Squeezing light into quantum dots

first_img Quantum dots as midinfrared emitters Explore further Now, though, that view has changed. Kambhampati says that he and his colleagues at McGill University in Montreal, Quebec, Canada have figured out how to train lasers to properly drive a quantum dot so that light amplification is in line with theories developed years ago. Ryan Cooney, Samuel Sewall, D.M. Sagar and Kambhampati present the results of their experiment in Physical Review Letters: “Gain Control in Semiconductor Quantum Dots via State-Resolved Optical Pumping.”“We figured that if you took the quantum dot that most had given up on,” continues Kambhampati, “that we could figure out why it wasn’t working as predicted, and try to determine what went wrong. We found out that it was all in the way that experiments were done. By virtue of the available driving lasers, previous experiments were coincidentally done under conditions that were actually best for blocking the useful amplification process. Quantum dots may actually be more useful for light amplification than previously imagined. They have the potential to be very powerful.”Kambhampati and his peers discovered that the clue to getting the quantum dots to properly amplify light was in the color of the laser light used to power the dot. “Each quantum dot is different,” Kambhampati explains. “Everything absorbs different colors of light, and that is true of quantum dots. We found that you have to know which colors works for which dots. Certain colors will produce amplification as theoretically predicted. The color of the laser being used to pump the dot is one of the most important factors.” Once you know that information, it is possible to use the laser to drive the quantum dot appropriately. The Montreal group “trained” their lasers to find the correct color in order to pump the quantum dot in such a manner as to amplify the light. In this manner, they were able to stimulate emission in quantum dots using specific interactions. The way that these quantum dots are pumped, “squeezing” light into the box-like structure, makes a big difference in the output seen.Even though Kambhampati can see uses for such light amplifiers down the road – especially in terms of fiber optics and long-distance telecommunications, he acknowledges that there are some fairly significant hurdles to overcome. The first problem is that right now the lasers used to drive the dots are prohibitively expensive for commercial use. “Telecom companies don’t have the same scientific lasers that we have to produce different colors. The eventual goal is to be able to make small, cheap practical lasers that can be used commercially.” He says that there are already efforts underway to figure out how to fine tune lasers to work in this manner, but “sometimes there is a long path from science to engineering to manufacturing.”Kambhampati remains hopeful, however. And he also points out that there are some other interesting things to learn on a fundamental from this experiment. “We saw some things that no one has seen before – things not seen in a quantum well.” In addition to long-term commercial uses, it is possible that this experiment could help other investigations dealing with extremely short pulses, or that require an efficient white light source.“Really, this is just the beginning. A number of interesting ideas, fundamentally and practically, may come out of this ability to control the output of a quantum dot.”More information: Ryan R. Cooney, Samuel L. Sewall, D.M. Sagar, and Patanjali Kambhampati, “Gain Control in Semiconductor Quantum Dots via State-Resolved Optical Pumping.” Physical Review Letters (2009). Available online: link.aps.org/doi/10.1103/PhysRevLett.102.127404 . Copyright 2009 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. (PhysOrg.com) — “Quantum wells have been instrumental in telecommunications, enabling light amplification,” Patanjali Kambhampati tells PhysOrg.com, “but theory has suggested that a very small – colloidal – quantum dot could amplify light even better than a quantum well. There have been problems, however, in getting lasers to work properly with colloidal quantum dots, so focus has shifted to other types of structures.”center_img Citation: ‘Squeezing’ light into quantum dots (2009, April 1) retrieved 18 August 2019 from https://phys.org/news/2009-04-quantum-dots.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Using CNTs as infrared sensors

