In that way it is also possible to photograph pictures in wavelength ranges for which one has no detectors at all.

Entanglement and photography - Comment on 2014 August 29

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One can photograph an object by illuminating it with light, which reaches from ultraviolett via the infrared perhaps even up to tera Hertz radiation, while the picture is recorded with a freely chosen wave length, for which there are efficient detectors. Read more:

Today I bring extracts from several reports about a scientific announcement.

The reports contain interesting material about two subjects, which touch the spiritual side of science: entanglement and light.

One of the results of this experiment is that ways now exist to photograph pictures in wavelength ranges for which one has no detectors at all.

This seems to indicate that we might have cameras in future with which we can take pictures of things normally not visible to the human eye.

For example is ultraviolet radiation no longer perceived by the human eye; many animals, like insects, birds, fish, reptiles, can however partly see it. We could therefore have a camera which shows pictures of that what a certain bird sees. Or we could have a camera which sees what a person sees, who claims to see a spirit, a ghost, or who sees what a seer sees. We could therefore take a picture of what is in the spiritual kingdom, perhaps the soul of a deceased person, for example of an earthbound spirit.

Now the extracts:


Quantum imaging without light of the original picture

A photo of an object is based on the radiation, which comes from it. Intuitively observed light cannot contain information about an object, with which it never had interaction. Scientist around Gabriela Barreto Lemos of the institute for quantum optics and quantum information in Vienna now succeeded however in photographing a subject through light particles, which never had contact with the object. This method based on quantum states the scientists now introduced in the special journal "Nature".

In allusion to Schrödinger’s famous thought experiment the scientist took a photograph of the silhouette of a cat, which they had cut out of a cardboard. For that purpose the researchers separated quantum mechanically entangled pairs of photons into two rays. In each case they led one of the partners through the pattern, the other past it. Two entangled objects form at it were a unit and can only be described together: When the state of one is changed, this also becomes apparent in the state of the other – no matter how far away both are from each other. In the experiment arrangement the scientists redirected the rays several times and superimposed them with each other. Finally the picture resulted out of a detector signal, to which only those partners contributed, which never interacted with the object. But through the entanglement also these light particles received information about the original pictures. In a strongly simplified description Barreto Lemos and her colleagues used the one partner of the entangled state for gathering, the other for the writing of the object information.

The scientists consciously produced the two entangled photons with different wave lengths to demonstrate the suitability of application of their method. So the cardboard material let the registered photons pass unhindered, while the detector was not sensitive to such photons, with which the pattern interacted. When an object only sends out difficult measurable rays, as it is for example the case with natural luminescences of certain organisms, then a picture could still be taken with this method: by means of better measurable partner photons.


Schrödinger's cat caught on quantum film

Schrödinger's cat is the poster child for quantum weirdness. Now it has been immortalised in a portrait created by one of the theory's strangest consequences: quantum entanglement.

These images were generated using a cat stencil and entangled photons. The really spooky part is that the photons used to generate the image never interacted with the stencil, while the photons that illuminated the stencil were never seen by the camera.

When two separate particles are entangled, measurements of their physical properties are correlated, and they effectively share a single quantum state. Gabriela Barreto Lemos at the Austrian Academy of Sciences in Vienna and her colleagues used this quantum connection between particles to make these images of a cat without directly photographing it.

To do it, the researchers created yellow and red pairs of entangled photons. The yellow photons were fired at the cat stencil, while the red photons were sent to the camera. Thanks to their entanglement, the red photons formed the image of the cat because of the quantum link to their yellow twins.

The silicon stencil was transparent to red light and the camera could only detect red light. This demonstrates that the technique can image objects that are invisible to the detected photons.


"We illuminate an object with infrared photons, which we do not register at all. Then we produce the picture with red photons, which were never near the object", explains the Brazilian physicist Gabriela Barreto Lemos, who at present is post graduate student studying for a doctorate at Zeilinger’s institute.

How can that work? With entanglement, which is a speciality of the quantum world. Entangled particles – for example light particles, photons – are connected with each other, without that information must be transmitted over space. Such pairs of entangle photons come into being when laser light hits upon a certain kind of crystals (not linear crystals).

Barreto Lemos and her colleagues produced from a green ray of light in two crystals such entangled pairs out of photons with different wave length: in each case one red and the other infrared. Then they placed the object to be photographed – a diaphragm with the outline of a cat – between two crystals, and that is so that only the infrared photons out of the first crystal went through the object. They hit upon the infrared photons out of the second crystal, and that is so that one could no longer differentiate afterwards from where the infrared photons had come that therefore no longer information about the object were contain in them.

