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"Spooky" Quantum Entanglement Reveals Invisible Objects
In a physics first, a quantum camera captures images with two-colored light that never "saw" the object.
Like twins separated at birth who are later reunited, two laser beams revealed invisible objects in a display of their weird quantum connection, researchers reported on Wednesday.
The images, of tiny cats and a trident, are an advance for quantum optics, an emerging physics discipline built on surprising interactions among subatomic particles that Einstein famously called "spooky." (Related: "Teleportation: Behind the Science of Quantum Computing.")
A conventional camera captures light that bounces back from an object. But in the experiment reported in the journal Nature, light particles, or photons, that never strike an object are the ones that produce its picture.
"Even other physicists say 'you can't do that' at first, but that is quantum behavior for you, very strange," says Gabriela Barreto Lemos of the Institute for Quantum Optics and Quantum Information in Vienna, Austria, who led the study.
A 2009 University of Glasgow experiment with a divided laser beam first demonstrated such "ghost imaging." But experts say the new technique, which uses two laser beams of different colors, offers new visualization advantages.
The two laser beams are "entangled" in quantum physics terms, meaning their photons share characteristics even when far apart. So broadly speaking, altering one alters the other.
"What they've done is a very clever trick. In some ways it is magical," says quantum optics expert Paul Lett of the National Institute of Standards and Technology in Gaithersburg, Maryland, who was not part of the experiment team. "There is not new physics here, though, but a neat demonstration of physics."
Optics Goes Quantum
The new imaging technique may allow for improved medical imaging or silicon chip lithography in hard-to-see situations, the team suggests.
In medicine, for instance, doctors might probe tissues using invisible wavelengths of light that won't damage cells, while simultaneously using entangled visible light beams to create clear images of the tissues.
"The two-color advantage is a cool idea," Lett says. "It happens a lot in imaging that the best wavelength of light for a probe is not the one that makes for the best picture. You can imagine tuning light colors like this to get the best advantages of both."
In particular, the experiment's approach could create images in visible light of objects that normally can be seen only under infrared light, says quantum optics expert Miles Padgett of Scotland's University of Glasgow, who headed the 2009 "ghost imaging" experiment.
Ironically, the idea of entanglement owes something to Einstein, who in 1935 criticized it as an unlikely (in his view) mathematical shortcoming of quantum physics, which treats subatomic particles as both point-like and as waves.
Manipulating these wavy particles, quantum physics predicted, would alter other seemingly unconnected particles far away. Einstein called this interference (in translation), "spooky action at a distance," which he saw as unlikely. But it turns out to work.
In the new experiment, the physicists entangled photons in two separate laser beams with different wavelengths, and hence color: one yellow and one red. (Watch: "None of the Above: Fun With Laser Beams.")
The team passed the red light beam through etched stencils and into cutouts of tiny cats and a trident, about 0.12 inches (3 millimeters) tall. The yellow beam traveled on a separate line, never hitting the objects. What's more, the etched shapes were designed to be invisible to yellow light.
The cat shape is a nod to physicist Erwin Schrödinger, who invented the famous "Schrödinger's cat" paradox, a thought experiment in which a notional cat is simultaneously dead and alive. Subatomic particles do seem to behave in this peculiar way sometimes, occupying many places at once.
After the red light passed by the objects, the physicists ran it together with the yellow laser beam at both parallel and right angles.
The red light was then discarded, and the yellow light headed for a camera. There, that yellow light revealed a picture of the object. And a negative of the picture emerged from the light that had interfered at a right angle.
"The phenomena really arises from the interference of the photons together," Lemos says. "It's not that the red photons have changed the yellow ones, it's that quantum mechanics says they have to share [wavelength] phases which we can detect to see a picture."
Although the experiment team has applied for a patent, Lemos acknowledges that practical applications may take awhile.
"This is a long-standing, really neat experimental idea," says Lett. "Now we have to see whether or not it will lead to something practical, or will remain just a clever demonstration of quantum mechanics."
originally posted by: VegHead
What a cool experiment - thank you so much for posting (and including the pics!)
Now, I've only had one sip of my morning coffee, so please forgive me... but how is this (in your view) connected to verifying the reality of consciousness? I can't quite make that connection, but I'd like to.
originally posted by: weirdguy
originally posted by: VegHead
What a cool experiment - thank you so much for posting (and including the pics!)
Now, I've only had one sip of my morning coffee, so please forgive me... but how is this (in your view) connected to verifying the reality of consciousness? I can't quite make that connection, but I'd like to.
Creepy street mimes are for real.
The geometry of 4-dimensional space is much more complex than that of 3-dimensional space, due to the extra degree of freedom.
