We demonstrate the controlled generation of Fock states with up to 15 photons in a microwave coplanar waveguide resonator coupled to a superconducting phase qubit. The subsequent decay of the Fock states, due to dissipation, is then monitored by varying the time delay between preparing the state and performing a number-state analysis. We find that the decay dynamics can be described by a master equation where the lifetime of the $n$-photon Fock state scales as $1/n$, in agreement with theory. We have also generated a coherent state in the microwave resonator, and monitored its decay process. We demonstrate that the coherent state maintains a Poisson distribution as it decays, with an average photon number that decreases with the same characteristic decay time as the one-photon Fock state.

The relaxation of a quantum field stored in a high-$Q$ superconducting cavity is monitored by nonresonant Rydberg atoms. The field, subjected to repetitive quantum nondemolition photon counting, undergoes jumps between photon number states. We select ensembles of field realizations evolving from a given Fock state and reconstruct the subsequent evolution of their photon number distributions. We realize in this way a tomography of the photon number relaxation process yielding all the jump rates between Fock states. The damping rates of the $n$ photon states ($0\le n\le 7$) are found to increase linearly with $n$. The results are in excellent agreement with theory including a small thermal contribution.

There are two different proposals for the momentum of light in a transparent dielectric of refractive index $n$: Minkowski’s version $nE/c$ and Abraham’s version $E/(nc)$, where $E$ and $c$ are the energy and vacuum speed of light, respectively. Despite many tests and debates over nearly a century, momentum of light in a transparent dielectric remains controversial. In this Letter, we report a direct observation of the inward push force on the free end face of a nanometer silica filament exerted by the outgoing light. Our results suggest that Abraham’s momentum is correct.

Unique electronic properties of self-organized Au atom chains on Ge(001) in novel $c(8\times 2)$ long-range order are revealed by scanning tunneling microscopy. Along the nanowires an exceptionally narrow conduction path exists which is virtually decoupled from the substrate. It is laterally confined to the ultimate limit of single atom dimension, and is strictly separated from its neighbors, as not previously reported. The resulting tunneling conductivity shows a dramatic inhomogeneity of 2 orders of magnitude. The atom chains thus represent an outstandingly close approach to a one-dimensional electron liquid.

The second law of thermodynamics requires that directed motion be accompanied by dissipation of energy. Here we demonstrate the working principles of a bipedal molecular motor. The motor is constructed from DNA and is driven by the hybridization of a DNA fuel. We show how the catalytic activities of the feet can be coordinated to create a Brownian ratchet that is in principle capable of directional and processive movement along a track. This system can be driven away from equilibrium, demonstrating the potential of the motor to do work.

The shape of a weightless spinning liquid droplet is governed by the balance between the surface tension and centrifugal forces. The axisymmetric shape for slow rotation becomes unstable to a nonaxisymmetric distortion above a critical angular velocity, beyond which the droplet progresses through a series of 2-lobed shapes. Theory predicts the existence of a family of 3- and 4-lobed equilibrium shapes at higher angular velocity. We investigate the formation of a triangular-shaped magnetically levitated water droplet, driven to rotate by the Lorentz force on an ionic current within the droplet. We also study equatorial traveling waves which give the droplet threefold, fourfold, and fivefold symmetry.

${\mathrm{Tb}}_2{\mathrm{Sn}}_2{\mathrm{O}}_7$ has been proposed as an ordered spin ice, but the precise nature of the low temperature magnetic state remains uncertain. Recent independent muon spin relaxation ($\mu \mathrm{SR}$) investigations suggest the possibility of exotic ground states with static order precluded on time scales longer than ${10}^{-6}\mathrm{s}$. Here the more conventional hypothesis of canted ferromagnetism is tested by means of $\mu \mathrm{SR}$ with the muons stopped outside the sample, as well as ultralow field bulk magnetization measurements. The field cooled state shows conventional static order, while the zero field cooled state may be interpreted in terms of conventional closed domains. These results rule out purely dynamical ground states and illustrate the value of exterior muon implantation as a complement to the conventional technique.

We have observed laserlike emission of surface plasmon polaritons (SPPs) decoupled to the glass prism in an attenuated total reflection setup. SPPs were excited by optically pumped molecules in a polymeric film deposited on the top of a silver film. Stimulated emission was characterized by a distinct threshold in the input-output dependence and narrowing of the emission spectrum. The observed stimulated emission and corresponding compensation of the metallic absorption loss by gain enables many applications of metamaterials and nanoplasmonic devices.

We report a method of creating electrostatically induced quantum dots by thermal diffusion of interstitial Mn ions out of a $p$-type (GaMn)As layer into the vicinity of a GaAs quantum well. This approach creates deep, approximately circular, and strongly confined dotlike potential minima in a large ($200\mu \mathrm{m}$) mesa diode structure without need for advanced lithography or electrostatic gating. Magnetotunneling spectroscopy of an individual dot reveals the symmetry of its electronic eigenfunctions and a rich energy level spectrum of Fock-Darwin-like states with an orbital angular momentum component $|l_z|$ from 0 to 11.

The 7 year data set of the Milagro TeV observatory contains $2.2\times {10}^{11}$ events of which most are due to hadronic cosmic rays. These data are searched for evidence of intermediate scale structure. Excess emission on angular scales of $\sim 10°$ has been found in two localized regions of unknown origin with greater than $12\sigma$ significance. Both regions are inconsistent with pure gamma-ray emission with high confidence. One of the regions has a different energy spectrum than the isotropic cosmic-ray flux at a level of $4.6\sigma$, and it is consistent with hard spectrum protons with an exponential cutoff, with the most significant excess at $\sim 10\mathrm{TeV}$. Potential causes of these excesses are explored, but no compelling explanations are found.

