Physicists Investigate Unusual FourQubit Entanglement

first_img Quantum Communication Over Flawed Networks may be Possible Four-qubit bound entanglement may have applications in secret sharing protocols, such as the secret code used to protect the launch sequence of a nuclear missile. Credit: DOD Defense Visual Information Center. Explore further (PhysOrg.com) — For the first time, physicists have experimentally demonstrated a four-qubit bound-entangled state – a peculiar form of entanglement that cannot be distilled (optimized) by the usual means. However, the scientists have found a novel method for distilling the entanglement by working with two qubits at a time. As the researchers explain, the special properties of bound entanglement could make it a useful quantum resource for new multiparty communication and secret sharing schemes, and the results could also contribute to a deeper understanding of the foundations of quantum mechanics. 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.center_img To create the Smolin state in the laboratory, the scientists used polarized photons as qubits. Using a laser, they pumped two ultraviolet pulses into a nonlinear crystal to create four photons, entangled in pairs. Then, by applying single-polarization-qubit flip and phase gates between one photon from each pair, the scientists created a bound-entangled state that is an equal mixture of all four Bell states of the four photons. The researchers fully characterized the entanglement properties of the Smolin state, including constructing its density matrix using quantum-state tomography.After creating the four-qubit bound-entangled state, the scientists investigated distillation. In general, entanglement distillation is a way to maximize entanglement by overcoming noisy channels. Although a bound-entangled state cannot be distilled by local operators and classical communication, it can be distilled in a different way. “We have experimentally demonstrated the unlocking entanglement protocol where two of the four parties sharing the bound entangled state join and perform a Bell measurement, and then broadcast their measurement results to the other two parties, which will then share a maximally entangled state,” Bourennane said. As the physicists explain, these unusual properties make the Smolin bound-entangled state useful for novel multiparty quantum communication schemes, such as secret sharing, communication complexity reduction, and remote information concentration. “For example, in the secret sharing protocol, the splitting of a secret in a way that a single person is not able to reconstruct it is a common task in information processing and especially high security applications,” Bourennane said. “Suppose, for example, that the launch sequence of a nuclear missile is protected by a secret code. Yet, it should be ensured that a single lunatic alone is not able to activate it, but at least two lunatics are required. Solutions for this problem, and its generalization and variations, are studied in classical cryptography. Such problems are called secret sharing. The aim is to split information, using some mathematical algorithms, and to distribute the resulting pieces to two or more legitimate parties. However, classical communication is susceptible to eavesdropping attacks. As the usage of quantum resources can lead to unconditionally secure communication, protocols introducing quantum cryptography to secret sharing have been proposed. The distribution of the four-qubit bound-entangled Smolin state among four communicating parties allows the information splitting and the eavesdropper protection simultaneously.”More information: Elias Amselem and Mohamed Bourennane. “Experimental four-qubit bound entanglement.” Nature Physics. Published online 23 August 2009. DOI: 10.1038/NPHYS1372Copyright 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: Physicists Investigate Unusual Four-Qubit Entanglement (2009, September 30) retrieved 18 August 2019 from https://phys.org/news/2009-09-physicists-unusual-four-qubit-entanglement.html In their study, physicists Elias Amselem and Mohamed Bourennane of Stockholm University have investigated the counterintuitive puzzles of bound entanglement. While entanglement of two pure states is fairly well understood by physicists, the entanglement of mixed and multipartite (more than two) states, such as bound entanglement, is still under intense research. “Quantum entanglement leads to the most counterintuitive effects in quantum mechanics, and it is of great relevance in advanced quantum information methods and also opens a number of questions about the nature of entanglement itself,” Bourennane told PhysOrg.com. “Until now, there is, in general, no known measure for entanglement for a system of more than two particles; therefore, no one is able to say that a state is more or less entangled than the other. At the same time, it is still quite difficult to observe multi-particle entanglement.” As Bourennane explained, inevitable interactions with the environment can cause quantum entanglement to become noisy during the information processing. An important and crucial question is to know which of the noisy states can be distilled to maximally entangled states, with the help of local operations and classical communication, and then be useful again for further information processing. For this reason, the theoretical discovery of bound entanglement (by Ryszard Horodecki, Michal Horodecki and Pawel Horodecki) is very important, being a class of quantum entangled states where no entanglement can be distilled.“Our paper reports for the first time on the experimental evidence of the existence of the bound entangled state, the so-called Smolin state, and fully characterizes it using quantum state tomography,” Bourennane said. “We also study its entanglement properties, using the separability criterion, the Bell inequality, and the witness method. As can be seen, the paper contains new achievements and new insight regarding the general understanding of entanglement.”last_img read more