first_img(PhysOrg.com) — Semiconductors provide the bases for many different avenues of device research. Indeed, many of the technological devices that are commonplace in our society are reliant on semiconductors. However, as we increasingly explore the opportunities afforded on the nanoscale, new semiconductor materials are needed. One of the more promising semiconducting materials at this level is the carbon nanotube (CNT). More information: Lai, et al., “Engineering the band gap of carbon nanotube for infrared sensors,” Physical Review Letters (2009). Available online: link.aip.org/link/?APPLAB/95/221107/1 Copyright 2009 PhysOrg.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of PhysOrg.com. Citation: Using CNTs as infrared sensors (2010, January 4) retrieved 18 August 2019 from https://phys.org/news/2010-01-cnts-infrared-sensors.html Explore furthercenter_img “There is great promise in using a carbon nanotubes for sensors.” Ning Xi tells PhysOrg.com. Xi is John D. Ryder Professor of Electrical and Computer Engineering at Michigan State University, and leads a group that is working on engineering CNT band gaps for use as infrared sensors. Xi worked with Kin Wai Chiu Lai, Carmen Kar Man Fung and Hongzhi Chen at Michigan State, and Tzyh-Jong Tarn at Wasington University in St. Louis to develop a process that is described in Applied Physics Letters: “Engineering the band gap of carbon nanotube for infrared sensors.” This project is supported by the Office of Naval Research.“For semiconductor material, the band gap is one of the most important parameters,” Xi explains. “The band gap represents how much energy is needed to move an electron. In order for the electron to move, it has to be able to jump over this gap. You have to change the composition of the material in order to change the band gap, and this is very difficult. People have been trying all kinds of ways to do this for years.”As far as sensors are concerned, using CNTs with different band gaps can help pinpoint different types of light. “Infrared light has a certain wavelength,” Xi says. “You need a certain band gap to detect this. If you have nanotubes with different band gaps, you can design a sensor to detect different spectrum of infrared. And since these nanotubes are so small, arraying different CNTs with different band gaps is possible.”In order to engineer the band gaps so that they can provide the semiconducting sensors, Xi and his colleagues created a process of stripping away layers of multi-wall CNTs. “The interesting thing with carbon nanotubes is that the band gap depends on the radius. If you have a multi-wall nanotube, you can peel away the outer layer to change the radius. And that changes the band gap as well. Instead of changing the semiconductor material, it is possible to tune the band gap to the proper value, one step at a time.”Xi and his colleagues and collaborator developed a process that allows them to use feedback control to remove layers of multi-wall CNTs. “We were able to do this experimentally, with relative ease compared to earlier processes for band gap tuning,” Xi points out. “We were able to generate different types of carbon nanotubes with different band gaps, and able to detect multiple wavelengths of light across a spectrum.” Being able to tune a band gap without having to make a new material is a big step forward in semiconductors, and Xi hopes that this process can be used for other purposes. “We are primarily interested in infrared nanosensors, but there could be other applications for this technology.” This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Boron Nitride Nanotubes More Amenable Than Carbonlast_img read more

Paper stirs up controversy over the nature of the quantum wave function

first_img Explore further (Phys.org) — Back in November, a paper posted to a preprint server arXiv by three British physicists prompted some heated debate regarding the nature of the quantum wave function, a probability function that physicists use to help them better understand the quantum world. At the time, the three refrained from joining in on subsequent discussions on the paper due to pending acceptance of the paper in the journal Nature Physics. Now that the paper has been accepted and printed, the three, Matthew Pusey, Jonathan Barrett and Terry Rudolph are openly defending their assertion that the wave function is real, not some function that is dependent on available information for the user when using it. At the heart of the issue are the contrasting ideas on the very nature of quantum mechanics itself. In their paper, the British physicists contend that the wave function is not just a tool that can be used for statistical purposes, but can measure actual real things. Others have suggested that it cannot be a real tool because of inconsistencies in observable quantum mechanics, such as entanglement. Because of such inconsistencies, physicists such as Einstein contended that our knowledge or model of quantum mechanics is incomplete, not wrong. It’s possible the thinking goes, as an example, that because two distant entangled particles react in identically the same way at the same time, seemingly sharing information faster than the speed of light, that there is some new element of quantum mechanics at work that would allow for such a real world phenomenon to exist, rather than an example of the failure of quantum mechanics theory itself. Another example is the differing views regarding Schrödinger’s cat. Some might say the wave function could be used to prove whether the unseen and thus un-measurable cat is truly dead or alive, whereas others, such as Einstein would say that because the inquisitor has only partial knowledge, no true answer can be given.The problem with proving which view is true is the theory that most agree on and that is that quantum states can be changed simply by measuring them, which means, that as things stand now, physicists have no way of proving what state existed prior to measurement. But that doesn’t mean the wave function can’t be used to measure a quantum state, Pusey et al say, because the true state did exist before measurement occurred. At that moment it was real, they say, as is the wave function and they believe they have proved it. Journal information: Nature Physics Does the quantum wave function represent reality? © 2012 Phys.Orgcenter_img More information: On the reality of the quantum state, Nature Physics (2012) doi:10.1038/nphys2309Quantum states are the key mathematical objects in quantum theory. It is therefore surprising that physicists have been unable to agree on what a quantum state truly represents. One possibility is that a pure quantum state corresponds directly to reality. However, there is a long history of suggestions that a quantum state (even a pure state) represents only knowledge or information about some aspect of reality. Here we show that any model in which a quantum state represents mere information about an underlying physical state of the system, and in which systems that are prepared independently have independent physical states, must make predictions that contradict those of quantum theory.via Nature News Citation: Paper stirs up controversy over the nature of the quantum wave function (2012, May 9) retrieved 18 August 2019 from https://phys.org/news/2012-05-paper-controversy-nature-quantum-function.html This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. The researchers’ definition of a physical property is illustrated here. Image (c) Nature Physics (2012) doi:10.1038/nphys2309last_img read more

