(Press-News.org) This news release is available in German and German.
Quantum computation, quantum communication and quantum cryptography often require entanglement. For many of these upcoming quantum technologies, entanglement – this hard to grasp, counter-intuitive aspect in the quantum world – is a key ingredient. Therefore, experimental physicists often need to verify entanglement in their systems. "Two years ago, we managed to verify entanglement between up to 14 ions", explains Thomas Monz. He works in the group of Rainer Blatt at the Institute for Experimental Physics, University Innsbruck. This team is still holding the world-record for the largest number of entangled particles. "In order to verify the entanglement, we had to make some, experimentally calibrated, assumptions. However, assumptions, for instance about the number of dimensions of the system or a decent calibration, make any subsequently derived statements vulnerable", explains Monz. Together with Julio Barreiro, who recently moved on the Max Planck Institute of Quantum Optics in Garching, and Jean-Daniel Bancal from the group of Nicolas Gisin at the University of Geneva, now at the Center for Quantum Technologies in Singapore, the physicists derived and implemented a new method to verify entanglement between several objects.
Finding correlations
The presented device-independent method is based on a single assumption: "We only have to make sure that we always apply the same set of operations on the quantum objects, and that the operations are independent of each other", explains Julio Barreiro. "However, which operations we apply in detail – this is something we do not need to know." This approach - called Device Independent - allows them to get around several potential sources of error, and subsequently wrong interpretations of the results. "In the end, we investigate the correlations between the settings and the obtained results. Once the correlations exceed a certain threshold, we know that the objects are entangled." For the experimentally hardly avoidable crosstalk of operations applied to levitating calcium ions in the vacuum chamber in Innsbruck, the Swiss theorist Jean-Daniel Bancal managed to adapt the threshold according to a worst-case scenario. "When this higher threshold is breached, we can claim entanglement in the system with high confidence", states Bancal.
Assumptions as Achilles heel
For physicists, such procedures that are based on very few assumptions are highly interesting. By being basically independent of the system, they provide high confidence and strengthen the results of experimentalists. "Assumptions are always the Achilles heel – be that for lab data or theory work", stresses Thomas Monz. "We managed to reduce the number of assumption to verify entanglement to a minimum. Our method thus allows for reliable statements about the entanglement in a system." In the actual implementation, the physicists in Innsbruck could verify entanglement of up to 6 ions. This new method can also be applied for larger systems. The technical demands, however, also increase accordingly.
INFORMATION:
Publication: Demonstration of genuine multipartite entanglement with device-independent witnesses. Julio T. Barreiro, Jean-Daniel Bancal, Philipp Schindler, Daniel Nigg, Markus Hennrich, Thomas Monz, Nicolas Gisin, and Rainer Blatt. Advance Online Publication, Nature Physics 2013 (DOI: 10.1038/NPHYS2705)
An infallible quantum measurement
2013-08-05
ELSE PRESS RELEASES FROM THIS DATE:
Necrostatin-1 counteracts aluminum's neurotoxic effects
2013-08-05
Amsterdam, NL, August 2, 2013 – Investigators have linked aluminum accumulation in the brain as a possible contributing factor to neurodegenerative disorders such as Alzheimer's disease. A new study published in Restorative Neurology and Neuroscience sheds light on the mechanism underlying aluminum-induced neuronal cell death and identifies necrostatin-1 as a substance which counteracts several of aluminum's neurotoxic effects.
Researchers have long focused on why neurons die in degenerative diseases. One process is apoptosis, a form of gene-directed programmed cell death ...
Putting the brakes on pain
2013-08-05
Neuropathic pain — pain that results from a malfunction in the nervous system — is a daily reality for millions of Americans. Unlike normal pain, it doesn't go away after the stimulus that provoked it ends, and it also behaves in a variety of other unusual and disturbing ways. Someone suffering from neuropathic pain might experience intense discomfort from a light touch, for example, or feel as though he or she were freezing in response to a slight change in temperature.
A major part of the answer to the problem of neuropathic pain, scientists believe, is found in spinal ...
Seeing depth through a single lens
2013-08-05
Researchers at the Harvard School of Engineering and Applied Sciences (SEAS) have developed a way for photographers and microscopists to create a 3D image through a single lens, without moving the camera.