Exactly through this the information about the object was now only all in the red photons – although they had never touched the object. And so out of the interference of the two red rays – one out of the first crystal, one out of the second – the picture of the object could come into being: the silhouette of the cat, once as positive, once as negative. The infrared photons, which were very well in interaction with the object, did not have to be registered. That would also not have been easy: At the moment there are no sufficient efficient infrared cameras.

A practical meaning of this experiment could lie in this: "One can photograph an object by illuminating it with ultraviolet or infrared light, while recording the picture with a free chosen wave length for which there are efficient detectors", says Anton Zeilinger. That one could for example use for picture giving processes in medicine. So Barreto Lemos and her colleagues have already applied for a patent on their process.


Quantum entanglement camera images object with photons that never come near it

Researchers used a quantum entanglement camera to image a cat etched on a piece of silicon. Photons that interact with the silicon are not used to form the image directly. The photons are entangled to other photons in a different wavelength, and these are detected to form the image instead. In other words, the image is obtained by detecting only photons that never interact with the silicon. There are two images (dark and light cat) because the camera relies on destructive and constructive quantum interference, producing both a positive and negative image.

Conventional imaging devices like cameras and x-ray machines create pictures by detecting photons that interact with the things being imaged. Now researchers have developed a new quantum imaging technique that shines a beam of photons on an object but then, instead of using these photons to form a picture, uses instead a completely different beam that has never come near the object. If this sounds a bit spooky, it is: what connects the two sets of photons and allows this technique to work is the bizarre quantum physics phenomenon known as entanglement.

The advantage of a quantum entanglement camera like this is that you can illuminate an object using photons with a certain wavelength and then use entangled photons with a different wavelength to form the image. The scientists have already begun investigating possible biotechnological applications such as capturing images of sensitive samples that would be destroyed by conventional imaging techniques.

Entanglement is a fundamentally quantum mechanical relationship between two particles - in this case, photons - created in a kind of extreme, nonlinear crystal that can split individual photons into twin photons. The twin photons behave like distinct and separate photons but also share a separated-at-birth synchronicity unique to the submicroscopic quantum world.

Observation of the first twin photon’s polarization instantaneously forces the second photon into a parallel (or, depending on the setup, perpendicular) polarization state. The paradoxical quality of quantum entanglement, recognized in the 2012 Physics Nobel Prize, is still a mind-bending frontier of fundamental physics. But entanglement’s technological applications, from quantum cryptography to quantum computing, are becoming a reality.

The current research, published in this week’s issue of the journal Nature, harnesses a recently discovered quantum interferometer setup that can effectively create a pair of entangled photons that don't exist at the same time. These photons find themselves in an existential cage match in which only one will survive. The observation of one photon, via this new kind of "time entanglement," necessarily destroys the other.

Gabriela Barreto Lemos is a postdoctoral researcher in the lab of prominent quantum researcher Anton Zeilinger at the Vienna Center for Quantum Science and Technology, in Austria. Barreto Lemos, Zeilinger, and four other researchers turned the above quantum interferometer into a kind of remote-viewing quantum camera, one whose pixels are generated by photons that never come into contact with the object being imaged.

In their experiment, green laser light is twice split into entangled infrared twins, one of which is in the short-wave infrared (SWIR), the other of which is in the near infrared (NIR). One of the SWIR photons then illuminates the object being imaged. Both SWIR photons are ultimately discarded, never to be observed.

But their NIR twins are the ones in the existential cage match: If the imaged object blocks its corresponding SWIR counterpart, then the NIR counterpart gets to exist. It ultimately appears as a pixel on the quantum camera’s image. If SWIR passed through the object, its NIR twin doesn’t exist. Its absence is recorded by the camera as a dark spot.

The end-result is that NIR photons create the image, although no NIR photons illuminated the object. And SWIR photons exclusively illuminated the object, although no SWIR photons are ever detected or observed.

One application of the quantum entanglement camera, Barreto Lemos says, is that the light that illuminates an object can be completely separate from the light that forms the image in the camera.

For instance, imaging some kinds of biological samples with mid-infrared light can be both revealing and valuable. But low-light mid-infrared cameras are also expensive and sometimes unreliable. By contrast, low-light near-infrared cameras ("night vision") are cheap and more robust - and even found in many consumer cameras and camcorders today.

"You could have this [experiment] at visible and mid-infrared wavelengths,"¯ Barreto Lemos says. "The combination of wavelengths is very flexible."


