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Monday, June 7, 2010

Jne 3 - How to See Quantum Entanglement‏

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Be Well.

How to See Quantum Entanglement

Human eyes can detect the spooky phenomenon of quantum entanglement — but only sometimes, a new study on the physics preprint website claims. While eyes can help determine if two individual photons were recently entangled, they can’t tell if the brighter bunch of photons that actually hit the retina are in this bizarre quantum state.

“In general you think these quantum phenomena that involve only a few particles, they’re really far removed from us. That is actually not so true anymore,” said physicist Nicolas Brunner of the University of Bristol. “You could really go to an experiment by just having people look at these photons, and from there really actually see entanglement.”

In an earlier paper, Brunner and colleagues at the University of Geneva in Switzerland sketched out an experiment in which a human observer could replace a standard quantum detector. This isn’t as far-fetched as it sounds, they say, because the eye’s most important job is to be a sensitive photon detector.

The researchers would first prepare two entangled photons — photons whose quantum properties are so intimately linked that one always knows what the other is doing. When an aspect of one photon’s quantum state is measured, the other photon changes in response, even when the two photons are separated by large distances.

The researchers would send one photon to a standard detector and the other to a human observer in a dark room. The human would see a dim point of light in either the right or left field of view, depending on the photon’s quantum state. If those flashes of light correlate strongly enough with the output of the ordinary photon detector, then the scientists can conclude that the photons are entangled.

“This is a standard way of measuring and detecting entanglement,” says physicist Nicolas Gisin of the University of Geneva, a coauthor of the new paper.

There’s just one problem: Humans can’t see individual photons. The retina needs at least seven photons to hit it at once before it sends signals to the brain. Also, 90 percent of photons are lost or scattered on the way through the gelatinous part of the eye to the retina. These restrictions mean that you need a lot of photons — at least hundreds, preferably thousands — to make a practical human quantum detector.
In 2008 a group in Rome found a way to clone an entangled photon that preserves the entanglement. If you treat the big bunch of clones as a single quantum state, the entire bunch is entangled with the other original photon, the researchers claimed.

“It’s like having a Schrodinger’s cat,” says Brunner, referring to Erwin Schrodinger’s famous 1935 thought experiment in which a cat in a box has a 50-50 chance of living or dying depending on whether a radioactive atom decays. In this case, the microscopic state of the atom is entangled with the macroscopic state of the cat: Either the atom decays and the cat is dead, or the atom doesn’t decay and the cat is alive. Until someone opens the box, the only way to describe the system is by including both the atom and the cat.

Gisin and colleagues thought this photon-cloning method would be perfect for their human quantum-detector experiments. All they would have to do is make a few thousand copies of one member of the original entangled photon pair, and send all those copies to the human observer.

But because entanglement is easy to break, the team was unsure if the photons that reach the observer’s eyes would still be entangled with the other photon.

To test this idea, Gisin and colleagues imagined what would happen if instead of cloning the original photon, they made the equivalent of a photocopy. Like a black-and-white Xerox of a color picture, some information about the original photon would be lost. Because the copied photons were never entangled with the original, they would still not be entangled when they reached the observer’s eyes.

The researchers compared the theoretical results using photocopied photons and a real quantum cloner, and found that they looked exactly the same. The human observer would see the same thing, even when the bunch of photons were just Xeroxes that couldn’t possibly be entangled with the other photon.

The group concluded that human eyes can’t see quantum entanglement between a macro-state and a micro-state. Schrodinger’s cat may well be entangled with the atom, but a human detector can’t tell.

But the human eye can reliably tell whether the original two photons were entangled. That’s still “seeing” entanglement, the authors say.

“Macro-micro is almost out of the question. But the micro-micro is nice as well,” said study coauthor Christoph Simon of the University of Calgary in Canada. “You’re bringing the observer a little bit closer to the quantum physics.”

The researchers are now working on ways to perform the experiment in the lab and expect it to be ready within two years.

“The theoretical paper is certainly sound and of good quality,” comments physicist Dirk Bouwmeester of the University of California, Santa Barbara.

But Gisin acknowledges that replacing quantum detectors with eyeballs would not lead to any new applications.

“Why do we do it nevertheless?” he says. “We find entanglement fascinating.”

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How to Digitally Record/Video a UFO sighting:

Como registar digitalmente ou gravar um vídeo de um avistamento de um UFO:

Stabilize the camera on a tripod. If there is no tripod, then set it on top of a stable, flat surface. If that is not possible lean against a wall to stabilize your body and prevent the camera from filming in a shaky, unsteady manner.

