Recent Noteworthy Physics Papers

[ZapperZ]

D J Kapner et al. " Tests of the Gravitational Inverse-Square Law below the Dark-Energy Length Scale", Phys. Rev. Lett. 98 021101 (2007)

Abstract: We conducted three torsion-balance experiments to test the gravitational inverse-square law at separations between 9.53 mm and 55 µm, probing distances less than the dark-energy length scale lambdad=radical(radix(4)[h-bar]c/rho[sub d])[approximate]85 µm. We find with 95% confidence that the inverse-square law holds (|alpha|<=1) down to a length scale lambda=56 µm and that an extra dimension must have a size R<=44 µm.

Thanks for your contribution, but this paper was highlighted already 2 years ago here:

https://www.physicsforums.com/showpost.php?p=1301594&postcount=39

As per the "theme" of this thread, we try to highlight papers within the past year. If you are unsure if a paper has been highlighted here already, do a search on the thread on the first author's name.

Zz.

 

[ZapperZ]

S. Rao et al. "Measurement of Mechanical Forces Acting on Optically Trapped Dielectric Spheres Induced by Surface-Enhanced Raman Scattering, Phys. Rev. Lett. v.102, p.087401 (2009).

Abstract: Surface enhanced Raman scattering (SERS) is studied from optically trapped dielectric spheres partially covered with silver colloids in a solution with SERS active molecules. The Raman scattering and Brownian motion of the sphere are simultaneously measured to reveal correlations between the enhancement of the Raman signal and average position of the sphere. The correlations are due to the momenta transfer of the emitted Raman photons from the probe molecules. The addition of a mechanical force measurement provides a different dimension to the study of Raman processes.

You may also read the Physical Review http://focus.aps.org/story/v24/st12" .

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[Cthugha]

A. J. Bennett et al., "Interference of dissimilar photon sources, Nature Physics v.5 p.715-717 (2009).

Abstract: If identical photons meet at a semi-transparent mirror they seem to leave in the same direction, an effect called 'two-photon interference'. It has been known for some time that this effect should occur for photons generated by dissimilar sources with no common history, provided the measurement cannot distinguish between the photons. Here, we report a technique for observing such interference with isolated, unsynchronized sources for which the coherence times differ by several orders of magnitude. In an experiment we cause photons generated by different physical processes, with different photon statistics, to interfere. One of the sources is stimulated emission from a tunable laser, which has Poissonian statistics and a nanoelectronvolt bandwidth. The other is spontaneous emission from a quantum dot in a p–i–n diode with a few-microelectronvolt linewidth. We develop a theory to explain the visibility of interference, which is primarily limited by the timing resolution of our detectors.

It is well known that there is a close connection between indistinguishability and interference. Therefore recently there have been lots of efforts to test to which extent distinguishable photons can be made indistinguishable in terms of an experiment. This has been shown in several systems before, including single atoms, ions, consecutive single photons from single quantum dots and even different semiconductor nanostructures. Bennett et al. now prove that even photons from completely different light sources can show two-photon interference.

 

[adsf]

is there any papers published at the high-school level?

 

[|squeezed>]

Quantum Zeno effect explains magnetic-sensitive radical-ion-pair reactions , Phys. Rev. E 80, 056115 (2009) - http://arxiv.org/abs/0806.0739

Abstract:Chemical reactions involving radical-ion pairs are ubiquitous in biology, since not only are they at the basis of the photosynthetic reaction chain, but are also assumed to underlie the biochemical magnetic compass used by avian species for navigation. Recent experiments with magnetic-sensitive radical-ion-pair reactions provided strong evidence for the radical-ion-pair magnetoreception mechanism, verifying the expected magnetic sensitivities and chemical product yield changes. It is here shown that the theoretical description of radical-ion-pair reactions used since the 70s cannot explain the observed data, because it is based on phenomenological equations masking quantum coherence effects. The fundamental density-matrix equation derived here from basic quantum measurement theory considerations naturally incorporates the quantum Zeno effect and readily explains recent experimental observations on low- and high magnetic-field radical-ion-pair reactions.

