(Press-News.org) No-one likes a know-it-all but we expect to be able to catch them out: someone who acts like they know everything but doesn't can always be tripped up with a well-chosen question. Can't they? Not so. New research in quantum physics has shown that a quantum know-it-all could lack information about a subject as a whole, yet answer almost perfectly any question about the subject's parts. The work is published in Physical Review Letters.
"This is something conceptually very weird," says Stephanie Wehner of the Centre for Quantum Technologies at the National University of Singapore, who derived the theoretical result with PhD student Thomas Vidick at the University of California, Berkeley, United States. It's a new phenomenon to add to the list of philosophical conundrums in quantum physics – as strange as the quantum superposition or the quantum uncertainty principle. But the work also has practical motivation: understanding how information behaves in the quantum context is important in emerging technologies such as quantum cryptography and quantum computation.
To frame the problem, consider the example of someone answering questions about a book they have only half-read. If someone has incomplete knowledge about a book as a whole, one expects to be able to identify the source of their ignorance somewhere in the book's pages.
Wehner and Vidick simplify the situation to a book with two pages. They invite the usual quantum players, Alice and Bob, to collaborate. Alice reads the book and is allowed to give Bob one page's worth of information from it.
If Bob only has classical information, it is always possible to work out what he doesn't know. "We show that classically things are, well, sane" says Wehner. In other words, Bob's ignorance can be exposed. Imagine that Bob is a student trying to cheat in an exam, and the notes from Alice cover half the course. An examiner, having secretly inspected Bob's crib notes, could set questions that Bob couldn't answer.
The craziness comes if Bob gets one page's worth of quantum information from Alice. In this case, the researchers show, there is no-way to pinpoint what information Bob is missing. Challenge Bob, and he can guess either page of the book almost perfectly. An examiner could not expose Bob's ignorance even having seen his notes as long as the questions cover no more than half the course – the total amount of information Bob can recount cannot exceed the size of his notes.
It is an unexpected discovery. Researchers had been trying to prove that quantum ignorance would follow classical intuition and be traceable to ignorance of details, and finding that it isn't raises new questions. "We have observed this effect but we don't really understand where it comes from," says Wehner. An intuitive understanding may be forever out of reach, just as other effects in quantum theory defy mechanistic description. However, Wehner and Vidick have begun to design experimental tests and are already formulating a range of ways to explore this strange new frontier. In this work, they devised a means of encoding the quantum information from two pages into one that gave Bob, the quantum know-it-all, the ability to recount all but one bit of the information on either page (the last bit Bob would have to guess). They plan to test whether other encodings would be equally good.
INFORMATION:
Journal reference: T. Vidick and S. Wehner, "Does Ignorance of the Whole Imply Ignorance of the Parts? Large Violations of Noncontextuality in Quantum Theory", Physical Review Letters 107, 030402 (2011); http://prl.aps.org/abstract/PRL/v107/i3/e030402. A free preprint is available at http://arxiv.org/abs/1011.6448.
For more information, please contact:
Stephanie Wehner
Principal Investigator and Assistant Professor
Centre for Quantum Technologies
National University of Singapore
Email: wehner@comp.nus.edu.sg
Tel: +65 6601 1478
National University of Singapore
A leading global university centred in Asia, the National University of Singapore (NUS) is Singapore's flagship university which offers a global approach to education and research, with a focus on Asian perspectives and expertise.
NUS has 15 faculties and schools across three campus locations in Singapore – Kent Ridge, Bukit Timah and Outram. Its transformative education includes a broad-based curriculum underscored by multi-disciplinary courses and cross-faculty enrichment, as well as special programmes which allow students to realise their potential.
NUS has three Research Centres of Excellence (RCE) and 21 university-level research institutes and centres.
It is also a partner for Singapore's 5th RCE. The University shares a close affiliation with 16 national-level research institutes and centres. Research activities are strategic and robust, and NUS is well-known for its research strengths in engineering, life sciences and biomedicine, social sciences and natural sciences. It also strives to create a supportive and innovative environment to promote creative enterprise within its community. More at www.nus.edu.sg.
Centre for Quantum Technologies at the National University of Singapore
The Centre for Quantum Technologies (CQT) was established as Singapore's inaugural Research Centre of Excellence in December 2007. It brings together quantum physicists and computer scientists to explore the quantum nature of reality and quantum possibilities in information processing. CQT is funded by Singapore's National Research Foundation and Ministry of Education and is hosted by the National University of Singapore (NUS). More at www.quantumlah.org.
