All posts by admin

Gravity is capable of causing decoherence of large quantum systems

Fig. 1. A complex molecule in quantum delocalized states simultaneously at two different heights, differing by Δx. Due to the fact that in a gravitational field, time flows differently at different altitudes, the frequency of internal vibrations are slightly different, and this becomes a new source of decoherence of the quantum state. The image of the article under discussion in Nature Physics

In the journal Nature Physics recently published a theoretical article reveals new aspects of the interaction of gravity and quantum mechanics. It shows that in the quantum system of a large number of particles, even if completely isolated from the external environment, but in a gravitational field, it is still going to happen decoherence due to the effect of gravitational time dilation. Although this mechanism does not apply to objects around us, it reveals new details of the transition from the quantum description of large systems to classical.

The transition from quantum to classical – one of the most difficult outstanding issues of fundamental physics. On the one hand, the microscopic world living under the laws of quantum mechanics, with all its counterintuitive phenomena. On the other hand, in the conventional macroscopic physics of these phenomena, we do not see – and, indeed, for this reason, they seem to us unnatural. Most importantly, in the framework of the quantum mechanics do not have any indication of the limits of its applicability of the macroscopic. She says that’s up to the limit of the quantum laws operate, and for him it is necessary to use only the classical physics. Therefore, any transition to classical mechanics must somehow be output directly from the quantum laws, or – if it is not displayed – have to admit that quantum mechanics does not cover everything. How realistic is the case, it is still unknown.

Basic quantum effect, by which conveniently illustrated and experimentally to study this problem – the phenomenon of superposition. If quantum object can be in one state and another state, it can also be in a superposition of these states: in fact in both simultaneously. For example, an atom can be either here or there, or here and there at the same time with a certain probability. This nonlocality leads to interference particles with itself – and that it is fundamentally different from the usual classical states with incomplete information (that is, when the particle is actually located somewhere in a certain place, but we do not know which). Thought experiment with Schrödinger cat – the most famous illustration of this unusual, not having daily analogue nefiksirovannosti quantum state.

In fact, when comparing the quantum and classical, there are two fundamental problems of different levels. The first – is to understand where the possibility of interference disappears large object with itself. With it, quantum mechanics, in principle, the right: this effect is responsible for the phenomenon of decoherence (about it will be discussed below). The problem was narrowed to identify the physical mechanisms of decoherence in different situations and calculate the effect. The second – is to explain how to physically collapses the quantum state of the measurement. This task is beyond the scope of ordinary quantum mechanics; for such an explanation or if you want to modify the theory itself or the proposed construction of quantum mechanics (that is called the interpretation of quantum mechanics). There is not even close to a consensus, and indeed, there is not even agreement on the formulation of the problem itself.

In the recently published in the journal Nature Physics article discusses the first task is. The article describes a new source of decoherence of the quantum state, which is responsible for gravity. No modifications of quantum mechanics, no theories of quantum gravity, nor any other exotic hypotheses is not entered. The effect is completely run by ordinary quantum mechanics to classical background and is not too strong gravitational field.

Decoherence is possible in the most general terms, illustrated by the orchestra. If the orchestra plays smoothly, each instrument plays in time with a wave of his baton, and the overall sound is obtained therefore coordinated, coherent. But if each musician had its distractions, causing unpredictable delays response, the overall sound would be like cacophony. And if the orchestra at the same time consisted of many millions of instruments, instead of contrasting sound works we have just heard some smooth hum.

Approximately disappears coherent quantum process involving many particles. Interference – contrasting alternating bands and attenuation probability – is possible when all the quantum degrees of freedom oscillate synchronously. (See, for example, a detailed story about how this biological molecules used for photosynthesis in the news mechanism of photosynthesis uses vibronic quantum coherence, “Elements “28/07/2014). Interaction with the environment that can knock synchronization and then the interference disappears. It can knock down under the blows of the molecules of the environment, or if our quantum system in a vacuum, with heat absorption and emission of photons. In order to eliminate the damaging effects of the environment requires the most cool sites and to screen it from any external influences. The task is not easy, but for the individual molecules it is quite solvable. That is why one can observe not only the interference of individual particles or atoms, but even large molecules (Fig. 1). However, for larger objects, the size of the order of microns, it is still difficult technical problems.

