What happens when you pop a quantum balloon?April 18, 2008Study in this week's Nature journal finds striking similarities and differences between quantum and classical chaos When a tiny, quantum-scale, hypothetical balloon is popped in a vacuum, do the particles inside spread out all over the place as predicted by classical mechanics" The question is deceptively complex, since quantum particles do not look or act like air molecules in a real balloon. Matter at the infinitesimally small quantum scale is both a wave and a particle, and its location cannot be fixed precisely because measurement alters the system. Now, theoretical physicists at the University of Southern California and the University of Massachusetts Boston have proven a long-standing hypothesis that quantum-scale chaos exists - sort of. Writing in the April 17 edition of Nature, senior author Maxim Olshanii reported that when an observer attempts to measure the energies of particles coming out of a quantum balloon, the interference caused by the attempt throws the system into a final, "relaxed" state analogous to the chaotic scattering of air molecules. The result is the same for any starting arrangement of particles, Olshanii added, since the act of measuring wipes out the differences between varying initial states. "It's enough to know the properties of a single stationary state of definite energy of the system to predict the properties of the thermal equilibrium (the end state)," Olshanii said. The measurement - which must involve interaction between observer and observed, such as light traveling between the two - disrupts the "coherent" state of the system, Olshanii said. In mathematical terms, the resulting interference reveals the final state, which had been hidden in the equations describing the initial state of the system. "The thermal equilibrium is already encoded in an initial state," Olshanii said. "You can see some signatures for the future equilibrium. They were already there but more masked by quantum coherences." The finding holds implications for the emerging fields of quantum computing and quantum information theory, said Paolo Zanardi, an associate professor of physics studying quantum information at USC. In Zanardi's world, researchers want to prevent coherent systems from falling into the chaos of thermal equilibrium. "Finding such 'unthermalizable' states of matter and manipulating them is exactly one of those things that quantum information/computation folks like me would love to do," Zanardi wrote. "Such states would be immune from 'decoherence' (loss of quantum coherence induced by the coupling with environment) that's still the most serious, both conceptually and practically, obstacle between us and viable quantum information processing." Zanardi and a collaborator introduced the notion of "decoherence-free" quantum states in 1997. Researchers such as Zanardi and Daniel Lidar, associate professor of chemistry, among others, have helped make USC a major center for the study of quantum computing. University of Southern California |
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| Related Quantum Current Events and Quantum News Articles Quantum gas microscope offers glimpse of quirky ultracold atoms Physicists at Harvard University have created a quantum gas microscope that can be used to observe single atoms at temperatures so low the particles follow the rules of quantum mechanics, behaving in bizarre ways. Research Continues on Secure, Mobile, Quantum Communications Researcher Dr. David H. Hughes of the Air Force Research Laboratory in Rome, N.Y. is leading a team investigating long-distance, mobile optical links imperative for secure quantum communications capabilities in theater. University of Cincinnati researchers create all-electric spintronics A multidisciplinary team of UC researchers is the first to find an innovative and novel way to control an electron's spin orientation using purely electrical means. Transforming Nanowires Into Nano-Tools Using Cation Exchange Reactions A team of engineers from the University of Pennsylvania has transformed simple nanowires into reconfigurable materials and circuits, demonstrating a novel, self-assembling method for chemically creating nanoscale structures that are not possible to grow or obtain otherwise. NIST physicists turn to radio dial for finer atomic matchmaking Investigating mysterious data in ultracold gases of rubidium atoms, scientists at the Joint Quantum Institute of the National Institute of Standards and Technology (NIST) and the University of Maryland and their collaborators have found that properly tuned radio-frequency waves can influence how much the atoms attract or repel one another, opening up new ways to control their interactions. Making monster waves Rogue waves-giant waves that spring up suddenly and tower over the seas around them-have inspired physicists to look for an analogue in light. Fish vision discovery makes waves in natural selection Emory University researchers have identified the first fish known to have switched from ultraviolet vision to violet vision, or the ability to see blue light. The discovery is also the first example of an animal deleting a molecule to change its visual spectrum. Quantum computer chips now 1 step closer to reality In the quest for smaller, faster computer chips, researchers are increasingly turning to quantum mechanics -- the exotic physics of the small. The problem: the manufacturing techniques required to make quantum devices have been equally exotic. That is, until now. Field experiment on a robust hierarchical metropolitan quantum cryptography network Key Laboratory of Quantum Information (CAS), University of Science and Technology of China has recently demonstrated a metropolitan Quantum Cryptography Network (QCN) for Government Administration in Wuhu, China. Because of its scientific significance and social impact, the project is reported in Volume 54, Issue 17 (September, 2009) of the Chinese Science Bulletin authored by Fang-xing Xu et al. Rutgers physicists discover novel electronic properties in two-dimensional carbon structure Rutgers researchers have discovered novel electronic properties in two-dimensional sheets of carbon atoms called graphene that could one day be the heart of speedy and powerful electronic devices. More Quantum Current Events and Quantum News Articles |
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