END
Seventy per cent of eight-month-old babies have a salt (sodium chloride) intake higher than the recommended UK maximum level, due to being fed salty and processed foods like yeast extract, gravy, baked beans and tinned spaghetti.
Many are also given cows' milk, which has higher levels of salt than breast or formula milk, as their main drink despite recommendations that it should not be used in this way until babies are at least one year old. High levels of salt can damage developing kidneys, give children a taste for salty foods and establish poor eating practices that ...
Alexandria, VA — Tobacco related disease is a primary source of mortality for African American men. Recent studies suggest that "alternative" tobacco products may have supplanted cigarettes as the most common products used by young African Americans, according to new research published in the August 2011 issue of Otolaryngology – Head and Neck Surgery.
While the tobacco-related disease burden is higher in African American adults, prevalence rates of tobacco use among young African American teens are surprisingly lower than those reported for whites. This picture changes ...
Washington, D.C. – Colon cleansing - it's been described as a natural way to enhance well-being, but Georgetown University doctors say there's no evidence to back that claim. In fact, their review of scientific literature, published today in the August issue of The Journal of Family Practice, demonstrates that colon cleansing can cause side effects ranging from cramping to renal failure and death.
The procedure, sometimes called colonic irrigation or colonic hydrotherapy, often involves use of chemicals followed by flushing the colon with water through a tube inserted ...
In an effort to reduce the radiation dose delivered by computed tomography (CT) scans, staff at a community-based hospital developed a comprehensive CT radiation dose reduction program which has allowed them to reduce the radiation dose delivered by CT scans at their facility, according to an article in the August issue of the Journal of the American College of Radiology.
CT is an essential tool for the accurate diagnosis of disease and injury but is associated with radiation doses higher than those of conventional X-ray imaging. Although high doses of radiation are ...
An article in the August issue of the Journal of the American College of Radiology summarizes methods for radiation dose optimization in head computed tomography (CT) scans. Head CT is the second most commonly performed CT examination, with 28 percent of the total number of CT examinations.
Magnetic resonance imaging (MRI) has emerged as the imaging modality of choice for a vast majority of brain and spinal indications. However, CT remains an integral part of modern neuroradiologic practice that can provide lifesaving information about patient management, specifically ...
(CHICAGO) – Current approaches to dietary counseling for obesity are heavily rooted in the notion of personal choice and will power – the ability to choose healthy foods and portion sizes consistent with weight loss while foregoing sweets and comfort foods.
According to preventive medicine and behavioral experts at Rush University Medical Center, research supports a new counseling approach that views obesity as a result of neurobehavioral processes - ways in which the brain controls eating behavior in response to cues in the environment.
The new, proposed neurobehavioral ...
CHAMPAIGN, Ill. — Whatever does not kill a plant may actually make it stronger. After being partially eaten by grazing animals, for example, some plants grow bigger and faster and reproduce more successfully than they otherwise would. In a new study, researchers report that one secret to these plants' post-traumatic triumph lies in their ability to duplicate their chromosomes – again and again – without undergoing cell division.
While this process, called "endoreduplication," is not new to science, no previous study had looked at it in relation to the seemingly miraculous ...
Segun un informe publicado recientemente en la revista Lancet Infectious Diseases, investigadores britanicos han descubierto una nueva bacteria resistente a medicamentos. Estas bacterias han mutado y ahora presentan un nuevo gen--NDM-1--que las convierte en practicamente inmunes por ahora. Esa modificacion genetica altera la composicion organica de las celulas de las bacterias, y les proporciona la capacidad de resistir a los ataques de la mayoria de antibioticos que hay en el mercado actualmente. Al parecer, el NDM-1 afecta a una gran variedad de bacterias, incluida la ...
During the 1970s and 1980s, researchers and policymakers became increasingly worried about multiple consequences of acidic emissions of sulfur dioxide and nitrogen oxides from the stacks of power stations, and eventually they were controlled. In Europe, there was much concern about the effects on Sweden's many lakes, which were found to be in some cases strikingly acidic. The Swedish government instituted a program of countering the acidification by adding thousands of tonnes of lime to the lakes.
The link between emissions and acidification of lakes was never universally ...
Hampton Inn Spartanburg - North I-85, a premier Spartanburg hotel, announces a special deal for their guests to enjoy. From now through September 30, 2011 this Spartanburg SC hotel is offering the Double Your HHonors and Go Further, Faster Package. Travelers can earn Double Points or Double Miles when they book and stay at any of our property or any other participating hotel or resort. To receive the offer Hilton HHonors members must first register at www.HHonors.com/DoubleYourHHonors prior to completing any eligible stay within the Promotion Period. The Double Your HHonors ...