Uncanny Valley robots essay resurfaces 42 years later

first_img Too scary to be real, research looks to quantify eeriness in virtual characters Citation: Uncanny Valley robots essay resurfaces 42 years later (2012, June 13) retrieved 18 August 2019 from https://phys.org/news/2012-06-uncanny-valley-robots-essay-resurfaces.html (Phys.org) — An essay on robots by a professor in Japan over 40 years ago has just got its official translation. Many in robotics and other science circles will say better late than never for an official translation of Yasahiro Mori’s paper, “The Uncanny Valley” which was published in a Japanese journal called Energy 42 years earlier. The essay has generated interest about the extent and limitations of making robots more and more human-like in human-robot interaction. An English translation was done in 2005 but the translation that has been authorized and and reviewed by Mori was published Tuesday in IEEE Spectrum. “I have noticed that, in climbing toward the goal of making robots appear human, our affinity for them increases until we come to a valley (Figure 1), which I call the uncanny valley.” That observation from his original essay is what sparked conversations and interest among robotic designers over the years. Mori maintains that humans are drawn to human-like robots with positive feelings of affinity until the robot moves or reveals itself in such a way that triggers the person’s realization that it is not human. Then it becomes “uncanny” or in popular-culture terms, creepy. Affinity is lost. In his essay, Mori expressed this experience in a graph, and he also offered an example, the prosthetic hand. The human being gets an “eerie sensation,” he said, when realizing that the hand is not real. “We could be startled during a handshake by its limp boneless grip together with its texture and coldness. When this happens, we lose our sense of affinity, and the hand becomes uncanny. In mathematical terms, this can be represented by a negative value.” He adds that when a prosthetic hand that is near the bottom of the uncanny valley starts to move, the sensation of eeriness intensifies.The official translation on Tuesday is accompanied by an interview with Mori, who can look at the validity of his remarks 42 years later, when robotics has gone through so many developments. A counterpoint to the popularity of Mori’s essay has been the contention that the essay was an essay, after all, of limited scientific value.Mori said, “I have read that there is scientific evidence that the uncanny valley does indeed exist; for example, by measuring brain waves scientists have found evidence of that. I do appreciate the fact that research is being conducted in this area, but from my point of view, I think that the brain waves act that way because we feel eerie. It still doesn’t explain why we feel eerie to begin with.“ Mori said that pointing out the existence of the uncanny valley was intended as advice for people who design robots rather than a scientific statement itself.Mori said he still thinks that designers should steer clear of making robots too lifelike, falling into the valley. ” I have no motivation to build a robot that resides on the other side of the valley…Why do you have to take the risk and try to get closer to the other side?” He said he did not even find it interesting to develop a robot that looks “exactly” like a human.Mori spoke approvingly about Asimo as “invigorating,” a robot inviting positive feelings but appearing as different from humans.The two translators of the essay are Karl F. MacDorman, associate professor of human computer interaction at the School of Informatics, Indiana University. and Norri Kageki, a journalist who writes about robots. Explore further More information: spectrum.ieee.org/automaton/ro … s/the-uncanny-valleyspectrum.ieee.org/automaton/ro … n-the-uncanny-valley © 2012 Phys.Org Image: Wikipedia. This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