 

[ZapperZ]

R. Gerritsma et al. "Quantum simulation of the Dirac equation", Nature v.463, p.68 (2010) .

Abstract: The Dirac equation successfully merges quantum mechanics with special relativity. It provides a natural description of the electron spin, predicts the existence of antimatter and is able to reproduce accurately the spectrum of the hydrogen atom. The realm of the Dirac equation—relativistic quantum mechanics—is considered to be the natural transition to quantum field theory. However, the Dirac equation also predicts some peculiar effects, such as Klein’s paradox and ‘Zitterbewegung’, an unexpected quivering motion of a free relativistic quantum particle. These and other predicted phenomena are key fundamental examples for understanding relativistic quantum effects, but are difficult to observe in real particles. In recent years, there has been increased interest in simulations of relativistic quantum effects using different physical set-ups in which parameter tunability allows access to different physical regimes. Here we perform a proof-of-principle quantum simulation of the one-dimensional Dirac equation using a single trapped ion set to behave as a free relativistic quantum particle. We measure the particle position as a function of time and study Zitterbewegung for different initial superpositions of positive- and negative-energy spinor states, as well as the crossover from relativistic to non-relativistic dynamics. The high level of control of trapped-ion experimental parameters makes it possible to simulate textbook examples of relativistic quantum physics.

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[ZapperZ]

R.B. Lanyon et al., "Towards quantum chemistry on a quantum computer" Nature Chemistry v.2, p.106 (2009).

Abstract: Exact first-principles calculations of molecular properties are currently intractable because their computational cost grows exponentially with both the number of atoms and basis set size. A solution is to move to a radically different model of computing by building a quantum computer, which is a device that uses quantum systems themselves to store and process data. Here we report the application of the latest photonic quantum computer technology to calculate properties of the smallest molecular system: the hydrogen molecule in a minimal basis. We calculate the complete energy spectrum to 20 bits of precision and discuss how the technique can be expanded to solve large-scale chemical problems that lie beyond the reach of modern supercomputers. These results represent an early practical step toward a powerful tool with a broad range of quantum-chemical applications.

You can read a http://www.wired.com/wiredscience/2010/01/quantum-computer-hydrogen-simulation/" .

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[Cthugha]

D. W. Berry, et al., "Fair-sampling assumption is not necessary for testing local realism" Phys. Rev. A 81, 012109 (2010).

Abstract: Almost all Bell inequality experiments to date have used postselection and therefore relied on the fair sampling assumption for their interpretation. The standard form of the fair sampling assumption is that the loss is independent of the measurement settings, so the ensemble of detected systems provides a fair statistical sample of the total ensemble. This is often assumed to be needed to interpret Bell inequality experiments as ruling out hidden-variable theories. Here we show that it is not necessary; the loss can depend on measurement settings, provided the detection efficiency factorizes as a function of the measurement settings and any hidden variable. This condition implies that Tsirelson’s bound must be satisfied for entangled states. On the other hand, we show that it is possible for Tsirelson’s bound to be violated while the Clauser-Horne-Shimony-Holt (CHSH)-Bell inequality still holds for unentangled states, and present an experimentally feasible example.

Although I do not care much about interpretational issues and all that nonlocality vs. local realism stuff, a lot of people around here do. Therefore some people on these forums might be interested in this formal treatment on the meaning of fair sampling.

 

[ZapperZ]

Holger Müller, Achim Peters, & Steven Chu "A precision measurement of the gravitational redshift by the interference of matter waves", Nature v.463, p.926 (2010).

Abstract: One of the central predictions of metric theories of gravity, such as general relativity, is that a clock in a gravitational potential U will run more slowly by a factor of 1 + U/c^2, where c is the velocity of light, as compared to a similar clock outside the potential. This effect, known as gravitational redshift, is important to the operation of the global positioning system, timekeeping and future experiments with ultra-precise, space-based clocks (such as searches for variations in fundamental constants). The gravitational redshift has been measured using clocks on a tower, an aircraft and a rocket, currently reaching an accuracy of 7 × 10^-5. Here we show that laboratory experiments based on quantum interference of atoms enable a much more precise measurement, yielding an accuracy of 7 × 10^-9. Our result supports the view that gravity is a manifestation of space-time curvature, an underlying principle of general relativity that has come under scrutiny in connection with the search for a theory of quantum gravity. Improving the redshift measurement is particularly important because this test has been the least accurate among the experiments that are required to support curved space-time theories.

