Bell correlations measured in half a million atoms

first_imgIllustration of a squeezed spin state used to demonstrate Bell correlations. Credit: Engelsen et al. ©2017 American Physical Society Natural systems show nonlocal correlations Citation: Bell correlations measured in half a million atoms (2017, April 17) retrieved 18 August 2019 from https://phys.org/news/2017-04-bell-million-atoms.html Journal information: Physical Review Letters The researchers, led by Mark Kasevich at Stanford University, have published a paper on the large system exhibiting Bell-type quantum correlations in a recent issue of Physical Review Letters.”Our results illustrate the richness of quantum many-body states involving many entangled systems,” Kasevich told Phys.org. “Little is known at this frontier.”In order to use quantum correlations for practical purposes, the correlations must be measured. Until recently, the only way to measure Bell correlations in a system of atoms (or other components) was to measure the correlations between all of the individual atoms. But a few years ago, physicists developed a new method of measuring Bell correlations that does not require measuring individual components, but can be done by measuring the collective properties of the system as a whole. Last year, scientists used this method to demonstrate Bell correlations in a Bose-Einstein condensate of around 500 atoms.In the new study, the researchers have increased this number to a record 500,000 atoms. To do this, they used a method called spin squeezing, in which they started by preparing all of the atoms’ spins in a superposition of up and down states. The researchers then reduced (or “squeezed”) the uncertainty of one spin component below the value allowed for uncorrelated atoms, which simultaneously increases the uncertainty of the conjugate spin component to satisfy the uncertainty principle. By making collective measurements on the spin properties of the entire system, the researchers demonstrated that the spin states exhibit correlations beyond what is expected by classical physics. Currently, it’s unclear exactly how nonlocal Bell correlations may be used in such large systems. In smaller systems, Bell correlations have been used to generate random numbers, which have applications in cryptography. The physicists also expect that the experimental methods used here could be used to test the predictions of quantum theory.”We hope to test quantum mechanics in news ways with spatially extended versions of the states used in this work,” Kasevich said. “Imagine a quantum many-body state extending over one meter involving thousands of correlated particles. The squeezed states used for this work also have practical application in sensors, as they can be exploited to reduce sensor noise.” More information: Nils J. Engelsen, Rajiv Krishnakumar, Onur Hosten, and Mark A. Kasevich. “Bell Correlations in Spin-Squeezed States of 500 000 Atoms.” Physical Review Letters. DOI: 10.1103/PhysRevLett.118.140401center_img (Phys.org)—Physicists have demonstrated Bell correlations in the largest physical system to date—an ensemble of half a million atoms at an ultracold temperature of 25 µK. The presence of Bell correlations indicates that all of the atoms share nonlocal quantum correlations with each other. These correlations could one day be used in quantum information systems and to design new tests of quantum mechanics. © 2017 Phys.org Explore further 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

Trend Alert Crop it

first_imgReplay the Lucky Song by Madonna that caused a controversy about ‘crop tops’; newly known as the midriff exposure, is simply rewinding the 80s style. From pop artists to television celebs to super stars, all are in saga with showing off their taut tummies. Some of the artists sporting the crop top look include Rihanna, Frieda Pinto, Sonam Kapoor and Hilary Rhod.For Indian’s, crop top is the next step forward from the typical traditional wear ‘choli’. A few ways to style the crop top right are: Also Read – ‘Playing Jojo was emotionally exhausting’Team the crop top with high-waist jeans, shorts or skirts, so you reveal less but still look stylish.  Go flirty with tying a shirt up at the front with a high waist skirt or jeans.  For those chicas who like to play safe, team your crop top with a fitted tank underneath andgo trendy. You can also go formal by teaming the midriff with snazzy pants and a groovy jacket. Beat the heat with these and add the gaga to your daily parade. As the crop top is topping the field all the way, a few curated pieces can be found at a clothing website called Miss Chase (http://www.misschase.com). A UK fashion brand made affordable for the first time ever.  Just flaunt it if you have it! Now’s a good time to tone that tummy and pick a colour and cut that works for you – and you will be all set to make heads turn.last_img read more