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Meerkats have ability to distinguish different voices

first_img Citation: Meerkats have ability to distinguish different voices (2011, October 13) retrieved 18 August 2019 from https://phys.org/news/2011-10-meerkats-ability-distinguish-voices.html The new study, led by Dr. Simon Townsend from the University of Zurich, looked at a group of wild meerkats living in the Kalahari Desert in South Africa. To test the possibility of vocal recognition, they conducted an experiment using simple audio playback.In the meerkats foraging areas, the researchers placed two audio speakers to play recordings of the staccato calls that the meerkats make while foraging. It is believed that these calls work to keep the group of foraging animals together and let each other know an individual’s location.They began by playing a call from one of the members of the group from one speaker. They repeated this later with another member’s voice from the other speaker. But it was the next part of the experiment that drew the awareness of the meerkats. The call of one meerkat was played from the first speaker and within seconds was played from the other speaker on the other side of the foraging area.This caused the foraging meerkats to stop what they were doing. As if they knew that something was wrong. They were able to identify that there was no way the same voice could be coming from two different locations. This shows the researchers that while the calls made by the animals are similar, the tone and voice of each meerkat is different and the animals are able to identify the difference.This study was the first to demonstrate vocal recognition in a non-primate animal species and the researchers note that this ability may be more widespread than originally thought, especially in animals that live in social groups. Meerkat. Taken in Victoria, Australia in February 2009. Image: Fir0002/Flagstaffotos. Under GNU Free Documentation License. via Wikipedia. Explore further (PhysOrg.com) — Vocal recognition is widespread in primates but a new study, published in Biology Letters, provides evidence that it may not be limited to humans and primates. The ability to recognize the voice of another may be more widespread in the animal community than previously thought. 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. © 2011 PhysOrg.com Tradition explains why some meerkats are late risers More information: A simple test of vocal individual recognition in wild meerkats, Biology Letters, Published online before print October 12, 2011, doi:10.1098/rsbl.2011.0844AbstractIndividual recognition is thought to be a crucial ability facilitating the evolution of animal societies. Given its central importance, much research has addressed the extent of this capacity across the animal kingdom. Recognition of individuals vocally has received particular attention due, in part, to the insights it provides regarding the cognitive processes that underlie this skill. While much work has focused on vocal individual recognition in primates, there is currently very little data showing comparable skills in non-primate mammals under natural conditions. This may be because non-primate mammal societies do not provide obvious contexts in which vocal individual recognition can be rigorously tested. We addressed this gap in understanding by designing an experimental paradigm to test for individual recognition in meerkats (Suricata suricatta) without having to rely on naturally occurring social contexts. Results suggest that when confronted with a physically impossible scenario—the presence of the same conspecific meerkat in two different places—subjects responded more strongly than during the control, a physically possible setup. We argue that this provides the first clear evidence for vocal individual recognition in wild non-primate mammals and hope that this novel experimental design will allow more systematic cross-species comparisons of individual recognition under natural settings.last_img read more