You may read a report on this work at the http://physicsworld.com/cws/article/news/41740" .

Also, note the name of one of the authors of this paper. There is a "Steven Chu", who is currently the Secretary of the US Dept. of Energy! :)

Zz.

 

[ZapperZ]

H. Shishido et al., "Tuning the Dimensionality of the Heavy Fermion Compound CeIn3" Science v.327, p.980 (2010).

Abstract: Condensed-matter systems that are both low-dimensional and strongly interacting often exhibit unusual electronic properties. Strongly correlated electrons with greatly enhanced effective mass are present in heavy fermion compounds, whose electronic structure is essentially three-dimensional. We realized experimentally a two-dimensional heavy fermion system, adjusting the dimensionality in a controllable fashion. Artificial superlattices of the antiferromagnetic heavy fermion compound CeIn3 and the conventional metal LaIn3 were grown epitaxially. By reducing the thickness of the CeIn3 layers, the magnetic order was suppressed and the effective electron mass was further enhanced. Heavy fermions confined to two dimensions display striking deviations from the standard Fermi liquid low-temperature electronic properties, and these are associated with the dimensional tuning of quantum criticality.

Also see the Perspective article by Piers Coleman in the same issue.

This is a very interesting work since now, the "parameter" that is controlling the quantum phase transition is the dimensionality: 3D to 2D.

Zz.

 

[ZapperZ]

R. Reyes et al., "Confirmation of general relativity on large scales from weak lensing and galaxy velocities", Nature v.464, p.256 (2010).

Abstract: Although general relativity underlies modern cosmology, its applicability on cosmological length scales has yet to be stringently tested. Such a test has recently been proposed, using a quantity, E G, that combines measures of large-scale gravitational lensing, galaxy clustering and structure growth rate. The combination is insensitive to ‘galaxy bias’ (the difference between the clustering of visible galaxies and invisible dark matter) and is thus robust to the uncertainty in this parameter. Modified theories of gravity generally predict values of E G different from the general relativistic prediction because, in these theories, the ‘gravitational slip’ (the difference between the two potentials that describe perturbations in the gravitational metric) is non-zero, which leads to changes in the growth of structure and the strength of the gravitational lensing effect. Here we report that E G = 0.39 ± 0.06 on length scales of tens of megaparsecs, in agreement with the general relativistic prediction of E G ≈ 0.4. The measured value excludes a model1 within the tensor–vector–scalar gravity theory which modifies both Newtonian and Einstein gravity. However, the relatively large uncertainty still permits models within f(R) theory, which is an extension of general relativity. A fivefold decrease in uncertainty is needed to rule out these models.

Edit: See PhysicsWorld coverage of this:

http://physicsworld.com/cws/article/news/41948

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[ZapperZ]

Y. Kajiwara et al., "Transmission of electrical signals by spin-wave interconversion in a magnetic insulator" Nature v.464, p.262 (2010).

Abstract: The energy bandgap of an insulator is large enough to prevent electron excitation and electrical conduction. But in addition to charge, an electron also has spin, and the collective motion of spin can propagate—and so transfer a signal—in some insulators. This motion is called a spin wave and is usually excited using magnetic fields. Here we show that a spin wave in an insulator can be generated and detected using spin-Hall effects, which enable the direct conversion of an electric signal into a spin wave, and its subsequent transmission through (and recovery from) an insulator over macroscopic distances. First, we show evidence for the transfer of spin angular momentum between an insulator magnet Y3Fe5O12 and a platinum film. This transfer allows direct conversion of an electric current in the platinum film to a spin wave in the Y3Fe5O12 via spin-Hall effects. Second, making use of the transfer in a Pt/Y3Fe5O12/Pt system, we demonstrate that an electric current in one metal film induces voltage in the other, far distant, metal film. Specifically, the applied electric current is converted into spin angular momentum owing to the spin-Hall effect in the first platinum film; the angular momentum is then carried by a spin wave in the insulating Y3Fe5O12 layer; at the distant platinum film, the spin angular momentum of the spin wave is converted back to an electric voltage. This effect can be switched on and off using a magnetic field. Weak spin damping3 in Y3Fe5O12 is responsible for its transparency for the transmission of spin angular momentum. This hybrid electrical transmission method potentially offers a means of innovative signal delivery in electrical circuits and devices.