Exhibition brings out lyricism in sculptor Dhanrajs work

first_imgA retrospective exhibition highlighting the musicality in Indian sculptor Dhanraj Bhagat’s work, is being showcased at the National Gallery of Modern Art (NGMA) here.The exhibition titled “Dhanraj Bhagat (1917-1988): Journey from the Physical to the Spiritual” has over 400 works on display, including sketches and sculptures. “Bhagat evoked brilliantly the inner music in his take on the iconic Nataraja or Dancing Shiva, in the elongated lyrical limbs of the lord as though swaying in the tune of the music,” NGMA said in a statement. Also Read – Add new books to your shelfMusic also translates in his flowing sketches of women and musicians with almost ethereal quality, it added.Born in Lahore in 1917, Bhagat, in his earlier depictions showed rural men and women involved in daily activities, inspired by what he saw around him.He later joined the Mayo School of Art, and served as the head of the sculpture department at the College of Art, New Delhi for three decades.The 1977, Padma Shri awardee, worked with mediums like clay, wood, metal or cement, and seemed to have introduced to his work a certain lyrical form. Also Read – Over 2 hours screen time daily will make your kids impulsiveBhagat’s style of sculpting romanticism in an objective subject took a spiritual turn in his later years. As his works began to be dominated by a minimalist geometry through which he formed strong images of monarchs, gods and celestial beings, he rendered a spiritual touch to his work.The exhibition seeks to capture the moods and styles of the artist from his initial years to the later simplified geometric forms and icons.The extensive retrospective exhibition marks the sculptor’s centenary year, and is now on display in Mumbai till August 14.last_img read more

