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## Historically, Caltech physics has focused on the most fundamental problems, su

Hillner, Jennifer, Contributing Editor has reference to this Academic Journal, PHwiki organized this Journal Historically, Caltech physics has focused on the most fundamental problems, such as the structure of matter at the smallest conceivable scales, in addition to the structure of the universe at the largest conceivable scales. These problems are still enormously exciting, but there is also another frontier, just as exciting in addition to important, which might be called the entanglement frontier. Research in this area aims to underst in addition to in addition to exploit the exotic in addition to baffling correlations exhibited by quantum systems. State-of-the-art experiments can be done on a tabletop, in addition to there are very strong ties between experiment in addition to theory. In the 21st century, building strength in quantum many-body theory has been a high priority as long as Caltech physics, in addition to we have been quite successful. Furthermore, links to the theory of computation in addition to to atomic-molecular-optical physics make this research highly interdisciplinary, something Caltech does especially well. A central theme: seeking new paradigms as long as describing universal emergent phenomena in quantum systems containing many particles. We need new ideas to erect a gr in addition to unified theory of exotic quantum systems! Quantum Entanglement classically correlated socks quantumly correlated photons There is just one way to look at a classical bit (like the color of my sock), but there are complementary ways to observe a quantum bit (like the polarization of a single photon). Thus correlations among qubits are richer in addition to much more interesting than correlations among classical bits. A quantum system with two parts is entangled when its joint state is more definite in addition to less r in addition to om than the state of each part by itself. Looking at the parts one at a time, you can learn everything about a pair of socks, but not about a pair of qubits!

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The quantum correlations of many entangled qubits cannot be easily described in terms of ordinary classical in as long as mation. To give a complete classical description of one typical (highly entangled) state of just a few hundred qubits would require more bits than the number of atoms in the visible universe! It will never be possible, even in principle to write down such a description. We cant even hope to describe the state of a few hundred qubits in terms of classical bits. Thats why highly correlated quantum systems can behave in ways that we find hard to underst in addition to . But it also means that controlling highly entangled systems might be very powerful. As Feynman first suggested in 1981, a computer that operates on qubits rather than bits (a quantum computer) should be able to per as long as m tasks that are beyond the capability of any conceivable digital computer! Decoherence

Decoherence Decoherence explains why quantum phenomena, though observable in the microscopic systems studied in the physics lab, are not manifest in the macroscopic physical systems that we encounter in our ordinary experience. Decoherence ERROR! How can we protect a quantum system from decoherence in addition to other sources of error Why Fellowships In theory as in experiment, students in addition to postdocs make an essential contribution to the research ef as long as t. Thats particularly true when it comes to exploiting interdisciplinary opportunities in addition to fast-breaking developments. Students in addition to postdocs can provide the glue that binds different research groups together, in addition to often they lead the faculty into new territory rather than the other way around. Gottesman: Quantum error-correcting codes Smith: Quantum channel capacities Bonderson: Experimental signature of nonabelian statistics. Chang: Entangling mechanical oscillators Bacon: Self-correcting systems Verstraete: Complexity of quantum problems

Efficient classical simulation of quantum systems with bounded entanglement In general, there is no succinct classical description of the quantum state of a system of n qubits. But suppose, e.g., as long as qubits arranged in one dimension, that as long as any way of dividing the line into two segments, the strength of the quantum correlation (the amount of entanglement) between the two parts is bounded above by a constant, independent of n. Vidal showed that in that case a succinct description is possible, with O(n) parameters rather than 2n, in addition to that the description can be easily updated as the state evolves (if the interactions are local). This makes precise the idea that entanglement is the source of a quantum computers power: if the quantum computer does not become highly entangled, it can be efficiently simulated by a classical computer. Furthermore, in one-dimensional systems with local interactions, the entanglement increases no more rapidly than log n, in addition to an efficient classical simulation of real time evolution is possible. Universal properties of entanglement For the ground state of a large two-dimensional quantum system, consider the entanglement of a disk (circumference L) with the rest of the system. For a system with a nonzero energy gap, the entanglement is: The universal additive term, the topological entanglement entropy, is a global feature of the many-body quantum entanglement, characterizing the topological order of the gapped two-dimensional system. There is a simple as long as mula as long as the universal constant , in terms of the properties of the particle excitations of the system. Term proportional to L, arising from short distance fluctuations near the boundary, is nonuniversal. Additive correction is universal (independent of geometry in addition to microscopic details). Quantum In as long as mation Science Atomic-Molecular Optical Physics Condensed Matter Physics CEQS!

## Hillner, Jennifer Contributing Editor

Hillner, Jennifer is from United States and they belong to Wired Magazine and they are from San Francisco, United States got related to this Particular Journal. and Hillner, Jennifer deal with the subjects like Computers; Information Technology Industry

## Journal Ratings by Bidwell Training Center Inc

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