This appears to be the first instance of electrical signal being transmitted via spin waves. This should bring the possiblity of spintronics a step closer to reality.

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[ZapperZ]

P.J. Mohr and D.B. Newell, "The physics of fundamental constants", Am. J. Phys. v.78, p.338 (2010).

Abstract: This Resource Letter provides a guide to the literature on the physics of fundamental constants and their values as determined within the International System of Units (SI). Journal articles, books, and websites that provide relevant information are surveyed. Literature on redefining the SI in terms of exact values of fundamental constants is also included.

A very useful paper to have and to keep. Not only does it describe all of the major fundamental constants of our universe that we know of so far, but it also describes how they are measured/determined, AND gives you a boatload of references along with each of these constants.

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[ZapperZ]

M. Rypdal and K. Rypdal, "Testing Hypotheses about Sun-Climate Complexity Linking", Phys. Rev. Lett. v.104, p.128501 (2010).

Abstract: We reexamine observational evidence presented in support of the hypothesis of a sun-climate complexity linking by N. Scafetta and B. J. West, Phys. Rev. Lett. 90, 248701 (2003), which contended that the integrated solar flare index (SFI) and the global temperature anomaly (GTA) both follow Lévy walk statistics with the same waiting-time exponent μ≈2.1. However, their analysis does not account for trends in the signal, cannot deal correctly with infinite variance processes (Lévy flights), and suffers from considering only the second moment. Our analysis shows that properly detrended, the integrated SFI is well described as a Lévy flight, and the integrated GTA as a persistent fractional Brownian motion. These very different stochastic properties of the solar and climate records do not support the hypothesis of a sun-climate complexity linking.

The preprint of the manuscript http://complexityandplasmas.net/Preprints_files/sun-climate%20complexity%20link.pdf" .

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[ZapperZ]

S. Pironio et al., "Random numbers certified by Bell’s theorem", Nature v.464, p.1021 (2010).

Abstract: Randomness is a fundamental feature of nature and a valuable resource for applications ranging from cryptography and gambling to numerical simulation of physical and biological systems. Random numbers, however, are difficult to characterize mathematically, and their generation must rely on an unpredictable physical process. Inaccuracies in the theoretical modelling of such processes or failures of the devices, possibly due to adversarial attacks, limit the reliability of random number generators in ways that are difficult to control and detect. Here, inspired by earlier work on non-locality-based and device-independent quantum information processing, we show that the non-local correlations of entangled quantum particles can be used to certify the presence of genuine randomness. It is thereby possible to design a cryptographically secure random number generator that does not require any assumption about the internal working of the device. Such a strong form of randomness generation is impossible classically and possible in quantum systems only if certified by a Bell inequality violation15. We carry out a proof-of-concept demonstration of this proposal in a system of two entangled atoms separated by approximately one metre. The observed Bell inequality violation, featuring near perfect detection efficiency, guarantees that 42 new random numbers are generated with 99 per cent confidence. Our results lay the groundwork for future device-independent quantum information experiments and for addressing fundamental issues raised by the intrinsic randomness of quantum theory.

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[ZapperZ]

T. Hanaguri et al., "Unconventional s-Wave Superconductivity in Fe(Se,Te)", Science v.328, p.474 (2010).

Abstract: The superconducting state is characterized by a pairing of electrons with a superconducting gap on the Fermi surface. In iron-based superconductors, an unconventional pairing state has been argued for theoretically. We used scanning tunneling microscopy on Fe(Se,Te) single crystals to image the quasi-particle scattering interference patterns in the superconducting state. By applying a magnetic field to break the time-reversal symmetry, the relative sign of the superconducting gap can be determined from the magnetic-field dependence of quasi-particle scattering amplitudes. Our results indicate that the sign is reversed between the hole and the electron Fermi-surface pockets (s±-wave), favoring the unconventional pairing mechanism associated with spin fluctuations.