Estabilize a camera com um tripé. Se não tiver um tripé, então coloque-a em cima de uma superfície estável. Se não for possível, então encoste-se a uma parede para estabilizar o corpo e evitar que a camera registe de maneira tremida e instável.

Provide visual reference points for comparison. This includes the horizon, treetops, lampposts, houses, and geographical landmarks (i.e., Horsetooth Reservoir, Mt. Adams, etc.) Provide this in the video whenever is appropriate and doesn’t detract from what your focus is, the UFO.

Forneça pontos visuais de referência para comparação. Isso inclui o horizonte, cimo das árvores, postes de iluminação, pontos de referência geográficos (como o Reservatório de Horsetooth, Mone Adams, etc) Forneça esses pontos no vídeo sempre que for apropriado e não se distraia do que é o seu foco, o UFO/a Nave.

Narrate your videotape. Provide details of the date, time, location, and direction (N,S,E,W) you are looking in. Provide your observations on the weather, including approximate temperature, windspeed, any visible cloud cover or noticeable weather anomalies or events. Narrate on the shape, size, color, movements, approximate altitude of the UFO, etc and what it appears to be doing. Also include any unusual physical, psychological or emotional sensations you might have. Narrate any visual reference points on camera so they correlate with what the viewer will see, and thereby will be better able to understand.

Faça a narração do vídeo. Forneça pormenores sobre a data, hora, local e direcção (Norte, Sul, Este, Oeste) que está a observar. Faça observações sobre as condições atmosféricas, incluindo a temperatura aproximada, velocidade do vento, quantidade de nuvens, anomalias ou acontecimentos meteorológicos evidentes. Descreva a forma, o tamanho, a cor, os movimentos, a altitude aproximada onde se encontra o UFO/nave, etc e o que aparenta estar a fazer. Inclua também quaisquer aspectos pouco habituais de sensações físicas, psicológicas ou emocionais que possa ter. Faça a narração de todos os pontos de referência visual que o espectador irá ver e que, deste modo, será capaz de compreender melhor.

Be persistent and consistent. Return to the scene to videotape and record at this same location. If you have been successful once, the UFO sightings may be occurring in this region regularly, perhaps for specific reasons unknown, and you may be successful again. You may also wish to return to the same location at a different time of day (daylight hours) for better orientation and reference. Film just a minute or two under “normal” circumstances for comparison. Write down what you remember immediately after. As soon as you are done recording the experience/event, immediately write down your impressions, memories, thoughts, emotions, etc. so it is on the record in writing. If there were other witnesses, have them independently record their own impressions, thoughts, etc. Include in this exercise any drawings, sketches, or diagrams. Make sure you date and sign your documentation.

Seja persistente e não contraditório. Volte ao local da cena e registe o mesmo local. Se foi bem sucedido uma vez, pode ser que nessa região ocorram avistamentos de UFOs/naves com regularidade, talvez por razões específicas desconhecidas, e talvez possa ser novamente bem sucedido. Pode também desejar voltar ao mesmo lugar a horas diferentes do dia (durante as horas de luz)para ter uma orientação e referência melhor. Filme apenas um ,inuto ou dois em circunstâncias “normais” para ter um termo de comparação. Escreva tudo o que viu imediatamente após o acontecimento. Logo após ter feito o registo da experiência/acontecimento, escreva imediatamente as impressões, memórias, pensamentos, emoções, etc para que fiquem registadas por escrito. Se houver outras testemunhas, peça-lhes para registar independentemente as suas próprias impressões, pensamentos, etc. Inclua quaisquer desenhos, esbolos, diagramas. Certifique-se que data e assina o seu documento/testemunho.

Always be prepared. Have a digital camera or better yet a video camera with you, charged and ready to go, at all times. Make sure you know how to use your camera (and your cell phone video/photo camera) quickly and properly. These events can occur suddenly, unexpectedly, and often quite randomly, so you will need to be prepared.

Esteja sempre preparado, Tenha sempre uma camera digital, melhor ainda, uma camera vídeo consigo, carregada e pronta a usar sempre que necessário. Certifique-se que sabe como lidar com a sua camera (ou com o seu celular/camera fotográfica) rápida e adequadamente. Esses acontecimentos podem acontecer súbita e inesperadamente e, por vezes, acidentalmente, por isso, necessita estar preparado.

Look up. Be prepared. Report. Share.

Olhe para cima, Esteja preparado, Relate, Partilhe.



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