"Physicists Create New Form of Light"

[Skwim]

Newly observed optical state could enable quantum computing with photons


Try a quick experiment: Take two flashlights into a dark room and shine them so that their light beams cross. Notice anything peculiar? The rather anticlimactic answer is, probably not. That's because the individual photons that make up light do not interact. Instead, they simply pass each other by, like indifferent spirits in the night.

But what if light particles could be made to interact, attracting and repelling each other like atoms in ordinary matter? One tantalizing, albeit sci-fi possibility: light sabers -- beams of light that can pull and push on each other, making for dazzling, epic confrontations. Or, in a more likely scenario, two beams of light could meet and merge into one single, luminous stream.

It may seem like such optical behavior would require bending the rules of physics, but in fact, scientists at MIT, Harvard University, and elsewhere have now demonstrated that photons can indeed be made to interact -- an accomplishment that could open a path toward using photons in quantum computing, if not in light sabers.

In a paper published today in the journal Science, the team, led by Vladan Vuletic, the Lester Wolfe Professor of Physics at MIT, and Professor Mikhail Lukin from Harvard University, reports that it has observed groups of three photons interacting and, in effect, sticking together to form a completely new kind of photonic matter.

In controlled experiments, the researchers found that when they shone a very weak laser beam through a dense cloud of ultracold rubidium atoms, rather than exiting the cloud as single, randomly spaced photons, the photons bound together in pairs or triplets, suggesting some kind of interaction -- in this case, attraction -- taking place among them.
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"Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibers," Vuletic says. "If photons can influence one another, then if you can entangle these photons, and we've done that, you can use them to distribute quantum information in an interesting and useful way."

Going forward, the team will look for ways to coerce other interactions such as repulsion, where photons may scatter off each other like billiard balls.

"It's completely novel in the sense that we don't even know sometimes qualitatively what to expect," Vuletic says. "With repulsion of photons, can they be such that they form a regular pattern, like a crystal of light? Or will something else happen? It's very uncharted territory."
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[BSM1]

Alright. Stupid question of the day. If you shine the flashlights so the beams cross, do the photons at the junction pass through each other, pass around each other, exchange places with each other, or should I be happy that I didn't run a nail through my thumb in shop class?

 

[Polymath257]

Alright. Stupid question of the day. If you shine the flashlights so the beams cross, do the photons at the junction pass through each other, pass around each other, exchange places with each other, or should I be happy that I didn't run a nail through my thumb in shop class?

In the absence of other matter, the closest is to say they 'go through' each other. But even that isn't correct. The probability waves pass through each other in the way that water waves will. The probability waves describe the probability of detecting a photon.

Thinking about photons as little balls is not going to be helpful.

 

[Revoltingest]

Someone has to say it....

 

[The Kilted Heathen]

Screw lightsabers, bring on the hardlight!

 

[BSM1]

In the absence of other matter, the closest is to say they 'go through' each other. But even that isn't correct. The probability waves pass through each other in the way that water waves will. The probability waves describe the probability of detecting a photon.

Thinking about photons as little balls is not going to be helpful.

Okay. So far so good, but can't photons be a wave and a beam at the same time (keeping it simple so I don't hurt anything upstairs).

 

[Twilight Hue]

Newly observed optical state could enable quantum computing with photons


Try a quick experiment: Take two flashlights into a dark room and shine them so that their light beams cross. Notice anything peculiar? The rather anticlimactic answer is, probably not. That's because the individual photons that make up light do not interact. Instead, they simply pass each other by, like indifferent spirits in the night.

But what if light particles could be made to interact, attracting and repelling each other like atoms in ordinary matter? One tantalizing, albeit sci-fi possibility: light sabers -- beams of light that can pull and push on each other, making for dazzling, epic confrontations. Or, in a more likely scenario, two beams of light could meet and merge into one single, luminous stream.

It may seem like such optical behavior would require bending the rules of physics, but in fact, scientists at MIT, Harvard University, and elsewhere have now demonstrated that photons can indeed be made to interact -- an accomplishment that could open a path toward using photons in quantum computing, if not in light sabers.

In a paper published today in the journal Science, the team, led by Vladan Vuletic, the Lester Wolfe Professor of Physics at MIT, and Professor Mikhail Lukin from Harvard University, reports that it has observed groups of three photons interacting and, in effect, sticking together to form a completely new kind of photonic matter.

In controlled experiments, the researchers found that when they shone a very weak laser beam through a dense cloud of ultracold rubidium atoms, rather than exiting the cloud as single, randomly spaced photons, the photons bound together in pairs or triplets, suggesting some kind of interaction -- in this case, attraction -- taking place among them.
.
.
.

"Photons can travel very fast over long distances, and people have been using light to transmit information, such as in optical fibers," Vuletic says. "If photons can influence one another, then if you can entangle these photons, and we've done that, you can use them to distribute quantum information in an interesting and useful way."

Going forward, the team will look for ways to coerce other interactions such as repulsion, where photons may scatter off each other like billiard balls.

"It's completely novel in the sense that we don't even know sometimes qualitatively what to expect," Vuletic says. "With repulsion of photons, can they be such that they form a regular pattern, like a crystal of light? Or will something else happen? It's very uncharted territory."
source and more

.​

Didn't Ghostbusters say to never cross the beams?

 

[Polymath257]

Okay. So far so good, but can't photons be a wave and a beam at the same time (keeping it simple so I don't hurt anything upstairs).

Well, *all* quantum 'particles' have both wave and particle aspects. The wave aspect determines the probability of detecting the corresponding particle. The question is to what extent two different waves move through each other without affecting each other. For light, there is generally no interaction.

In the OP case, two photons of light interact with an atom and thereby with each other through the effects on the atom. That is enough to 'bind' the photons together even after they move past the atom. The experiment went even farther, though, and bound three photons together using this trick.

Cool stuff!