It is an amazing experiment. Not only have they clearly measured the pairing symmetry for the Cooper pairs in this family of superconductors, but they managed to detect the unusual and difficult-to-measure s±-wave symmetry! To my knowledge, this is the first time someone has experimentally determined this symmetry, using STM no less!

There is also a review article on this work written by J.E. Hoffman in the same issue of Science.

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[ZapperZ]

I. Afek et al., "High-NOON States by Mixing Quantum and Classical Light", Science v.328, p.879 (2010).

Abstract: Precision measurements can be brought to their ultimate limit by harnessing the principles of quantum mechanics. In optics, multiphoton entangled states, known as NOON states, can be used to obtain high-precision phase measurements, becoming more and more advantageous as the number of photons grows. We generated "high-NOON" states (N = 5) by multiphoton interference of quantum down-converted light with a classical coherent state in an approach that is inherently scalable. Super-resolving phase measurements with up to five entangled photons were produced with a visibility higher than that obtainable using classical light only.

Read a perspective article on this work in the same issue of Science. A summary of this work can also be found on the http://physicsworld.com/cws/article/news/42612" .

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[Cthugha]

C. L. Salter et al., "An entangled-light-emitting diode", Nature v.465, p.594 (2010).

Abstract: A quantum computer based on optical processes requires a source of entangled photons that can be delivered efficiently on demand. Such a source has now been developed: it involves a compact light-emitting diode with an embedded quantum dot that can be driven electrically to generate entangled photon pairs.

I already heard Mark Stevenson give a talk on this topic at QD 2010 and it was pretty obvious that it would just be a matter of time until we see the results in one of the big two journals. The realization of a semiconductor based, electrically pumped entangled photon source is one huge step to take entangled photons out of the lab and into the "real world", including commercial usage.

 

[ZapperZ]

J.T. Stewart et al., "Verification of Universal Relations in a Strongly Interacting Fermi Gas", Phys. Rev. Lett. 104, 235301 (2010).

Abstract: Many-body fermion systems are important in many branches of physics, including condensed matter, nuclear, and now cold atom physics. In many cases, the interactions between fermions can be approximated by a contact interaction. A recent theoretical advance in the study of these systems is the derivation of a number of exact universal relations that are predicted to be valid for all interaction strengths, temperatures, and spin compositions. These equations, referred to as the Tan relations, relate a microscopic quantity, namely, the amplitude of the high-momentum tail of the fermion momentum distribution, to the thermodynamics of the many-body system. In this work, we provide experimental verification of the Tan relations in a strongly interacting gas of fermionic atoms by measuring both the microscopic and macroscopic quantities in the same system.

You may read the http://physics.aps.org/articles/v3/48" , and also get a free download of the actual publication.

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[ZapperZ]

J.-P. Bocquet et al. "Limits on Light-Speed Anisotropies from Compton Scattering of High-Energy Electrons", Phys. Rev. Lett. v.104, p.241601 (2010).

Abstract: The possibility of anisotropies in the speed of light relative to the limiting speed of electrons is considered. The absence of sidereal variations in the energy of Compton-edge photons at the European Synchrotron Radiation Facility’s GRAAL facility constrains such anisotropies representing the first nonthreshold collision-kinematics study of Lorentz violation. When interpreted within the minimal standard-model extension, this result yields the two-sided limit of 1.6×10^-14 at 95% confidence level on a combination of the parity-violating photon and electron coefficients (κ˜o+)YZ, (κ˜o+)ZX, cTX, and cTY. This new constraint provides an improvement over previous bounds by 1 order of magnitude.

The http://arxiv.org/PS_cache/arxiv/pdf/1005/1005.5230v2.pdf" .