Chinese team builds first quantum router

first_img(A) Illustration of a genuine quantum router. The control photon can be in arbitrary superposition states with coecients c0; c1 that determine the path of the signal photon. (B) The entanglement-based approach to implementation of a genuine quantum router. With a bit of pre-shared entanglement, the quantum router can be realized with linear optical devices. The control coecients c0; c1 are imprinted through operation on the control photon alone with a polarization rotator and a lter. The routing is realized with a polarization beam splitter (PBS) and a wave plate on the signal photon. Image from arXiv:1207.7265v1 [quant-ph] This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Physicists build first single-photon router © 2012 Phys.org Explore further More information: Experimental demonstration of an entanglement-based quantum router, arXiv:1207.7265v1 [quant-ph] arxiv.org/abs/1207.7265AbstractWe report an experiment that demonstrates full function of a quantum router using entangled photons, where the paths of a single-photon pulse are controlled in a coherent fashion by polarization of another single photon. Through a projective measurement, we prepare the polarization of the control photon in arbitrary superposition states, leading to coherent routing of the target photon in quantum superposition of different paths. We demonstrate quantum nature of this router through optical measurements based on quantum state tomography and show an average fidelity of $(93.24pm 0.23)%$ for the quantum routing operation.center_img The trick in routing quantum data is that reading the information from a signal that tells a router where to send data, causes that data or signal to be destroyed; that’s just how quantum mechanics works, so the ordinary way of routing data on a network won’t work. To get around that problem, the researchers used two of the special properties of quantum particles, namely, entanglement, whereby whatever happens to one, automatically happens to another and the fact that a particle is capable of representing two states at once (i.e. both 1 and 0).To build their router the team first generated a photon with superposition (one that has both horizontal and vertical polarization states); they then converted the photon to two entangled photons that also had superposition states. Then they treated one of the entangled pair as the control signal and the other as the data signal. When the control signal is read, and destroyed, the router gains the information it needs to know regarding which of two optical fiber cables to send the data signal, and thus, routes the data signal down the desired path.The researchers aren’t claiming they’ve come up with a solution for building a quantum Internet, as clearly their router is only capable of routing a single cubit, but it does demonstrate that routing quantum data is possible, and that’s something that until now, no one else has been able to do. And it also gives hope to researchers that someday a new and different type of quantum router will be created that really will allow for a true quantum Internet, and if that happens, data transmission will likely become so fast, that it will cease to be a topic of conversation. Citation: Chinese team builds first quantum router (2012, August 7) retrieved 18 August 2019 from https://phys.org/news/2012-08-chinese-team-quantum-router.html Journal information: arXiv (Phys.org) — With all the talk of quantum computers, little notice has been made of work on what is known as a quantum Internet, which is where data is sent across a web of computers via devices that work at the quantum, rather than atomic level, thereby increasing the speed of the whole system. The holdup at this point is in creating devices capable of routing such information. Now it appears that a team of physicists working from Tsinghau University in China have proven that it’s possible to do so. They have, as they describe in the paper they’ve uploaded to the preprint server arXiv, built a working quantum router capable of routing one cubit.last_img read more

Ex nihilo Dynamical Casimir effect in metamaterial converts vacuum fluctuations into real