We present a LIGO search for short-duration gravitational waves (GWs) associated with soft gamma ray repeater (SGR) bursts. This is the first search sensitive to neutron star $f$ modes, usually considered the most efficient GW emitting modes. We find no evidence of GWs associated with any SGR burst in a sample consisting of the 27 Dec. 2004 giant flare from SGR $1806-20$ and 190 lesser events from SGR $1806-20$ and SGR $1900+14$. The unprecedented sensitivity of the detectors allows us to set the most stringent limits on transient GW amplitudes published to date. We find upper limit estimates on the model-dependent isotropic GW emission energies (at a nominal distance of 10 kpc) between $3\times {10}^{45}$ and $9\times {10}^{52}$ erg depending on waveform type, detector antenna factors and noise characteristics at the time of the burst. These upper limits are within the theoretically predicted range of some SGR models.

High-speed video is used to analyze the pinch-off of xenon in water. By varying the pressure in the xenon from 0.05 to 68 atm, the mass density ratio $D={\rho }_{\mathrm{int}}/{\rho }_{\mathrm{ext}}$ of the interior gaseous xenon ${\rho }_{\mathrm{int}}$ to the exterior liquid water ${\rho }_{\mathrm{ext}}$ can be varied by over 3 orders of magnitude. Both the shape of the pinch region and the power law that governs the collapse of the minimum neck radius are distinctly different for the low $D$ (bubblelike) and high $D$ (dropletlike) cases. We show that there is a rather abrupt transition between these types of behavior near $D\approx 0.25$.

The ground state hyperfine splitting of ${}^7\mathrm{Be}^{+}$ has been measured by laser-microwave double-resonance spectroscopy in the online rf trap of RIKEN’s slow RI-beam facility. Be ions produced by projectile fragmentation of ${}^{13}\mathrm{C}$ at $\approx 1\mathrm{GeV}$ were thermalized in a rf ion guide gas cell and subsequently laser cooled in the ion trap to $\approx 1\mu \mathrm{eV}$. This ${10}^{15}$-fold reduction of the kinetic energy allows precision spectroscopy of these ions. A magnetic hfs constant of $A=-742.77228(43)\mathrm{MHz}$ was measured for ${}^7\mathrm{Be}^{+}$, from which a nuclear magnetic moment of ${\mu }_I=-1.39928(2){\mu }_N$ was deduced.

The collapse of turbulence, observable in shear flows at low Reynolds numbers, raises the question if turbulence is generically of a transient nature or becomes sustained at some critical point. Recent data have led to conflicting views with the majority of studies supporting the model of turbulence turning into an attracting state. Here we present lifetime measurements of turbulence in pipe flow spanning 8 orders of magnitude in time, drastically extending all previous investigations. We show that no critical point exists in this regime and that in contrast to the prevailing view the turbulent state remains transient. To our knowledge this is the first observation of superexponential transients in turbulence, confirming a conjecture derived from low-dimensional systems.

We study self-diffusion in complex fluids within dynamic density functional theory and explicitly account for the coupling to the fluctuating background. Applying the formalism to nematic and smectic liquid crystals, we find the temporary cages formed by neighboring particles to compete with permanent barriers in nonuniform systems, resulting in non-Gaussian diffusive motion that in different directions becomes correlated. Qualitative agreement with recent experiments demonstrates the importance of explicitly dealing with time-dependent self-consistent molecular fields.

We report the spontaneous formation of a plasma from a gas of cold Rydberg molecules. Double-resonant laser excitation promotes nitric oxide, cooled to 1 K in a seeded supersonic molecular beam, to single Rydberg states extending as deep as $80{\mathrm{cm}}^{-1}$ below the lowest ionization threshold. The density of excited molecules in the illuminated volume approaches $1\times {10}^{13}{\mathrm{cm}}^{-3}$. This population evolves to produce free electrons and a durable cold plasma of electrons and intact ${\mathrm{NO}}^{+}$ ions.

We consider two dielectric membranes suspended inside a Fabry-Perot cavity, which are cooled to a steady state via a drive by suitable classical lasers. We show that the vibrations of the membranes can be entangled in this steady state. They thus form two mechanical, macroscopic degrees of freedom that share steady state entanglement.

We demonstrate in a superconducting qubit the conditional recovery (uncollapsing) of a quantum state after a partial-collapse measurement. A weak measurement extracts information and results in a nonunitary transformation of the qubit state. However, by adding a rotation and a second partial measurement with the same strength, we erase the extracted information, canceling the effect of both measurements. The fidelity of the state recovery is measured using quantum process tomography and found to be above 70% for partial-collapse strength less than 0.6.

A new type of cloak is discussed: one that gives all cloaked objects the appearance of a flat conducting sheet. It has the advantage that none of the parameters of the cloak is singular and can in fact be made isotropic. It makes broadband cloaking in the optical frequencies one step closer.

From neutron diffraction measurements on a quasi-1D Ising-like ${\mathrm{Co}}^{2+}$ spin compound ${\mathrm{BaCo}}_2{\mathrm{V}}_2{\mathrm{O}}_8$, we observed an appearance of a novel type of incommensurate ordering in magnetic fields. This ordering is essentially different from the Néel-type ordering, which is expected for the classical system, and the peculiar spin structure is caused by quantum fluctuation inherent in the quantum spin chain. A Tomonaga-Luttinger liquid nature characteristic of the gapless quantum 1D system is responsible for the realization of the incommensurate ordering.