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[Count Iblis]

T. Goldman, Neutrino Oscillations and Energy-Momentum Conservation, Mod. Phys. Lett. A25, 479 (2010).

Abstract:

A description of neutrino oscillation phenomena is presented which is based on relativistic quantum mechanics and includes both entangled state and source dependent aspects, unlike both of the conventional approaches which use either equal energies or equal momenta for the different neutrino mass eigenstates. To second order in the neutrino masses, the standard result is recovered thus showing an absence of source dependence to this order. The time dependence of the wavefunction is found to be crucial to recovering the conventional result. An ambiguity appears at fourth order in the neutrino masses which generally leads to source dependence, but the standard formula can be promoted to this order by a plausible convention.

http://arxiv.org/abs/hep-ph/9604357"

 

[ZapperZ]

T. van Zoest et al., "Bose-Einstein Condensation in Microgravity", Science v.328, p.1540 (2010).

Abstract: Albert Einstein’s insight that it is impossible to distinguish a local experiment in a "freely falling elevator" from one in free space led to the development of the theory of general relativity. The wave nature of matter manifests itself in a striking way in Bose-Einstein condensates, where millions of atoms lose their identity and can be described by a single macroscopic wave function. We combine these two topics and report the preparation and observation of a Bose-Einstein condensate during free fall in a 146-meter-tall evacuated drop tower. During the expansion over 1 second, the atoms form a giant coherent matter wave that is delocalized on a millimeter scale, which represents a promising source for matter-wave interferometry to test the universality of free fall with quantum matter.

Also see the Perspective article on this paper in the same issue of Science.

A presentation viewgraphs by one of the authors http://www.sif.it/SIF/resources/public/files/va2009/seidel_0630.pdf" .

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[ZapperZ]

U. Sinha et al., "Ruling Out Multi-Order Interference in Quantum Mechanics, Science v.329, p.418 (2010).

Abstract:Quantum mechanics and gravitation are two pillars of modern physics. Despite their success in describing the physical world around us, they seem to be incompatible theories. There are suggestions that one of these theories must be generalized to achieve unification. For example, Born’s rule—one of the axioms of quantum mechanics—could be violated. Born’s rule predicts that quantum interference, as shown by a double-slit diffraction experiment, occurs from pairs of paths. A generalized version of quantum mechanics might allow multipath (i.e., higher-order) interference, thus leading to a deviation from the theory. We performed a three-slit experiment with photons and bounded the magnitude of three-path interference to less than 10^–2 of the expected two-path interference, thus ruling out third- and higher-order interference and providing a bound on the accuracy of Born’s rule. Our experiment is consistent with the postulate both in semiclassical and quantum regimes.

Review of this work can be found at http://www.physorg.com/news199009831.html" .

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[ultrafast]

I imagine APS' http://physics.aps.org/" showcases many of these papers.

 

[ZapperZ]

I imagine APS' http://physics.aps.org/" showcases many of these papers.

That site highlights only papers published in the APS journals (Physical Review family), since they provide free access to those papers.

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[ZapperZ]

E. Haller et al., "Pinning quantum phase transition for a Luttinger liquid of strongly interacting bosons", Nature v.466, p.597 (2010).

Abstract: Quantum many-body systems can have phase transitions even at zero temperature; fluctuations arising from Heisenberg’s uncertainty principle, as opposed to thermal effects, drive the system from one phase to another. Typically, during the transition the relative strength of two competing terms in the system’s Hamiltonian changes across a finite critical value. A well-known example is the Mott–Hubbard quantum phase transition from a superfluid to an insulating phase, which has been observed for weakly interacting bosonic atomic gases. However, for strongly interacting quantum systems confined to lower-dimensional geometry, a novel type of quantum phase transition may be induced and driven by an arbitrarily weak perturbation to the Hamiltonian. Here we observe such an effect—the sine–Gordon quantum phase transition from a superfluid Luttinger liquid to a Mott insulator, —in a one-dimensional quantum gas of bosonic caesium atoms with tunable interactions. For sufficiently strong interactions, the transition is induced by adding an arbitrarily weak optical lattice commensurate with the atomic granularity, which leads to immediate pinning of the atoms. We map out the phase diagram and find that our measurements in the strongly interacting regime agree well with a quantum field description based on the exactly solvable sine–Gordon model. We trace the phase boundary all the way to the weakly interacting regime, where we find good agreement with the predictions of the one-dimensional Bose–Hubbard model. Our results open up the experimental study of quantum phase transitions, criticality and transport phenomena beyond Hubbard-type models in the context of ultracold gases.

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[ZapperZ]

J. Leach et al., "Quantum Correlations in Optical Angle–Orbital Angular Momentum Variables", Science v.329, p.662 (2010).