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Heat from global warming captured by the Pacific Ocean being transferred to

first_img(Phys.org)—A team of researchers working in the U.S. has found what they believe to be the answer to the question of what happened to the heat uptake in the Pacific Ocean due to global warming. In their paper published in Nature Geoscience, they suggest that it has been transferred to the Indian Ocean. Jérôme Vialard with Université Sorbonne offers a News & Views piece on the work done by the team in the same journal issue. Pacific trade winds stall global surface warming—for now Explore further Illustration of increased trade winds in the Pacific and Indian Oceans during the recent warming hiatus, which increased the inter-ocean pressure gradient and thus enhanced Indonesian throughflow. This resulted in an abrupt increase of Indian Ocean heat content. Credit: Sang-Ki Lee Citation: Heat from global warming captured by the Pacific Ocean being transferred to Indian Ocean (2015, May 19) retrieved 18 August 2019 from https://phys.org/news/2015-05-global-captured-pacific-ocean-indian.html Journal information: Nature Geosciencecenter_img © 2015 Phys.org More information: Pacific origin of the abrupt increase in Indian Ocean heat content during the warming hiatus, Nature Geoscience (2015) DOI: 10.1038/ngeo2438AbstractGlobal mean surface warming has stalled since the end of the twentieth century, but the net radiation imbalance at the top of the atmosphere continues to suggest an increasingly warming planet. This apparent contradiction has been reconciled by an anomalous heat flux into the ocean, induced by a shift towards a La Niña-like state with cold sea surface temperatures in the eastern tropical Pacific over the past decade or so. A significant portion of the heat missing from the atmosphere is therefore expected to be stored in the Pacific Ocean. However, in situ hydrographic records indicate that Pacific Ocean heat content has been decreasing9. Here, we analyse observations along with simulations from a global ocean–sea ice model to track the pathway of heat. We find that the enhanced heat uptake by the Pacific Ocean has been compensated by an increased heat transport from the Pacific Ocean to the Indian Ocean, carried by the Indonesian throughflow. As a result, Indian Ocean heat content has increased abruptly, which accounts for more than 70% of the global ocean heat gain in the upper 700 m during the past decade. We conclude that the Indian Ocean has become increasingly important in modulating global climate variability. Most scientists now agree that planet Earth is experiencing global warming, and has been for several decades—most also agree that the cause is an influx of carbon dioxide from human activities. But recent reports that global surface temperatures stopped rising over the past ten to fifteen years, has caused some to become skeptical of the whole idea, even as many scientists have suggested that the surface temperature plateau has been caused by the worlds’ oceans serving as a giant heat sink. The problem with that argument though, has been lack of data suggesting that the biggest of our oceans, the Pacific, has seen a temperature increase. In this new effort, the researchers believe they have found out why.In studying ocean temperature data provided by NOAA covering the past several decades, the researchers found that surface temperatures for the Pacific actually decreased over the past ten years. Recognizing that the heat had to go somewhere, the researchers input the data into models that have been built to show global temperatures, wind movement and other meteorological data. The model showed heat building up in the western Pacific and then being carried by easterly trade winds through the Indonesian archipelago. Upon closer inspection, the team found that surface temperatures (down to 700 meters) in the Indian Ocean had in fact increased to the point that it could account for approximately 70 percent of the heat taken up by the atmosphere over the past decade.The finding by the team appears to be both good and bad news. The good news is that it adds credence to global warming theories—the bad news is that it means that it is possible that at some point in the future all that heat in the ocean could be released back into the atmosphere, creating a sudden temperature spike which would almost assuredly cause massive worldwide problems for those of us that caused the problem in the first place. 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