first_img This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only. Researcher Pasi Lähteenmäki discussed the challenges he and his colleagues – G. S. Paraoanu, Juha Hassel and Pertti J. Hakonen – encountered in their study. Regarding their demonstration of the dynamical Casimir effect using a Josephson metamaterial embedded in a microwave cavity at 5.4 GHz, Lähteenmäki tells Phys.org that the main challenge in general is to get high-quality samples. In addition, Lähteenmäki adds, they had to ensure that the origin of the noise is quantum and not some unaccounted source of excess noise, such as thermal imbalance between the environment and the sample, or possibly leakage of external noise.Modulating the effective length of the cavity by flux-biasing the SQUID (superconducting quantum interference device) metamaterial had its challenges as well. “The pump signal needs to be rather strong, yet at the same time one wants to be sure that no excess noise enters the system through the pump line, Lähteenmäki notes, “and good filtering means high attenuation, which is a requirement contradictory to a strong signal. Also,” Lähteenmäki continues, “at 10.8 GHz the pump frequency is rather high – and at that frequency range both the sample and the setup is rather prone to electrical resonances which can limit the usable frequencies.” In short, the flux profile needs to be such that the pumping doesn’t counteract itself. In addition, trapping flux in SQUID loops can also become a problem, limiting the range of optimal operating points and causing excess loss.The researchers also showed that photons at frequencies symmetric with respect to half the modulation frequency of the cavity are generated in pairs. “In general, with frequency locked signal analyzers today the extraction of this correlation is not particularly problematic – especially since the low noise amplifier noise is not correlated at different frequencies,” Lähteenmäki explains. That said, issues related to data collection and averaging include amplifier gain drift and phase randomization of the pump signal (relative to the detection phase) if the state of the generator is changed. “The noise temperature of the low noise amplifier sets some limits to the amount of data that needs to be collected, especially in the case where one is operating in the regime of low parametric gain.” More information: Dynamical Casimir effect in a Josephson metamaterial, PNAS Published online before print February 12, 2013, doi:10.1073/pnas.1212705110 Journal information: Proceedings of the National Academy of Sciences Citation: Ex nihilo: Dynamical Casimir effect in metamaterial converts vacuum fluctuations into real photons (2013, March 8) retrieved 18 August 2019 from https://phys.org/news/2013-03-nihilo-dynamical-casimir-effect-metamaterial.html (Phys.org) —In the strange world of quantum mechanics, the vacuum state (sometimes referred to as the quantum vacuum, simply as the vacuum) is a quantum system’s lowest possible energy state. While not containing physical particles, neither is it an empty void: Rather, the quantum vacuum contains fluctuating electromagnetic waves and so-called virtual particles, the latter being known to transition into and out of existence. In addition, the vacuum state has zero-point energy – the lowest quantized energy level of a quantum mechanical system – that manifests itself as the static Casimir effect, an attractive interaction between the opposite walls of an electromagnetic cavity. Recently, scientists at Aalto University in Finland and VTT Technical Research Centre of Finland demonstrated the dynamical Casimir effect using a Josephson metamaterial embedded in a microwave cavity. They showed that under certain conditions, real photons are generated in pairs, and concluded that their creation was consistent with quantum field theory predictions. Copyright 2013 Phys.org All rights reserved. This material may not be published, broadcast, rewritten or redistributed in whole or part without the express written permission of Phys.org. Light particles illuminate the vacuum Explore further Lastly, the team also found that at large detunings of the cavity from half the modulation frequency, they found power spectra that clearly showed the theoretically-predicted hallmark of the dynamical Casimir effect. “Large detunings imply low intensity of generated radiation,” notes Lähteenmäki. “This means long averaging times, so the system should be kept stable for a long period. Also, the system needs to be fairly resonance-free over a large range of frequencies to get decent data – and/or one needs to know the characteristics of these resonances and noise temperature of the low noise amplifier rather well.”Lähteenmäki points out that addressing these issues required a number of insights and innovations. “We combated amplifier drift by continuously switching the pump on and off, and recording the difference in the observed output power, suitable