Abstract: Entanglement of the properties of two separated particles constitutes a fundamental signature of quantum mechanics and is a key resource for quantum information science. We demonstrate strong Einstein, Podolsky, and Rosen correlations between the angular position and orbital angular momentum of two photons created by the nonlinear optical process of spontaneous parametric down-conversion. The discrete nature of orbital angular momentum and the continuous but periodic nature of angular position give rise to a special sort of entanglement between these two variables. The resulting correlations are found to be an order of magnitude stronger than those allowed by the uncertainty principle for independent (nonentangled) particles. Our results suggest that angular position and orbital angular momentum may find important applications in quantum information science.

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[ZapperZ]

O. Ben-David et al., "The Dynamics of the Onset of Frictional Slip", Science v.330, p.211 (2010).

Abstract: The way in which a frictional interface fails is critical to our fundamental understanding of failure processes in fields ranging from engineering to the study of earthquakes. Frictional motion is initiated by rupture fronts that propagate within the thin interface that separates two sheared bodies. By measuring the shear and normal stresses along the interface, together with the subsequent rapid real-contact-area dynamics, we find that the ratio of shear stress to normal stress can locally far exceed the static-friction coefficient without precipitating slip. Moreover, different modes of rupture selected by the system correspond to distinct regimes of the local stress ratio. These results indicate the key role of nonuniformity to frictional stability and dynamics with implications for the prediction, selection, and arrest of different modes of earthquakes.

We get frequent questions on the origin of friction and when things start to slip. This shows that even on something that we know at the "macroscopic" level, there's still a lot to learn at the microscopic scale.

Edit: The Science webpage has a tag that says "FREE Full Text" for this paper. I don't know if you get to see this paper for free, but http://www.sciencemag.org/cgi/content/abstract/330/6001/211?ijkey=7469109e591af519fde2f5aef4db1ed7c25df273&keytype2=tf_ipsecsha".

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[ZapperZ]

I. Altfeder et al., "Vacuum Phonon Tunneling", Phys. Rev. Lett. v.105, p.166101 (2010).

Abstract: Field-induced phonon tunneling, a previously unknown mechanism of interfacial thermal transport, has been revealed by ultrahigh vacuum inelastic scanning tunneling microscopy (STM). Using thermally broadened Fermi-Dirac distribution in the STM tip as in situ atomic-scale thermometer we found that thermal vibrations of the last tip atom are effectively transmitted to sample surface despite few angstroms wide vacuum gap. We show that phonon tunneling is driven by interfacial electric field and thermally vibrating image charges, and its rate is enhanced by surface electron-phonon interaction.

A Physical Review Focus article of this work http://focus.aps.org/story/v26/st15" .

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[ZapperZ]

L.A. Wray et al., "Observation of topological order in a superconducting doped topological insulator", Nature Physics v.6, p.855 (2010).

Abstract: [1]Experimental observation of topological order in three-dimensional bulk solids has recently led to a flurry of research activity. Unlike the two-dimensional electron gas or quantum Hall systems, three-dimensional topological insulators can harbour superconductivity and magnetism, making it possible to study the interplay between topologically ordered phases and broken-symmetry states. One outcome of this interplay is the possible realization of Majorana fermions—quasiparticles that are their own antiparticles—on topological surfaces, which is of great interest in fundamental physics. Here we present measurements of the bulk and surface electron dynamics in Bi2Se3 doped with copper with a transition temperature Tc up to 3.8 K, observing its topological character for the first time. Our data show that superconductivity occurs in a bulk relativistic quasiparticle regime where an unusual doping mechanism causes the spin-polarized topological surface states to remain well preserved at the Fermi level of the superconductor where Cooper pairing takes place. These results suggest that the electron dynamics in superconducting Bi2Se3 are suitable for trapping non-Abelian Majorana fermions. Details of our observations constitute important clues for developing a general theory of topological superconductivity in doped topological insulators.[/i]

A review of this paper http://news.softpedia.com/news/Split-Personality-Material-Found-at-Princeton-164508.shtml".

It won't be surprising if the Majorana fermions are first found in such a condensed matter system.

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