However, until now there was a general understanding that if a quantum system reliably screened from the environment, quantum coherence it will exist indefinitely. In the new work explains that it is not. Even in a perfectly isolated quantum systems of many particles will be decoherence caused by the effect of the general theory of relativity – the time slowdown in the gravity field.

Fig. 2. Experiment spatial splitting of quantum particles
Fig. 2. Experiment spatial splitting of the quantum particle, which flies in the gravity field from the two paths and reunification interferes with itself. Drawing from the website
The essence of the effect is this. Suppose we have a complex molecule with a large number of degrees of freedom (ie possible fluctuations). We have this molecule, and a pop-up at some point translate into extended state. Now she is not in one place some of the space, and at the same time at two different heights (Fig. 2), it seems to be flying in the gravity field from two paths. When these two paths cross, we translate the molecule again in a localized state, and thus we expect to see the interference. In fact, it turns out the standard atomic interferometer, but only vertically oriented in space. An experimental sounds just fantastic; in fact it is a long time ago realized for individual atoms and Bose condensate and is even used in experiments to measure the force of gravity (gravitational constant measured by new methods, “Elements”, 22.01.2007).

Fig. 2. Experiment spatial splitting of the quantum particle, which flies in the gravity field from the two paths and reunification interferes with itself. Drawing from the website

If the molecule is completely shielded from the chaotic external influences, it would seem, is no problem with interference should not be. Even within the molecule there are any hesitation, they are still the same and proceed to the top of the trajectory, and the bottom. The synchronicity of these oscillations in the cleavage and the reunification of the whole molecule should not be entirely lost. So, the conclusion is broken when you consider the effects of general relativity.

The fact is that in a gravitational field time course slightly retarded, and the stronger the field (more precisely, the deeper potential), the more this slowdown. This effect is very significant in strong gravitational fields; He became particularly famous after the recent film “Interstellar”. But generally, it always works, including in the earth’s gravitational field, and moreover, it is accounted for in navigation systems GPS. Therefore, when the molecule is split into two different flying trajectory in a gravitational field, it experiences a slightly different them along the course of time. And so, when these two molecules are again reunited incarnation, synchronism between the internal vibrations may already be shot down. If this loss of synchronization is essential, coherence is lost and the interference disappears. The molecule undergoes decoherence simply due to the fact that its internal vibrations “entangled in time.”

Why such a seemingly fundamental fact is still not paying attention? Because he is very weak. The relative difference of the time for the two systems separated in the Earth’s gravitational field to a height h, is
x = mghmc2 = rgh2R2,
where rg – is the gravitational radius of the Earth (about 1 cm), and R – the real Earth’s radius (about 6400 km). For the height of the order of microns is obtained entirely insignificant quantity: x~10-22. Therefore, the quantum particle with one degree of freedom should prokolebatsya 1022 times to this effect could be seen – and this is beyond any real experiments. However, the authors note that if we have a system with a large number (N) degrees of freedom, and they vary, then the loss of synchrony amplified N – √ times. For a macroscopic body in which the number of degrees of freedom of the order of Avogadro’s number, the rate of loss of coherence by 12 orders of magnitude faster. Since the typical time scale of vibrations – a picosecond, it turns out that the loss of coherence come very quickly, in milliseconds. And this stress for a completely insulated from external influence body!

Does this work for a new understanding of why real objects around us live in classical, not quantum laws? No, because in this case there is an active interaction with the environment that rapidly destroys the coherence. However, it reveals an important effect, which until then ignored, and which is likely to have to be taken into account when trying to implement a quantum computer and, more generally, any large quantum systems with more expected coherence time. It sets a limit even for a perfectly isolated systems – because a new effect is taken because of gravity, and it is impossible to hide from it.

And finally, from a purely fundamental point of view, this work reveals new aspects of interaction between quantum mechanics and gravity, the two theories which, in a sense, are “at odds” with each other. However, “acrimony” of these two theories related to strong fields and high energies, and under normal circumstances, they get along well (neutrons in the gravitational field of the Earth allow you to test models of dark energy and dark matter, “Elements”, 04.25.2014). But this work and the subsequent theoretical studies (C. Gooding, WG Unruh, 2015. Bootstrapping Time Dilation Decoherence) demonstrate new non-trivial aspects of that relationship. Since these effects are of fundamental interest, they, of course, want to be tested experimentally. This has not yet been done, but the authors hope that, with a reasonable extrapolation techniques to manipulate quantum objects, such tests will be able to implement in the near future.