Quantum physics enables revolutionary imaging method

For the first time, an image has been obtained without ever detecting the light that was used to illuminate the imaged object, while the light revealing the image never touches the imaged object.

In general, to obtain an image of an object one has to illuminate it with a light beam and use a camera to sense the light that is either scattered or transmitted through that object. The type of light used to shine onto the object depends on the properties that one would like to image. Unfortunately, in many practical situations the ideal type of light for the illumination of the object is one for which cameras do not exist.

The experiment published in Nature this week for the first time breaks this seemingly self-evident limitation. The object (e.g. the contour of a cat) is illuminated with light that remains undetected. Moreover, the light that forms an image of the cat on the camera never interacts with it. In order to realise their experiment, the scientists use so-called "entangled" pairs of photons. These pairs of photons – which are like interlinked twins - are created when a laser interacts with a non-linear crystal. In the experiment, the laser illuminates two separate crystals, creating one pair of twin photons (consisting of one infrared photon and a "sister" red photon) in either crystal. The object is placed in between the two crystals. The arrangement is such that if a photon pair is created in the first crystal, only the infrared photon passes through the imaged object. Its path then goes through the second crystal where it fully combines with any infrared photons that would be created there.

With this crucial step, there is now, in principle, no possibility to find out which crystal actually created the photon pair. Moreover, there is now no information in the infrared photon about the object. However, due to the quantum correlations of the entangled pairs the information about the object is now contained in the red photons – although they never touched the object. Bringing together both paths of the red photons (from the first and the second crystal) creates bright and dark patterns, which form the exact image of the object.

Stunningly, all of the infrared photons (the only light that illuminated the object) are discarded; the picture is obtained by only detecting the red photons that never interacted with the object. The camera used in the experiment is even blind to the infrared photons that have interacted with the object. In fact, very low light infrared cameras are essentially unavailable on the commercial market. The researchers are confident that their new imaging concept is very versatile and could even enable imaging in the important mid-infrared region. It could find applications where low light imaging is crucial, in fields such as biological or medical imaging.


"Spooky" quantum entanglement reveals invisible objects

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.


Quantum imaging without light of the original picture

In strongly simplified representation Barreto Lemos and her colleagues employed the one partner of the entangled state for collecting, the other for writing of the object information.


Quantum physics enables revolutionary imaging process

Entangled photons depict an object without coming in its nearness

The infrared and the red photons form quantum mechanically entangled pairs, which closely coordinate their behaviour. The researchers produced these pairs of photons by illuminating an optically none-linear crystal with green laser light. Pairs of photons were able to come into being in the crystal out of the green laser light, in each case a red and an infrared light quant. These quants were then separated with a special mirror so that only the infrared photons were directed onto the object, which was to be imaged. After they had passed them not only the infrared but also the photons, which were entangled with them, received the optical information about the object.

"The experiment underlines the fundamental role, which information plays in quantum physics", emphasizes Anton Zeilinger. Moreover the new imaging process opens varied application possibilities. "One can photograph an object by illuminating it with light, which reaches from ultraviolett via the infrared perhaps even up to tera Hertz radiation, while the picture is recorded with a freely chosen wave length, for which there are efficient detectors", explained Zeilinger. That one could for example utilize for the imaging in medicine and for environmental investigations.

Gabriela Barreto Lemos added: "One can irradiate biological samples or semiconductor structures from silicon with light of a certain wave length, which is especially suitable for the imaging. The picture is then produced with light of another wave length, which is coordinated with the detectors." In that way it is also possible to photograph pictures in wavelength ranges for which one has no detectors at all. In the meantime Gabriela Barreto Lemos and her colleagues have applied for a patent for her process, which they want to develop further.


Entangled photons make a picture from a paradox

Quantum imaging outlines objects with light that does not interact with them.

Physicists have devised a way to take pictures using light that has not interacted with the object being photographed.

This form of imaging uses pairs of photons, twins that are ‘entangled’ in such a way that the quantum state of one is inextricably linked to the other. While one photon has the potential to travel through the subject of a photo and then be lost, the other goes to a detector but nonetheless 'knows' about its twin’s life and can be used to build up an image.

Normally, you have to collect particles that come from the object to image it, says Anton Zeilinger, a physicist at the Austrian Academy of Sciences in Vienna who led the work. “Now, for the first time, you don’t have to do that."

One advantage of the technique is that the two photons need not be of the same energy, Zeilinger says, meaning that the light that touches the object can be of a different colour than the light that is detected. For example, a quantum imager could probe delicate biological samples by sending low-energy photons through them while building up the image using visible-range photons and a conventional camera. The work is published in the 28 August issue of Nature.


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