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The Lunchbox stumped not Indias Oscar choice

first_imgIn a decision that is likely to break many hearts, The Lunchbox, the film that won over critics and your average film buffs alike, has not been picked as India’s official pick for the Oscar. Instead, debut feature filmmaker Gyan Correa’s Gujarati film The Good Road has been chosen to represent India in the best foreign film category at the Academy Awards. It is said to be the first Gujarati film to have made it.‘It was a unanimous decision to select The Good Road, which is a movie produced by the National Film Development Corporation,’ renowned filmmaker Goutam Ghose, who headed the selection committee appointed by the Film Federation of India, said. The movie left behind 21 other Oscar contenders, including strong films like The Lunchbox, Bhaag Milkha Bhaag, English Vinglish, Vishwaroopam, among others.last_img read more

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Am happy that festival films are doing well

first_imgAnurag Kashyap said he is happy that the festival films are doing well commercially as well. ‘I think the myth that the festival films don’t work commercially has changed. This myth is thing of the past now its good the audience has changed and the credit goes to the audience,’ Kashyap said at the 16th MAMI film festival where he presented his Black Friday. Directed by Kashyap, Black Friday featured Kay Kay Menon, Nawazuddin Siddiqui among others.last_img

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Eminent economist and former LF minister Ashok Mitra dead

first_imgKolkata: Noted scholar and former finance minister of the Left Front government in West Bengal, Ashok Mitra, today passed away in a city hospital. He was 90 and his wife had passed away 10 years ago.Mitra was admitted in the hospital almost a month back with complaints of diarrhoea and later developed respiratory problems.A prolific writer of several books, Mitra, also an eminent economist, penned several columns in newspapers on social and economic issues.He was appointed as the finance minister in the Left Front rule and held the portfolio from 1977 to 1987.Prior to that, he was the Chief Economic Adviser to the Central government from 1970 to 1972.last_img read more

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Politics to poetry

first_imgPolitics and films seldom mix, however in one of the firsts for the Indian film fraternity, Former Union Minister and a vibrant literary enterprise in his leisure time, Kapil Sibal has penned yet another 5 beautiful numbers including an item song and a Qawwali for a commercial gripping romantic political Bollywood potboiler that will hit theatres this year end apart from marking his debut as a Bollywood lyricist for the aforesaid film.On Saturday evening, the capital was witness to a gathering of friends, family and fans of the very illustrious and multi-faceted lawyer-politician, when his latest B-town venture, Zainab- A Celebration Of Humanity, was announced with much fanfare in the city in the presence of Jimmy Shergill, Lalit Pandit, and others.  Jay Bhanushali seamlessly conducted the discussion and anchored the event which was hosted for a selective gathering at Imperial Hotel, in the Capital. The event encompassed an item song showcase and unveiling of the film poster.last_img read more

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Anderson takes six as Australia skittled for 136

first_imgEngland bowler James Anderson ripped shellshocked Australia to shreds with six wickets to bowl the tourists out for a paltry 136 on the first day of the third Ashes Test at Edgbaston on Wednesday. Anderson took six for 47 and fellow quicks Stuart Broad and Steven Finn, on his Test return after a two-year absence, two apiece as rejuvenated England put their heavy second Test defeat at Lord’s firmly behind them. Only plucky opener Chris Rogers, passed fit after suffering dizzy spells at Lord’s, offered resistance with a half-century for Australia who failed to cope with the seam and swing-friendly conditions after winning the toss and batting first.  Also Read – Khel Ratna for Deepa and Bajrang, Arjuna for JadejaRogers was eighth man out for 52, lbw to Broad, and Anderson fittingly took the final wicket when Nathan Lyon played on as Australia were dismissed in just 36.4 overs. Anderson, who went wicketless in London where Australia squared the series with a 405-run victory after losing the opener in Cardiff, took four wickets in 19 balls after lunch. His quickfire burst started when he had Adam Voges caught behind for 16. Mitchell Marsh (0) also nicked a swinging delivery to Jos Buttler and then Peter Nevill’s bad misjudgement saw him bowled for two without offering a shot.  Also Read – Endeavour is to facilitate smooth transition: ShastriEngland’s leading wicket-taker in Tests then bagged his 18th five-wicket haul when Mitchell Johnson (3) sliced to Ben Stokes at fifth slip. Australia lost three wickets in a rain-interupted morning with Finn, branded “unselectable” by former England limited overs coach Ashley Giles 18 months ago due to a breakdown in his bowling action, took the scalps of Steve Smith (7) and skipper Michael Clarke (10).  After Anderson had given England a flying start by trapping David Warner (2) lbw, Finn, recalled in place of an unfit Mark Wood, found bounce and movement on the quickest pitch of the series so far.last_img read more