Google and Facebook working hard to clean image after the media backlash

first_imgLast Friday’s uncontrolled spread of horrific videos on the Christchurch mosque attack and a propaganda coup for espousing hateful ideologies raised questions about social media. The tech companies scrambled to take action on time due to the speed and volume of content which was uploaded, reuploaded and shared by the users worldwide. In Washington and Silicon Valley, the incident crystallized growing concerns about the extent to which government and market forces have failed to check the power of social media. The failure highlighted the social media companies struggle to police content that are massively lucrative and persistently vulnerable to outside manipulation despite years of promises to do better. After the white supremacist live-streamed the attack and uploaded the video to Facebook, Twitter, YouTube, and other platforms across the internet. These tech companies faced back lashes from the media and internet users worldwide, to an extent where they were regarded as complicit in promoting white supremacism too. In response to the backlash, Google and Facebook provides status report on what they went through when the video was reported, the kind of challenges they faced and what are the next steps to combat such incidents in future. Google’s report so far… Google in an email to Motherboard says it employs 10,000 people across to moderate the company’s platforms and products. They also described a process they would follow when a user reports a piece of potentially violating content—such as the attack video; which is The user flagged report will go to a human moderator to assess. The moderator is instructed to flag all pieces of content related to the attack as “Terrorist Content,” including full-length or sections of the manifesto. Because of the document’s length the email tells moderators not to spend an extensive amount of time trying to confirm whether a piece of content does contain part of the manifesto. Instead, if the moderator is unsure, they should err on the side of caution and still label the content as “Terrorist Content,” which will then be reviewed by a second moderator. The second moderator is told to take time to verify that it is a piece of the manifesto, and appropriately mark the content as terrorism no matter how long or short the section may be. Moderators are told to mark the manifesto or video as terrorism content unless there is an Educational, Documentary, Scientific, or Artistic (EDSA) context to it. Further Google adds that they want to preserve journalistic or educational coverage of the event, but does not want to allow the video or manifesto itself to spread throughout the company’s services without additional context. Google at some point had taken the unusual step of automatically rejecting any footage of violence from the attack video, cutting out the process of a human determining the context of the clip. If, say, a news organization was impacted by this change, the outlet could appeal the decision, Google commented. “We made the call to basically err on the side of machine intelligence, as opposed to waiting for human review,” YouTube’s Product Officer Neal Mohan told the Washington Post in an article published Monday. Google also tweaked the search function to show results from authoritative news sources. It suspended the ability to search for clips by upload date, making it harder for people to find copies of the attack footage. “Since Friday’s horrific tragedy, we’ve removed tens of thousands of videos and terminated hundreds of accounts created to promote or glorify the shooter,” a YouTube spokesperson said. “Our teams are continuing to work around the clock to prevent violent and graphic content from spreading, we know there is much more work to do,” the statement added. Facebook’s update so far… Facebook on Wednesday also shared an update on how they have been working with the New Zealand Police to support their investigation. It provided additional information on how their products were used to circulate videos and how they plan to improve them. So far Facebook has provided the following information: The video was viewed fewer than 200 times during the live broadcast. No users reported the video during the live broadcast. Including the views during the live broadcast, the video was viewed about 4,000 times in total before being removed from Facebook. Before Facebook was alerted to the video, a user on 8chan posted a link to a copy of the video on a file-sharing site. The first user report on the original video came in 29 minutes after the video started, and 12 minutes after the live broadcast ended. In the first 24 hours, Facebook removed more than 1.2 million videos of the attack at upload, which were therefore prevented from being seen on our services. Approximately 300,000 additional copies were removed after they were posted. As there were questions asked to Facebook about why artificial intelligence ( AI) didn’t detect the video automatically. Facebook says AI has made massive progress over the years to proactively detect the vast majority of the content it can remove. But it’s not perfect. “To achieve that we will need to provide our systems with large volumes of data of this specific kind of content, something which is difficult as these events are thankfully rare.” says Guy Rosen VP Product Management at Facebook. Guy further adds, “AI is an incredibly important part of our fight against terrorist content on our platforms, and while its effectiveness continues to improve, it is never going to be perfect. People will continue to be part of the equation, whether it’s the people on our team who review content, or people who use our services and report content to us. That’s why last year Facebook more than doubled the number of people working on safety and security to over 30,000 people, including about 15,000 content reviewers to report content that they find disturbing.” Facebook further plans to: Improve the image and video matching technology so that they can stop the spread of viral videos of such nature, regardless of how they were originally produced. React faster to this kind of content on a live streamed video. Continue to combat hate speech of all kinds on their platform. Expand industry collaboration through the Global Internet Forum to Counter Terrorism (GIFCT). Challenges Google and Facebook faced to report the video content According to Motherboard, Google saw an unprecedented number of attempts to post footage from the attack, sometimes as fast as a piece of content per second. But the challenge they faced was to block access to the killer’s so-called manifesto, a 74-page document that spouted racist views and explicit calls for violence. Google described the difficulties of moderating the manifesto, pointing to its length and the issue of users sharing the snippets of the manifesto that Google’s content moderators may not immediately recognise. “The manifesto will be particularly challenging to enforce against given the length of the document and that you may see various segments of various lengths within the content you are reviewing,” says Google. A source with knowledge of Google’s strategy for moderating the New Zealand attack material said this can complicate moderation efforts because some outlets did use parts of the video and manifesto. UK newspaper The Daily Mail let readers download the terrorist’s manifesto directly from the paper’s own website, and Sky News Australia aired parts of the attack footage, BuzzFeed News reported. On the other hand Facebook faces a challenge to automatically discern such content from visually similar, innocuous content. For example if thousands of videos from live-streamed video games are flagged by the systems, reviewers could miss the important real-world videos where they could alert first responders to get help on the ground. Another challenge for Facebook is similar to what Google faces, which is the proliferation of many different variants of videos makes it difficult for the image and video matching technology to prevent spreading further. Facebook found that a core community of bad actors working together to continually re-upload edited versions of the video in ways designed to defeat their detection. Second, a broader set of people distributed the video and unintentionally made it harder to match copies. Websites and pages, eager to get attention from people seeking out the video, re-cut and re-recorded the video into various formats. In total, Facebook found and blocked over 800 visually-distinct variants of the video that were circulating. Both companies seem to be working hard to improve their products and gain user’s trust and confidence back. Read Next How social media enabled and amplified the Christchurch terrorist attack Google to be the founding member of CDF (Continuous Delivery Foundation) Google announces the stable release of Android Jetpack Navigationlast_img read more