The fossil turtle was Diapsid

Fig. 1. It might look like an ancestor of turtles Pappochelys rosinae: with reinforced back and inside the belly, long tail and neck, but with short teeth. Drawing from the site

In Germany, in Triassic sediments 240 million years of age, found fossils of reptiles, with the unmistakable signs of turtles. This animal called Pappochelys rosinae, in its morphological structure and lifetime – a real intermediate form between primitive reptiles and turtles. In Pappochelys abdominal ribs were flattened, and in some places are connected, so that the likeness formed plastron; these edges also have a flat top surface, marking the beginning of the formation of dorsal armor. Interestingly, this animal skull appeared diapsidnym with two temporal arcs, whereas modern turtles it anapsidny having no temporal arcs. This finding confirms the molecular phylogeny of turtles, tortoises are placed in one branch with the lizards (Diapsid). If the reconstruction will be believable (and they will still be critically discussed), the classical ideas about the evolution of reptiles will be reviewed.

German paleontologists Rainer Schoch (Rainer R. Schoch) from the State Museum of Natural History in Stuttgart and Hans-Dieter Süss (Hans-Dieter Sues) from the Museum of Natural History in Washington, described a new species of fossil skulls (Fig. 1). They named the turtle extinct Pappochelys rosinae, pointing directly and on its importance for science, and some of the historical details of its study.

Historical details are hidden in the name of the species – it is given in honor of Isabelle Rosin (Isabell Rosin), which masterfully all the prepared fossils, including a relatively complete skeleton, which became standard (Fig. 2). Thus perpetuate the name of the preparator, scientists partly reflect the time-consuming and painstaking process, which is required for the study of fossil remains from the time the discovery in 2006 of nineteen fragmentary skeletons before the publication was 9 years old.

Fig. 2. Here is the skeleton of the type specimen Pappochelys rosinae. This fragmented skeleton, but many bones he survived. Photos of the discussed article in Nature

The generic name is translated as Pappochelys grandfather turtles (Greek pappos – grandfather, chelys – turtle). Pappohelisa be called the grandfather, and because of his old age, and because of its morphological structure, ancestral turtle. The remains of this species were found in Germany, the layers formation Erfurt (Erfurt Formation) srednetriasovogo age (about 240 million years). It is 20 million years older than the fossil turtle Odontochelys, found in China in 2008, which is considered the oldest in this group (see .: Chun Li et al., 2008. An ancestral turtle from the Late Triassic of southwestern China). The alleged ancestor of turtles Eunotosaurus has an age of 260 million years (see .: TR Lyson et al., 2013. Evolutionary Origin of the Turtle Shell). So pappohelis fit in time as the time between the hypothetical ancestor of turtles and specialized descendants.

What to pappohelisa morphology, the researchers note several important, typically “tortoise” features. Firstly, we were pappohelisa abdominal ribs or gastralii forming part intergrown abdominal armor resembling plastron. Secondly, he had pectoral fins T-shaped: with the external, flattened sides are uneven, with a sculpture of the bottom side had thickened, rear (distal) end of the extended edges. These edges are typical of turtles, it can be considered precursors (along with other bone elements) dorsal armor – carapace. In addition, they have elongated trunk vertebrae and specific times of the forelimbs, including an elongated thin blade. Externally this animal looked like a lizard more than a turtle: small size (about 20 cm), with a long tail and a long neck, moving legs, it was relatively quick and, judging by the small blunt teeth on the jaws, it eats worms and middle-sized invertebrates.

So, gather all the information on the morphology, which only can be removed from the disparate parts of the skeleton, the scientists calculated for pappohelisa place on the phylogenetic tree turtles. It is located between Eunotosaurus and Odontochelys with Proganochelys, and the evolution of the latter has led to a whole group of turtles (Fig. 3). So pappohelis – a real transitional form between primitive and specialized lepidosauria turtles. In pappohelisov half shell made and, accordingly, under the half-fitted shell skeleton limbs and their mounts. The authors believe that this kind of a skeleton with a prototype of the plastron could help these animals lead a semi-aquatic lifestyle, move on mild coastal sediments and swim – they were found in the layers of fossil lake.

