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Quantum Cat's 'Whiskers' Thursday, May 14, 2009 - Anuradha Menon Home >> News >> Physics   
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Researchers from Oxford University have turned the tables on the degrading receptiveness of quantum entangled systems. Conventional quantum sensors suffer from interference from their environment, but this novel version harnesses this sensitivity to measure incredibly weak magnetic fields. This new technology could be easily applied in areas such as geological surveying.
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The experiment revolves around a cat placed in a sealed box with radioactive material, a Geiger counter, and a bottle of poison. When the Geiger counter senses the decay of the radioactive material, a mechanism breaks the bottle of poison and kills the cat. All of this might sound gruesome, but it makes the remarkable prediction that until the box is opened the cat is both alive and dead. Since the cat was placed in a sealed box and cannot be viewed, the cat exists in an unknowable state. However, the team at Oxford dealt with a relative “quantum cat,” which is a molecule of trimethlyphosphite (TMP). In this case, the state of the molecule’s nuclear spin was either “up” or “down.” To create the “quantum cat” the researchers used a star-shaped molecule which had a central atom and nine surrounding atoms. Radio frequency was then applied to the molecule to place it in an entangled state where all ten spins are spinning one way (“alive”) and the other way (“dead”) at the same time. Dr. John Morton of Oxford University’s Department of Materials said, “We found that compared to a non-entangled system our cat was many times more sensitive to the presence of a very weak magnetic field.” The team hopes to extend the project to examine how quantum sensors based on the “quantum cat” could be combined with existing sensors based on magnetic resonance and to create a real world application based on their findings. Such sensors could be utilized on the ocean floor to detect minute fluctuations in Earth’s magnetic field which could indicate untapped reserves of gas or oil. TFOT has previously written about a research dealing with superimposed quantum dots, which are able to ‘trap’ single electrons, Be also sure to check out our coverage of a study, in which researchers succeeded to control the quantum state of a single electron by placing the electron in two places at once. You can also check out our video on “Flatland” – a theoretical world where the concept of “up” or “down” doesn’t exist. Additional information on the “quantum cat” can be obtained at Oxford’s website, while information on the famous “Schrodinger’s Cat” experiment can be found here. |
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I\'m not clear how the cat and other (pet friendly) related experiments can distinguish between entangled particles that have a random yet pre-chosen state (you just don\'t know it until you check it, thus the \"remote\" particle had that state all along as well) and having one particle\'s state determination actually influence the remote particles state. What makes them sure the states were not pre-determined and just not detectable by any method we know of? Or am I missing something here? (which is certainly very possible!) |
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Hi Andrew, The technique we use is fairly simple. We prepared the system in an initially known state, and then measured how that state had changed after exposure to an unknown field. Because we knew the initial state, and from the measurements gained some knowledge of the final state, we could infer the unknown field strength. What we believe makes our results interesting is that by using an entangled quantum state, the accuracy to which we can determine the unknown field is increased. The basic idea is that by using cat states of N particles it is possible to pick up phase N times faster than with unentangled states. If the spins are not entangled then certainly we have more spins to use, but the uncertainty scales as one over the square root of N (simply from probability theory), rather than as one over N as it does for the entangled states, so there is a net gain from using entangled states. A full calculation can be found in our paper. Hope this helps answer your question, Joe |