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Govt points finger at Metro Railway over fire in rake Fire department

first_imgKolkata: The state government has blamed Metro Railway for the incident of fire that took place on Thursday in an air-conditioned rake near Maidan station.On Friday, a meeting was held at Kolkata Police headquarter Lalbazar with state Fire minister Sujit Bose, officials from Kolkata Police and officials from the Fire department, where it was decided that Metro Railway will be issued a notice in connection with the incident. If any flaw or negligence is found on their part, action will be taken accordingly. Also Read – Rain batters Kolkata, cripples normal lifeAccording to sources, a high-level inquiry has already been ordered by the Metro Railway in this regard. However, the Fire department will also inquire about the matter. Metro Railway will be asked to furnish details of the fire safety management system installed in the rakes. They have also been asked to inspect the passenger safety systems which should be maintained strictly. Bose alleged on Friday that the incident has happened due to the negligence of Metro Railway. He said: “No one can deny the fact that there was negligence on part of Kolkata Metro. It needs to be looked into.” Also Read – Speeding Jaguar crashes into Mercedes car in Kolkata, 2 pedestrians killedThe Director General (DG) of Fire Jag Mohan stated that after Metro Railway provides them the necessary information mentioned in the notice, the Fire department will probe the matter. Fire department officials may also check the fire safety management system to make sure that the installed machineries are in working condition. “We are going to issue a notice to Metro Railway asking for the fire safety and life safety system details. After getting the details we will probe whether the systems are working properly or not. If any irregularity is noticed then action will be taken accordingly,” said the DG. During the fire on Thursday, several passengers had alleged that the motorman of the rake had locked the door between the passenger coach and the motorman’s cabin and left the rake. According to Metro Railway guideline, in case of an emergency passengers should be evacuated using the front door of the motorman’s cabin. But on Thursday, passengers were evacuated using the motorman’s entry as there was no ladder which could be used at the front door. Though Metro authorities claimed that the rescue operation was started within 20 minutes, passengers stated that the claim is not true. They were evacuated by the police personnel. Before the arrival of police, a few passengers had managed to break the window glasses to get out of the coach which was on fire. Apart from Thursday’s incident, police and Fire department officials also discussed about taking steps for better coordination between the police and Fire department during emergency situations. It was also mentioned that during a distress call, fire tenders should be given free passage to reach the incident spot as early as possible. On Thursday, Metro Railway passengers faced a tremendous ordeal after fire broke out inside an air-conditioned rake of a Dum Dum bound train just before entering Maidan station at around 5 pm. Smoke was detected inside the compartment just next to the motorman’s cabin, soon after the train left Rabindra Sadan. The train came to a halt inside the tunnel at a distance of around 50 metres from Maidan station. A number of passengers were injured and were admitted at SSKM Hospital.last_img read more

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Cricket betting racket busted in Kolkata 4 arrested

first_imgKolkata: The Kolkata Police Thursday claimed to have busted a cricket-betting racket in the city by arresting four people and seizing over Rs 1 crore from them. Acting on a tip-off, a team of Detective Department officers conducted raids at 12 places in the city, a senior officer said. The money was seized from four places under Burrabazar Police Station and Posta Police Station area, he said, adding that four people have been arrested so far. “Raids are still being conducted at different places under Bowbazar, Jorabagan, Burrabazar and Posta Police Station areas,” he said.last_img read more

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