operating points were searched for using trial and error, and trapping the photon flux was eliminated by applying a heat pulse to the sample and letting it cool down again. The researchers also magnetically shielded the sample with a superconductive shield, and minimized the effect of losses by changing the coupling of the existing samples by making different valued vacuum coupling capacitors with focused ion beam (FIB) cuts.”However,” Lähteenmäki stresses, “our biggest issue – ruling out the source of classical noise as opposed to quantum noise – was accomplished primarily by characterizing the sample and the environment well” Thermal imbalance was ruled out by the symmetry of the sparrow-tail shape of the noise spectrum.It was essential for the scientists to clearly demonstrate that the observed substantial photon flux could not be assigned to parametric amplification of thermal fluctuations. “By characterizing the parametric gain with a network analyzer,” Lähteenmäki notes, “we found that in order to explain the amount of noise one gets, the device would need to have significantly higher gain than is observed if the only source of noise was thermal.” Moreover, confirming that photon pair creation is a direct consequence of the noncommutativity structure of quantum field theory was equally important. “Basically the experimental results fit the theoretical predictions rather well – and in the absence of other sources of noise, the theory implies that we should get no output from this sort of device. Since we see output consistent with the theoretical predictions, the conclusion was logical.”Moving forward, Lähteenmäki describes next steps in their research. “Instead of a continuous wave pump, we could have a straight flux line and feed it with a step-like flux pulse,” Lähteenmäki says. “This would allow the creation of an analogue to a black hole event horizon. In fact,” he adds, “we’re hoping to create an artificial event horizon in a metamaterial similar to the one used in our current research and study Hawking radiation originating from it. Also, it would be nice to be able to run experiments on Bell’s inequalities.” His personal interests, Lähteenmäki says, are fundamental quantum mechanics, quantum information and properties of the vacuum itself.”The obvious applications for these devices,” he notes, “come from quantum computation, and in general they may serve as components for multitude of sensitive measurements. I believe the interest towards low loss metamaterials is high and the field is just getting started. Our results show that these devices have potential and can offer a fruitful platform for many experiments and perhaps practical devices as well. Improving such devices – especially eliminating the losses and making them function more robustly – would allow them to create a general purpose component suitable for creating entangled microwave photon pairs, low noise amplification, squeezed vacuum, and other functions that can be very useful for quantum computation and general experiments in the quantum mechanics and in studying the vacuum.”Another possibility, Lähteenmäki adds, is to create a metamaterial which would allow them to stop signal propagation in the material entirely and allow them to resume it later. “This would act as a kind of slow light memory that would store the photon for later use.”Other areas of research might benefit from their study as well, Lähteenmäki says. “There are some connections to cosmology, the big bang, cosmic inflation, and other areas. These metamaterials could possibly offer an analogy to such events and serve as a platform to simulate the evolution of such conditions. Who knows,” he ponders, concluding that “perhaps we’d find clues to the mysteries of dark matter and dark energy or other fundamental questions from such systems.” (a) Equivalent electrical and mechanical circuits: the modulation of the Josephson inductance in the metamaterial by a magnetic φext varies the wave length λ with respect to the cavity length, which is analogous to modulating the effective length d of the cavity by mechanical means. The coupling capacitor is equivalent to a semitransparent mirror. (b) Schematics of the measurement setup. The metamaterial sample is a 4-mm-long coplanar waveguide with 250 embedded SQUIDs, each junction having a critical current of ~ 10 μA. The modulation of the flux through the SQUIDs is realized through a lithographically fabricated spiral coil underneath the metamaterial. (c) Resonant frequency ωres/2π vs. reduced magnetic flux φext/φ0 without the pump signal; the DC operating point for DCE experiments is denoted by a green circle. The inset displays the measured phase of the scattering parameter S11 while sweeping frequency, which yields d arg(S11)/dφext = d arg(S11)/dfÍdf/dφext . The steepness of the variation in the phase arg(S11) governs the effective “movement of the mirrors”. Copyright © PNAS, doi:10.1073/pnas.1212705110last_img read more