Fig. 3. a – a schematic representation of the skeleton pappohelisa. b – phylogenetic tree turtles. with – primitive turtle plastron and Odontochelys gastralii pappohelisa, dark gray color shows the bones forming the front surface of the belt. Drawing from the discussed article in Nature

But the most interesting in the skeleton – the structure of the skull. All land animals on the structure of the skull divided into three groups: anapsid, Diapsid and Synapsid. In anapsid skull no one temporal pit, respectively any temporal arc; Diapsid in two temporal pit at Synapsid – one. Modern turtles on the structure of the skull are anapsid as extinct pareiasaur and procolophonidae. Therefore, comparative anatomy, bringing together with the extinct tortoises anapsid, considered their group branched from the trunk before reptilian lizards, snakes and crocodiles.

When there was a molecular phylogeny, the turtle immediately moved above were among diapsidnyh reptiles with lizards. The war between molekulyarschikami and morphology led to the denial of anapsid as such at all (see. Turtles threatened to turn the evolutionary tree of reptiles, “Elements”, 11.22.2013). Like, anapsid, including turtles – it is overgrown with Diapsid temporal arcs. In support of this hypothesis, for example, find undoubted procolophonidae Australothyris smithi one temporal pit. One could even argue as much as necessary about the reliability of the molecular phylogenetic reconstructions, calculate the probability of a tree, has not announced pappohelisy with … two temporal wells. Skull pappohelisa really diapsidny. This once again confirms the obvious position that molecular data – that’s fine, but you can check them really only paleontological finds.

Of course, to rewrite textbooks in zoology is not worth it. It should be ten times to test the findings of German experts. Naturally, scientists are brought up on classical notions of anapsid-Diapsid-sinapsidnoy phylogeny of land vertebrates, will criticize every detail reconstruction pappohelisa, each output of this work. Critical articles have appeared in the first day of publication in the light, surely the debate will be very hot. But to date, molecular phylogeny gave a truer and unambiguous results than comparative anatomy. Perhaps it should be the case with the highly specialized structure plans, such as turtles.

Unicellular algae built compound eye of chloroplasts and mitochondria

Fig. 1. Comparison of microbial eye. a – dinoflagellates family Warnowiidae, b – chlamydomonas, c – fungal spores Blastocladiella. Notes in the text. Figure out the synopsis to the discussion paper in Nature.

Make a chamber eye having a cornea, iris, lens and retina, and can be a single cell component. To this end, representatives of the dinoflagellate family Warnowiidae use complex manner combined organelles – mitochondria, endoplasmic reticulum and chloroplasts former, lost the ability to photosynthesize.

Eye – is a classic example of a complex organ consisting of different tissues, which brings the body to benefit as a whole. Even Darwin asked questions about how animal compound eye could be formed gradually in the course of evolution. What Darwin replied that complex organs could well be formed gradually, because even imperfect eyes can give the body a slight advantage. For example, the light-sensitive cells, without additional devices may only help to determine the general direction of light. But this is better than total blindness.

Interestingly, a classic example of a complex organ like the eye chamber, may develop even in unicellular organisms. These eyes with all the necessary components – the cornea, iris, lens and retina – have representatives of plankton – dinoflagellates family Warnowiidae.

Single-celled creatures with complex eyes in the cytoplasm of cells have been described in the early twenties of the last century (see. Charles Atwood Kofoid & Olive Swezy, 1921. The free-living unarmored dinoflagellata). Then the researchers and had no idea that such complex eyes belong to microbes. It was therefore decided that the eyes in the cytoplasm – is nedoperevarennye remnants of jellyfish that feeds on plankton. Such a hypothesis long persisted because the representatives of dinoflagellates family Warnowiidae very rare. Furthermore, until now not chosen conditions for cultivating these microorganisms in a laboratory, which is why they and nowadays difficult to study.

