not one of those times. This preliminary research by physicists at Tel Aviv University will make your jaw drop. It shows quantum trapping technology that resembles magic.

Quantum trapping uses a stable magnetic field to "clamp" this super-frozen, super-thin disc in three-dimensional space. With the stability of quantum trapping, the disc will hang in space even when the whole apparatus is inverted. Quantum mechanics deals with the motion and interaction of matter on the subatomic level, which means physics concerning particles smaller than the individual atoms that make up matter.

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In the video is a single crystal layer of crystal sapphire, paired with a ceramic layer. The super thin layers are then cooled to -301 Fahrenheit (-185 Celcius). At these frigid temperatures, the ceramic becomes a superconductor and conducts electricity with no resistance at all.

In addition to electricity, the disc also experiences the Meissner effect. Hang on, it's not that difficult. This Meissner effect explains the magnetic properties of superconductors. Normally, a magnetic field would pass through a disc, attracting or repelling all parts at the same time. But when the disc is a superconductor, the magnetic field travels around the disc and only forces itself through the weakest points. It's at these points where quantum mechanics takes over. The disc becomes trapped in space, a concept aptly named quantum trapping.

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It might look like magic, but it's just quantum mechanics. Someday, technology like this could change how we transport materials, or ourselves! What if cars floated off the ground? What about hoverboards? We'll have to wait and see what this can do for science. Leave a comment with your idea for quantum trapping!

Photo: www.QuantumLevitation.com

Let Quantum Physics Officiate Your Wedding

For the ultimate in a nondenominational wedding ceremony, consider a quantum entanglement. The ceremony, developed by conceptual artist, Jonathon Keats, is borrowed from quantum physics, where when two or more subatomic particles become entangled, they behave as one.

Keats has designed an entangling apparatus, which, when situated in a sunny window and exposed to the full spectrum of solar radiation divides pairs of entangled photons and translates them to the bodies of a nearby couple.

A scenario might go like this, said Keats in an email correspondence with Discovery News about his project:

In the simplest case, involving only two people, the couple begins by walking down a long hallway from darkness into sunlight. (The hallway is wide enough for them to walk side by side, but too narrow to accommodate more than two people at a time.) At the end of the hallway, the couple will find two sets of footprints, on which they'll stand facing one another, nearly touching. (Depending on their preference, they may be dressed or naked.) They'll look up and see a window bright with sunlight, and suspended in that window above their heads they'll find the entanglement apparatus, which has been precisely calibrated (using a system of adjustable prisms) to divide the sunlight passing through a nonlinear crystal (made of beta-barium borate) so that half of the light shines on each person's face. They'll stand for approximately a minute, allowing countless entangled photons to bombard their skin, gently entangling their flesh by the photoelectric effect. Then they'll turn away and walk back down the hall and out into the open.

According to Keats, the couple won't know to what extent they've become entangled, because any attempt to measure a quantum system disturbs it.

"The quantum marriage will literally be broken up by skepticism about it," he said. 

Basically they have to take it on faith.

Entanglements will be available from May 12 to June 18 2011 in the South Alcove of the AC Institute, 547 W. 27th St, 6th Floor, in New York City.

Credit: Jonathon Keats

 

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