Carbyne is stronger than any known material

first_img Explore further (Phys.org) —A paper on Arxiv presents a detailed look at the properties of carbyne, stronger than graphene and diamond, a true supermaterial. The paper is titled, “Carbyne from first principles: Chain of C atoms, a nanorod or a nanorope?” Authors are Mingjie Liu, Vasilii I. Artyukhov, Hoonkyung Lee, Fangbo Xu, and Boris I. Yakobson, from Rice University, in Houston, from the departments of mechanical engineering and materials science, chemistry, and the Smalley Institute for Nanoscale Science and Technology. They have calculated the properties of carbyne. Described as a chain of carbon atoms that are linked by alternate triple and single bonds or by consecutive double bonds, carbyne is of special interest, chemists find, because it is stronger, and stiffer than anything that they have seen before. The discovery of carbyne is not entirely new. Explorations of carbyne have their own history. Carbon ‘grapevine’ may store hydrogen Citation: Carbyne is stronger than any known material (2013, August 20) retrieved 18 August 2019 from https://phys.org/news/2013-08-carbyne-stronger-material.html Journal information: arXiv Carbyne under tension. (a) DFT calculations of energy as a function of strain ɛ. The electronic density of carbyne (polyyne) (b) in equilibrium and (c) under tension shows a more pronounced bond alternation in strained carbyne. (d) Bond length alternation and (e) band gap increase as a function of strain. Credit: arXiv:1308.2258 [cond-mat.mtrl-sci]center_img Indications of naturally-formed carbyne were observed in such environments as shock-compressed graphite, interstellar dust, and meteorites, said the authors. Recently, chains with length of up to 44 atoms have been chemically synthesized in solution. Elsewhere, a Rice University report on carbyne research in 2011 said that while carbyne is considered an exotic material, recent experiments showed it can be synthesized and stabilized at room temperature, where the storage is mainly of interest.Of special interest in the new paper on carbyne is that research by the Rice team indicates just how strong and stiff is this supermaterial. They were able to calculate its properties. In presenting a summary and conclusions of their research, the authors said that they were able to create a comprehensive portrait of carbyne. Some key points are as follows. It has an extreme tensile stiffness, stiffer by a factor of two than graphene and carbon nanotubes—and a specific strength surpassing that of any other known material. Its flexibility is between those of typical polymers and double-stranded DNA, they continued, with a persistence length of ~14 nm. A combination of unusual mechanical and electronic properties, they said, is of great interest for applications in nanomechanical systems, opto-/electromechanical devices, strong and light materials for mechanical applications, or as high–specific-area energy storage matrices.Their research was supported by the Robert Welch Foundation, a source of funding for chemistry research, and the Department of Energy. More information: Carbyne from first principles: Chain of C atoms, a nanorod or a nanorope? arXiv:1308.2258 [cond-mat.mtrl-sci] arxiv.org/abs/1308.2258AbstractWe report an extensive study of the properties of carbyne using first-principles calculations. We investigate carbyne’s mechanical response to tension, bending, and torsion deformations. Under tension, carbyne is about twice as stiff as the stiffest known materials and has an unrivaled specific strength of up to 7.5*10^{7} Nm/kg, requiring a force of ~10 nN to break a single atomic chain. Carbyne has a fairly large room-temperature persistence length of about 14 nm. Surprisingly, the torsional stiffness of carbyne can be zero but can be `switched on’ by appropriate functional groups at the ends. We reconstruct the equivalent continuum-elasticity representation, providing the full set of elastic moduli for carbyne, showing its extreme mechanical performance (e.g. a Young’s modulus of 32.7 TPa with an effective mechanical thickness of 0.772 {AA}). We also find an interesting coupling between strain and band gap of carbyne, which is strongly increased under tension, from 3.2 to 4.4 eV under a 10% strain. Finally, we study the performance of carbyne as a nanoscale electrical cable, and estimate its chemical stability against self-aggregation, finding an activation barrier of 0.6 eV for the carbyne-carbyne cross-linking reaction and an equilibrium cross-link density for two parallel carbyne chains of 1 cross-link per 17 C atoms (2.2 nm).via Arxiv Blog © 2013 Phys.org This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img