Fortunately, over the past hundred years the arsenal of biological methods has expanded dramatically. Now, scientists can learn a lot of useful information even from just some few cells. For single cells is now possible to analyze the DNA sequence, gene expression levels, and even some amount of proteins. Only with the development of sensitive and accurate genetic methods scientists have carefully demonstrated that the compound eyes of dinoflagellates – it is their own development, rather than the remains of the victims.

An international team of researchers gathered a few dozen cells dinoflagellates family Warnowiidae off the coast of Japan and Canada. Scientists have identified the individual components of bacterial eye and analyzed the composition of nucleic acids. It turned out that the “retina” eye dinoflagellates is part of a complex system of chloroplasts, which stopped working in the specialty (dinoflagellates family Warnowiidae long ago lost the ability to photosynthesize). Nevertheless, in the old memory are continued to operate several specific genes of chloroplasts.

Even if the microorganisms found a structure very similar to the compound eye, which guarantees that it reacts to light? Studies show that reacts. Firstly, it was recently shown that the morphology of the “retina” eye dinoflagellates family Warnowiidae light-dependent (see .: S. Hayakawa et al., 2015. Function and Evolutionary Origin of Unicellular Camera-Type Eye Structure). Under the influence of light inner membrane vesicles of organelles became more elongated and flat. In the same article in the “retina” of these dinoflagellates we found gene expression of rhodopsin-like bacteria. The proteins in this group allow to feel the direction of the light and other microorganisms that have simple eyes – such as Chlamydomonas and fungus Blastocladiella, floating spores which also provided with photosensitive sensors. But there are other mechanisms of perception of the world: for example, using a light-sensitive protein euglena adenylate cyclase activated by light.

All microorganisms having eyes, these organs are arranged differently. In Chlamydomonas, like dinoflagellates family Warnowiidae, reacts to light part of the chloroplast (chloroplast only they work). The photosensitive spot on the edge of the chloroplast of Chlamydomonas contain rhodopsin, which partially shield the granules with the pigments carotenoids (Fig. 1). Screening photosensitive sensors with at least one hand it is necessary that the body could determine the direction of light. Others have “sighted” microorganisms – Euglena – eye is not related to the chloroplasts. In Euglena photosensitive proteins embedded in the membranes of special thick stack at the base of the flagellum. The direction of light provide granules with a pigment gematohromom. The spores of the fungus Blastocladiella device photosensor similar – rhodopsins membrane organelles located in the neighborhood with the flagellum, and near them are lipid vesicles, also likely to provide direction of the light incident on the photosensitive organelles.

Interestingly, the plastids, on the basis of which have different single-celled independently developed “eyes” have different origins: so, dinoflagellates Warnowiidae and Cryptophyta algae Guillardia secondary plastids (descended from symbiotic red algae – a representative of the eukaryotes), and in Chlamydomonas – primary, from symbiotic cyanobacteria. This is another argument in favor of the “eyes” on the basis of plastids developed in unicellular eukaryotes, many times independently. Among the many examples of unicellular generally convergent eye development of various “scrap” materials (often plastids, but not always, often using rhodopsin, but do not always).

All microbial eyes, investigated before, found only some simplified analogues of the retina (the membrane with proteins respond to light and the pigment granules, replacing a pigmented retinal cells of a multicellular eyes). A family Warnowiidae dinoflagellates have not stopped, and added to their eye still lens consisting of membranes of the endoplasmic reticulum, the focusing light on “retina” (Fig. 2). The lens significantly improves the image sharpness. Also dinoflagellates appeared shell eyes – the cornea, which consists, as scientists have found, from a plurality of connected into a single system of mitochondria. It turns out interesting and rather rare example of convergence in the two levels of life – unicellular and multicellular. Interestingly, in the creation of the compound eye of the microorganism involved, and both types of endosymbionts (mitochondria and chloroplasts), and his own membrane (endoplasmic reticulum).

Dinoflagellates family Warnowiidae feed on other plankton representatives, including other dinoflagellates. Scientists suggest that the eye helps them to monitor the movements of their victims, which Warnowiidae can hunt using cell “harpoons” – nematocysts. Some of dinoflagellates, which feed Warnowiidae, fluoresce. Therefore, they can be quite clearly seen only need to have an eye. So it is quite possible that we will soon know the answer to the question whether they see each other microbes.

