(Press-News.org) This press release is available in German.
Physicists of the group of Prof. Anton Zeilinger at the Institute for Quantum Optics and Quantum Information (IQOQI), the University of Vienna, and the Vienna Center for Quantum Science and Technology (VCQ) have, for the first time, demonstrated in an experiment that the decision whether two particles were in an entangled or in a separable quantum state can be made even after these particles have been measured and may no longer exist. Their results will be published this week in the journal "Nature Physics".
Entangled States
According to the Austrian physicist Erwin Schrödinger, entanglement is the characteristic trait of quantum mechanics. In addition to its crucial role for the foundations of physics, entanglement is also a key resource for upcoming quantum information technologies such as quantum cryptography and quantum computation. Entangled particles exhibit correlations which are stronger and more intricate than those allowed by the laws of classical physics. If two particles are in an entangled quantum state, they have perfectly defined joint properties at the expense of losing their individual properties. This is like having two dice which have no orientation until they are subject to measurement, upon which they certainly show the same (random) side up. In contrast, so-called separable quantum states allow for a classical description, because every particle has well-defined properties on its own. Two dice, each one of them with its own well-defined orientation, are in a separable state. Now, one would think that at least the nature of the quantum state must be an objective fact of reality. Either the dice are entangled or not. Zeilinger's team has now demonstrated in an experiment that this is not always the case.
Exciting realization of a "Gedankenexperiment"
The authors experimentally realized a "Gedankenexperiment" called "delayed-choice entanglement swapping", formulated by Asher Peres in the year 2000. Two pairs of entangled photons are produced, and one photon from each pair is sent to a party called Victor. Of the two remaining photons, one photon is sent to the party Alice and one is sent to the party Bob. Victor can now choose between two kinds of measurements. If he decides to measure his two photons in a way such that they are forced to be in an entangled state, then also Alice's and Bob's photon pair becomes entangled. If Victor chooses to measure his particles individually, Alice's and Bob's photon pair ends up in a separable state. Modern quantum optics technology allowed the team to delay Victor's choice and measurement with respect to the measurements which Alice and Bob perform on their photons. "We found that whether Alice's and Bob's photons are entangled and show quantum correlations or are separable and show classical correlations can be decided after they have been measured", explains Xiao-song Ma, lead author of the study.
According to the famous words of Albert Einstein, the effects of quantum entanglement appear as "spooky action at a distance". The recent experiment has gone one remarkable step further. "Within a naïve classical word view, quantum mechanics can even mimic an influence of future actions on past events", says Anton Zeilinger.
INFORMATION:
Publication in "Nature Physics":
Experimental delayed-choice entanglement swapping: Xiao-song Ma, Stefan Zotter, Johannes Kofler, Rupert Ursin, Thomas Jennewein, Časlav Brukner, and Anton Zeilinger. Nature Physics (2012)
DOI: 10.1038/NPHYS2294.
Quantum physics mimics spooky action into the past
2012-04-24
[Attachments] See images for this press release:
ELSE PRESS RELEASES FROM THIS DATE:
Fish larvae find the reef by orienting: The earlier the better
2012-04-24
MIAMI – The behavior of marine larvae is central to fully understanding and modeling the pelagic (open ocean) stage for many coastal organisms. For the first time, a numerical study conducted by the University of Miami (UM) incorporates horizontal larval fish navigation skills into realistic 3D flow fields, creating a powerful tool that spells out how larvae use environmental cues to find their way back to the reef after being out on the open ocean. The new model uses reliable larval swimming speeds and vertical migration, known life history traits and spawning time to ...
Collaborative research examines executive turnover in federal workplaces
2012-04-24
A research partnership represented by the University of Cincinnati, Cincinnati Children's Hospital Medical Center and the Veterans Health Administration (VHA) National Center for Organization Development (NCOD) is examining factors predicting the turnover of senior executives in the federal workplace. It's an area that has not been widely researched, yet it can result in a costly toll on organizations – both financially in replacing senior staff as well as professionally in the loss of the knowledge, skills and strategy-building talent of senior-level management. The project ...
Pain relief with PAP injections may last 100 times longer than a traditional acupuncture treatment
2012-04-24
CHAPEL HILL, N.C. – Scientists at the University of North Carolina at Chapel Hill have identified a new way to deliver long-lasting pain relief through an ancient medical practice.