Published in the journal Optics Letters, this improbable-sounding technology relies only on computation and mathematics—no unusual hardware or fancy lenses. The effect is the equivalent of seeing a stereo image with one eye closed.
That's easier said than done, as principal investigator Kenneth B. Crozier, John L. Loeb Associate Professor of the Natural Sciences, explains.
"If ...
Depressed fish could help in the search for new drug treatments
2013-08-05
Chronic stress can lead to depression and anxiety in humans. Scientists working with Herwig Baier, Director at the Max Planck Institute of Neurobiology in Martinsried, recently discovered a very similar correlation in fish. Normally, the stress hormone cortisol helps fish, as in humans, to regulate stress. Fish that lack the receptor for cortisol as a result of a genetic mutation exhibited a consistently high level of stress. They were unable to become accustomed to a new and unfamiliar situation. The fishes' behaviour returned to normal when an antidepressant was added ...
Working-life training and maternity spells are related to slower cognitive decline in later life
2013-08-05
Employment gaps may promote but also reduce cognitive function in older age, as new research from the University of Luxembourg has shown. In particular, some of the findings suggest that leaves reported as unemployment and sickness are associated with higher risk of cognitive impairment indicating that these kinds of employment gaps may decrease cognitive reserve in the long run. Strongest evidence was found for training and maternity spells being related to slower cognitive decline, suggesting beneficial associations of these kinds of leaves on cognitive function.
In ...
LA BioMed researchers find maternal smoking linked to asthma in the third generation
2013-08-05
LOS ANGELES – (August 5, 2013) – With some 300 million people around the world living with asthma, a study by Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center (LA BioMed) researchers that was released ahead-of- print found for the first time that maternal smoking can cause the third generation of offspring to suffer from the chronic lung disease.
The study, published online by the American Journal of Physiology - Lung Cellular and Molecular Physiology, reported that maternal nicotine exposure during pregnancy is linked to asthma in the third generation ...
Eating a big breakfast fights obesity and disease
2013-08-05
Whether you hope to lose weight or just stay healthy, what you eat is a crucial factor. The right nutrients can not only trim your waistline, but also provide energy, improve your mood, and stave off disease. Now a Tel Aviv University researcher has found that it's not just what you eat — but when.
Metabolism is impacted by the body's circadian rhythm – the biological process that the body follows over a 24 hour cycle. So the time of day we eat can have a big impact on the way our bodies process food, says Prof. Daniela Jakubowicz of TAU's Sackler Faculty of Medicine ...
Escape from poverty helps explain diabetes epidemic in the American South
2013-08-05
COLUMBUS, Ohio – The strikingly high prevalence of Type 2 diabetes in the American South can be partially traced to rapid economic growth between 1950 and 1980, new research suggests.
The study tests the "thrifty phenotype" hypothesis, which suggests that if economic conditions present during fetal development improve dramatically during a person's childhood, the prospects of poor health in adulthood increase.
According to the hypothesis, children whose parents endured being poor were unprepared biologically to manage the riches of processed foods and the more sedentary ...
Immune system molecule promotes tumor resistance to anti-angiogenic therapy
2013-08-05
A team of scientists, led by Napoleone Ferrara, MD, has shown for the first time that a signaling protein involved in inflammation also promotes tumor resistance to anti-angiogenic therapy.
The findings by Ferrara – professor of pathology at the University of California, San Diego School of Medicine and senior deputy director for basic science at the UC San Diego Moores Cancer Center – and colleagues at Genentech, a biotechnology firm based in South San Francisco, are published in the August 4 Advance Online Publication of the journal Nature Medicine.
Angiogenesis is ...
Breastfeeding may protect against persistent stuttering
2013-08-05
CHAMPAIGN, Ill. — A study of 47 children who began stuttering at an early age found that those who were breastfed in infancy were more likely to recover from stuttering and return to fluent speech.
The analysis, reported in the Journal of Communication Disorders, found a dose-dependent association between breastfeeding and a child's likelihood of recovering from stuttering, with children who were breastfed longer more likely to recover. Boys, who are disproportionately affected by stuttering, appeared to benefit the most. Boys in the study who breastfed for more than ...