Rover underice prototype may lead to Europa search

first_img NASA plots daring flight to Jupiter’s watery moon (Phys.org) —Scientists at NASA’s Jet Propulsion Laboratory (JPL) have been working on a device that may one day explore the underside of ice on Europa, Jupiter’s moon. NASA completed an early prototype of the rover it hopes will give us more information about Europa, with its abundant water and energy and chemistry. A National Geographic video shows the rover, called BRUIE (Buoyant Rover for Under-Ice Exploration) being taken for a run in Alaska. The team is interested in Europa, with its frozen, fissured surface and all. NASA’s notes on Europa tell us it is an icy world slightly smaller than Earth’s moon. A unique feature about Europa in the solar system is its global ocean of water in contact with a rocky seafloor. According to NASA, Europa could be a promising place to look for life beyond Earth. Europa’s surface is mostly solid water ice, extremely smooth and crisscrossed by fractures. Citation: Rover under-ice prototype may lead to Europa search (2014, June 25) retrieved 18 August 2019 from https://phys.org/news/2014-06-rover-under-ice-prototype-europa.html Explore further © 2014 Phys.org More information: solarsystem.nasa.gov/planets/p … Display=OverviewLongwww.nationalgeographic.com/astrobiology/ That last bit about an untethered vehicle operated through satellite link is a key part of their story. National Geographic described the moment when the engineers knew the satellite could work. “An electronic signal travels from NASA’s Jet Propulsion Lab in Pasadena, California, to a robotic rover clinging to the underside of foot-thick ice on an Alaskan lake. The rover’s spotlight begins to glow.” The milestone involves a quest to develop an unmanned vehicle that may one day plumb the icy reaches of Europa.NASA’s Galileo mission explored the Jupiter system from 1995 to 2003, with flybys of Europa. It obtained the closest images to date of the moon’s fractured surface. Attracting attention were strange pits and domes that suggested ice possibly slowly turning over, or convecting, due to heat from below. Last year, NASA announced evidence from researchers using the Hubble Space Telescope that Europa might be actively venting plumes of water into space. A National Geographic video indicates the NASA effort is interesting not only because of Europa but because of the advances the Jet Propulsion Laboratory team made in developing its early prototype. This, after all, is a roving, untethered vehicle being shown under the Alaskan ice. When the probe reaches Europa, its search for life may be modeled on a trial such as this one. With explanations by astrobiologist Kevin Hand, the video shows testing around the frozen lakes of Barrow, Alaska. The scientists turned to Alaska’s ecosystems where lakes freeze over every year, representative of life in an extreme environment, and helping to guide the NASA team in assessing if a world like Europa could harbor life. They cut a hole in the ice, put the Rover underneath the ice and handed over control to engineers at the Jet Propulsion Laboratory.”So we think this was the first time ever, that an underwater, under-ice, untethered vehicle has been operated through satellite link.” This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.last_img read more

The Hidden Psychology Behind Games of Thrones

first_imgAs Game of Thrones barrels to its conclusion, impatient fans can find torrents of rumors and alleged leaks as to who will rule Westeros when the curtain closes. We will not be linking to these flagrant would-be spoilers, but we can offer proprietary information that spoils nothing: The psychological personality profiles that drive the motivations of the remaining contenders. TIME is currently running a scientifically crafted survey that determines how closely your personality aligns with each of five major characters—Cersei, Daenerys, Tyrion, Arya and Jon Snow. The questions, compiled for TIME by a team of research psychologists, are all drawn from established social and behavioral science and measure your attitudes toward leadership and self-regard. But to pull this off, there was one dataset that we had to collect ourselves: meaningful information on the personalities of the characters themselves. So this project began with a low-profile stage in which devoted fans took our survey on behalf of the five characters, answering each question as they believe the characters would have answered. This phase was conducted before the current season began, so the profiles do not reflect anything that has happened recently, but rather their general tendencies in how they feel and behave. Read the whole story: TIMElast_img read more

A music lovers mission

first_imgIt was sheer curiosity that led to a beautiful serendipity which has now become a mission for author-classical singer Vikram Sampath, who has created an archive of Indian classical music, carnatic music, folk music and speeches from the pre-Independence era, digitised them and built a national treasure online.The Archive of Indian Music(AIM) is a museum of sorts to listen to the golden voices of bygone era. The recordings span 1902 to 1952 and boast of many known and unknown names like Bhimsen Joshi, Devika Rani, Abdul Karim Khan, Hirabai Barodekar and Madurai Mani Iyer among others. It can be accessed at Also Read – ‘Playing Jojo was emotionally exhausting’www.archiveofindianmusic.org.‘I was curious to listen to the voice of legendary singer Gauhar Jaan (the first Indian voice to be recorded in 1902) while I was writing a book on her. It was during the research that I realised there were old gramophone recordings of known and unknown singers in abominable condition,’ Sampath, 33, told in an interview. ‘I started collecting them and reached out to record collectors. Some generous people donated. This is how the process began accidentally. One thing led to the another by chance,’ he said, adding he has around 100,000 records for digitising, of which 10,000 have already been transferred. Also Read – Leslie doing new comedy special with NetflixThe BITS Pilani alumnus has penned three well-researched books on history and music: Splendours of Royal Mysore, My Name is Gauhar Jaan – The life and times of a musician and Voice of the Veena: S. Balachander, a biography.The pilot of the site went online in January. After receiving an overwhelming response from music connoisseurs, the team is now working on making the final version user friendly.There was never any intention of minting money through the site, Sampath said.To sustain and monetise the site, he has plans to create audio-visual exhibitions across India.last_img read more