In an article published in the April 23 online edition of Molecular Pain, UNC researchers describe how exploiting the molecular mechanism behind acupuncture resulted in six-day pain relief in animal models. They call this new therapeutic approach PAPupuncture.
Principal investigator Mark J. Zylka, PhD, associate professor in the Department of Cell and Molecular Physiology and the UNC ...
Vitamin E in diet protects against many cancers
2012-04-24
Next time you need to choose between vegetable oil and margarine in that favorite recipe, think about your health and reach for the oil.
While the question of whether vitamin E prevents or promotes cancer has been widely debated in scientific journals and in the news media, scientists at the Center for Cancer Prevention Research, at Rutgers Mario School of Pharmacy, and the Cancer Institute of New Jersey, believe that two forms of vitamin E – gamma and delta-tocopherols – found in soybean, canola and corn oils as well as nuts do prevent colon, lung, breast and prostate ...
Carnegie Mellon fluorescent biosensor reveals mechanism critical to immune system amplification
2012-04-24
PITTSBURGH—Using a new fluorescent biosensor they developed, researchers at Carnegie Mellon University have discovered how a key set of immune cells exchange information during their coordinated assault on invading pathogens. The immune cells, called dendritic cells, are harnessed by cancer vaccines and other therapeutics used to amplify the immune system. The finding, published online March 29 in the journal Angewandte Chemie, marks the first time that scientists have visualized how antigens are transferred in the immune system between dendritic cells.
"Knowing the ...
Coalition petitions FDA to fortify corn masa flour with folic acid
2012-04-24
WASHINGTON, D.C., April 18, 2012 – Serious birth defects of the brain and spine in America's babies, particularly those of Hispanic origin, could be reduced if the nation's corn masa flour products were fortified with the B vitamin folic acid, according to a new petition filed with the U.S. Food and Drug Administration (FDA) by a coalition of six organizations:
Gruma Corporation
Spina Bifida Association
March of Dimes Foundation
American Academy of Pediatrics
Royal DSM N.V.
National Council of La Raza
The ...
Protein prevents DNA damage in the developing brain and might serve as a tumor suppressor
2012-04-24
St. Jude Children's Research Hospital scientists have rewritten the job description of the protein TopBP1 after demonstrating that it guards early brain cells from DNA damage. Such damage might foreshadow later problems, including cancer.
Researchers showed that cells in the developing brain require TopBP1 to prevent DNA strands from breaking as the molecule is copied prior to cell division. Investigators also reported that stem cells and immature cells known as progenitor cells involved at the beginning of brain development are more sensitive to unrepaired DNA damage ...
Laparoscopy reduces the risk of small-bowel obstruction
2012-04-24
Open surgery appears to be associated with an increased risk of small-bowel obstructions compared to laparoscopic procedures. This is shown by a new study at the Sahlgrenska Academy, at the University of Gothenburg, Sweden.
In many cases, the surgical technique is the most important factor when it comes to adhesive small-bowel obstruction, even when taking factors such as age, previous operations and other health conditions into account.
This is shown by a study carried out at the University of Gothenburg's Sahlgrenska Academy, which reviewed 108,141 operations carried ...
Xenotransplantation as a therapy for type 1 diabetes
2012-04-24
Type 1 diabetes is caused by autoimmune destruction of the insulin-producing beta cells. Over 250,000 patients suffer from type 1 diabetes in Germany who are treated with daily insulin injections to maintain glucose metabolism. Replacement of the destroyed beta cells by transplantation of either a complete pancreas organ or isolated human beta cells is the only effective way to cure the disease. However, due to the shortage of organ donors this method can be offered to only few patients. As an alternative approach researchers are exploring xenotransplantation, i.e. transplantation ...
A comparison of 2 home exercises to treat vertigo
2012-04-24
AURORA, Colo. (April 23, 2012) A CU School of Medicine researcher who suffers from benign paroxysmal positional vertigo (BPPV) and had to "fix it" before she could go to work one day was using a maneuver to treat herself that only made her sicker. "So I sat down and thought about it and figured out an alternate way to do it. Then I fixed myself and went in to work" and discovered a new treatment for this type of vertigo.
More than seven million people in the U.S. can expect to have benign paroxysmal positional vertigo, a common vertigo disorder, especially as they ...