Another notable feature of dinoflagellates – is constantly condensed chromosomes, polarizing light. Does the compound eye Warnowiidae distinguish polarized light, yet to be verified. But the internal structure of their “retina” with hundreds of parallel oriented membrane vesicles really similar to the polarizers, which are used, for example, in the sunglasses and the lenses of cameras.

A new variety of rice will help reduce greenhouse gas emissions

Scientists from Sweden received the genetically modified rice plantation is hardly emit methane. For this figure supplied by one of the genes of barley, stimulating the deposition of starch in the stems and seeds of the plant. Grains such rice more nutritious, and in the roots, on the contrary, less stored carbohydrates. Therefore, living in the roots of rice soil bacteria gets less raw materials for the synthesis of methane.

Methane – a greenhouse gas malignant, its molecules absorb infrared active molecule of carbon dioxide. The contribution of methane to the increase in temperature is observed with ever since mankind began to actively influence the Earth’s climate is about 20%. The main source of methane, which arose due to human activity – is rice fields. According to various estimates, they produce between 7 and 17% of atmospheric methane. And as humanity is growing and in need of a growing number of food in the future, the number of rice fields likely to increase significantly. Therefore, forward-thinking researchers from Sweden have now have a variety of rice, which almost does not produce methane. If farmers have switched to this figure, the contribution of mankind to global warming have been able to drastically reduce.

Previously, the same team of scientists found in barley gene transcription factor SUSIBA-2, working mainly in the seeds of plants and enhances the operating time of the starch. Starch – a polymer in which a plant stockpile sugars formed during photosynthesis. If you make a gene SUSIBA-2 to work actively in certain tissues of the plant, there will flock sugar. It is clear that such a redistribution in the rice stocks of sugar from the roots to stems and grain could help reduce methane emissions plantations of this plant.

The fact that methane is not synthesized by the rice and certain bacteria living on its roots. The raw materials for the synthesis of methane bacteria use acetate, and other carbon-containing molecules formed after the collapse of the sugar. Therefore, the less sugar will be supplied to the roots, the less will feel comfortable methane-producing bacteria, and the less methane will be released into the atmosphere rice fields.

Scientists have genetically modified rice plants in which the working of the transcription factor gene of barley SUSIBA-2. The control system is also borrowed from the genome of barley: the gene he begins to actively work only in the presence of a sufficient amount of sugar. Accumulating transcription factor thus enhances the activity of its own gene and includes other genes necessary for bonding sugars to starch. It turns out that the system works more actively, as there is sugar free. But to begin its operation need to sugar present in free form in sufficient quantities, so it will not be active in all parts of the plant.

The resulting rice researchers Jachmeneva factor SUSIBA-2 actively accumulating in the seeds and stems of plants, formed in the leaves in a barely noticeable amounts, but the roots are not synthesized at all. The same pattern was observed with the activity of genes involved in the processing of sugar to starch. Thus scientists were able to redirect the flow of sugars in the plant, so that they both can be stowed in the active seeds and stems, and not in roots. In addition to achieving the main goal – to reduce the formation of methane – it turned out that the seeds are more nutritious rice and dry weight increased.

All methanogenic bacteria have coenzyme F420. In its specific fluorescence can be easily distinguished from the rest of methanogenic bacteria. Scientists have studied using fluorescence microscopy roots of transgenic rice grown under field and laboratory conditions, and found that in both cases it methanogenic bacteria on the roots smaller than the ordinary rice (Fig. 2). Not surprisingly, the landing of the methane produces less rice.

Interestingly, the effectiveness of the system depended on the time of year and day, because it includes a system of redistribution of sugars only when enough of their operating time. Thus, the difference in the morning release of methane and conventional planting of transgenic rice was small, but increased sharply in the afternoon. In the summer of transgenic rice produces less methane than the fall. At the peak achievements of sugars genetically modified plants emit only 0.3% of the amount of methane generated in the usual rice.

Genetically modified rice has already been three years of field trials in several regions of China. But because these plants affect the balance of soil bacteria to spread the new rice varieties need longer and more detailed studies of the composition of the soil. In addition, now widely disseminate a new variety of rice will not work due to mistrust of society to technology GMOs. Therefore, the researchers plan to get rice with the same genetic modification by traditional methods – using selection. Researchers estimate that it will take about ten years.