Just as in 3 dimensions there are polyhedra made of two dimensional polygons, in 4 dimensions there are polychora (4-polytopes) made of polyhedra. In 3 dimensions there are 5 regular polyhedra known as the Platonic solids. In 4 dimensions there are 6 convex regular polychora, the analogues of the Platonic solids. Relaxing the conditions for regularity generates a further 58 convex uniform polychora, analogous to the 13 semi-regular Archimedean solids in three dimensions.
A useful application of dimensional analogy in visualizing the fourth dimension is in projection. A projection is a way for representing an n-dimensional object in n − 1 dimensions. For instance, computer screens are two-dimensional, and all the photographs of three-dimensional people, places and things are represented in two dimensions by projecting the objects onto a flat surface. When this is done, depth is removed and replaced with indirect information. The retina of the eye is also a two-dimensional array of receptors but the brain is able to perceive the nature of three-dimensional objects by inference from indirect information (such as shading, foreshortening, binocular vision, etc.). Artists often use perspective to give an illusion of three-dimensional depth to two-dimensional pictures.
Similarly, objects in the fourth dimension can be mathematically projected to the familiar 3 dimensions, where they can be more conveniently examined. In this case, the 'retina' of the four-dimensional eye is a three-dimensional array of receptors. A hypothetical being with such an eye would perceive the nature of four-dimensional objects by inferring four-dimensional depth from indirect information in the three-dimensional images in its retina.
The perspective projection of three-dimensional objects into the retina of the eye introduces artifacts such as foreshortening, which the brain interprets as depth in the third dimension. In the same way, perspective projection from four dimensions produces similar foreshortening effects. By applying dimensional analogy, one may infer four-dimensional "depth" from these effects.
As an illustration of this principle, the following sequence of images compares various views of the 3-dimensional cube with analogous projections of the 4-dimensional tesseract into three-dimensional space.
Are our thoughts made of the distributed kind of electromagnetic field that permeates space and carries the broadcast signal to the TV or radio?
Professor Johnjoe McFadden from the School of Biomedical and Life Sciences at the University of Surrey in the UK believes our conscious mind could be an electromagnetic field.
“The theory solves many previously intractable problems of consciousness and could have profound implications for our concepts of mind, free will, spirituality, the design of artificial intelligence, and even life and death,” he said.
Most people consider "mind" to be all the conscious things that we are aware of. But much, if not most, mental activity goes on without awareness. Actions such as walking, changing gear in your car or peddling a bicycle can become as automatic as breathing.
The biggest puzzle in neuroscience is how the brain activity that we're aware of (consciousness) differs from the brain activity driving all of those unconscious actions.
When we see an object, signals from our retina travel along nerves as waves of electrically charged ions. When they reach the nerve terminus, the signal jumps to the next nerve via chemical neurotransmitters. The receiving nerve decides whether or not it will fire, based on the number of firing votes it receives from its upstream nerves.
In this way, electrical signals are processed in our brain before being transmitted to our body. But where, in all this movement of ions and chemicals, is consciousness? Scientists can find no region or structure in the brain that specializes in conscious thinking. Consciousness remains a mystery.
“Consciousness is what makes us 'human,' Professor McFadden said. “Language, creativity, emotions, spirituality, logical deduction, mental arithmetic, our sense of fairness, truth, ethics, are all inconceivable without consciousness.” But what’s it made of?
One of the fundamental questions of consciousness, known as the binding problem, can be explained by looking at a tree. Most people, when asked how many leaves they see, will answer "thousands." But neurobiology tells us that the information (all the leaves) is dissected and scattered among millions of widely separated neurones.
Scientists are trying to explain where in the brain all those leaves are stuck together to form the conscious impression of a whole tree. How does our brain bind information to generate consciousness?
What Professor McFadden realized was that every time a nerve fires, the electrical activity sends a signal to the brain's electromagnetic (em) field. But unlike solitary nerve signals, information that reaches the brain's em field is automatically bound together with all the other signals in the brain. The brain's em field does the binding that is characteristic of consciousness.
What Professor McFadden and, independently, the New Zealand-based neurobiologist Sue Pockett, have proposed is that the brain's em field is consciousness.
The team passed the red light beam through etched stencils and into cutouts of tiny cats and a trident, about 0.12 inches (3 millimeters) tall. The yellow beam traveled on a separate line, never hitting the objects. What's more, the etched shapes were designed to be invisible to yellow light.
After the red light passed by the objects, the physicists ran it together with the yellow laser beam at both parallel and right angles. The red light was then discarded, and the yellow light headed for a camera. There, that yellow light revealed a picture of the object. And a negative of the picture emerged from the light that had interfered at a right angle.