ATOMIC PHYSICS 20: XX International Conference on Atomic Physics - ICAP 2006
869(2006); http://dx.doi.org/10.1063/1.2400627View Description Hide Description
First‐time participants in ICAP might feel overwhelmed by the flood of research reported at this conference. It is important to realize, however, that contemporary interest in areas of high activity such as quantum fluids, precision measurements, optical metrology and quantum information did not emerge spontaneously, but evolved over time. To illustrate this I shall show how the seeds of some of the research reported at this conference can be discerned in talks given in the ICAPs of former years.
869(2006); http://dx.doi.org/10.1063/1.2400628View Description Hide Description
A delightful feature of atomic physics is the frequency with which unexpected discoveries and ideas send research off in exciting new directions. These changes make the field interesting, but make predictions of the future unreliable. Nevertheless, speculations on the future of the field can be valuable.
869(2006); http://dx.doi.org/10.1063/1.2400629View Description Hide Description
Modern society needs a better approach to science education. Research is showing that the typical student is not gaining the desired understanding of science from their classes. Research can also explain this result by showing that the teaching practices in many science courses go counter to what is known for how to achieve effective learning. This article discusses these results as well as pointing out how research provides guidance for how to improve the teaching of science.
869(2006); http://dx.doi.org/10.1063/1.2400630View Description Hide Description
Theories unifying gravity with other interactions suggest temporal and spatial variation of the fundamental “constants” in expanding Universe. The spatial variation can explain a fine tuning of the fundamental constants which allows humans (and any life) to appear. We appeared in the area of the Universe where the values of the fundamental constants are consistent with our existence.
We present a review of recent works devoted to the variation of the fine structure constant α, strong interaction and fundamental masses. There are some hints for the variation in quasar absorption spectra. Big Bang nucleosynthesis, and Oklo natural nuclear reactor data.
A very promising method to search for the variation of the fundamental constants consists in comparison of different atomic clocks. Huge enhancement of the variation effects happens in transition between accidentally degenerate atomic and molecular energy levels. A new idea is to build a “nuclear” clock based on the ultraviolet transition between very low excited state and ground state in Thorium nucleus. This may allow to improve sensitivity to the variation up to 10 orders of magnitude!
Huge enhancement of the variation effects is also possible in cold atomic and molecular collisions near Feshbach resonance.
869(2006); http://dx.doi.org/10.1063/1.2400631View Description Hide Description
A novel and highly accurate (at the level of Δλ/λ = 5 × 10−8) database of 233 spectral lines in the Lyman and Werner bands of H2 is determined via laboratory spectroscopy employing a narrowband and tunable extreme ultraviolet laser system. Furthermore an updated set of so‐called Ki coefficients, representing the sensitivity of each spectral line on a variation of the proton‐to‐electron mass ratio μ = mp/me are derived for all lines in the H2 spectrum. The laboratory wavelengths and Ki ’s are used in a comparison with a recent set of highly accurate H2 spectral lines observed in the Q 0347–383 and Q 0405–443 quasars yielding a fractional change in the mass‐ratio of Δμ/μ = 2.4 ± 0.6 × 10−5 (1σ). This result indicates, at a 4σ confidence level, that μ may have decreased in the past 12 billion years.
869(2006); http://dx.doi.org/10.1063/1.2400632View Description Hide Description
We present progress towards a new measurement of the electron electric dipole moment using a cold supersonic beam of YbF molecules. Data are currently being taken with a sensitivity of . We therefore expect to make an improvement over the Tl experiment of Commins’ group, which currently gives the most precise result. We discuss the systematic and statistical errors and comment on the future prospect of making a measurement at the level of .
869(2006); http://dx.doi.org/10.1063/1.2400633View Description Hide Description
The present status of quantum electrodynamics (QED) theory of heavy few‐electrons is reviewed. The theoretical results are compared with available experimental data. A special attention is focused on tests of QED at strong fields and on determination of the fundamental constants. A recent progress on calculations of the QED corrections to the parity nonconserving 6s‐7s transition amplitude in neutral Cs is also discussed.
869(2006); http://dx.doi.org/10.1063/1.2400634View Description Hide Description
Accumulation, storing and cooling techniques play an increasingly important role in many areas of science. These procedures can be applied in Penning traps and storage rings to ions. In this way, quantum electrodynamics can be tested in extreme electromagnetic fields by measuring hyperfine structure splittings. Lamb shifts, or g‐factors in hydrogen‐like heavy systems such as U91+ or Pb 81+. In addition, fundamental constants or nuclear properties like the atomic mass can be determined. In the case of a radioactive ion, the fate of an individual ion, undergoing a nuclear decay, can be studied in detail by observing the disappearance of the signal of the mother and the appearance of that of the daughter isotope. Presently, the Highly‐charged Ion TRAP (HITRAP) facility is being built up at GSI. Stable or radioactive highly charged ions are produced by colliding relativistic ions with a target. After electron cooling and deceleration in the storage ring ESR at GSI, these ions are ejected, decelerated further, and injected into a Penning trap where cooling to 4 K takes place. From there, the cooled highly charged ions such as hydrogen‐like uranium are transferred at low energy to different experimental set‐ups which are being built up by the international HITRAP Collaboration.
869(2006); http://dx.doi.org/10.1063/1.2400635View Description Hide Description
A new measurement resolves the cyclotron and spin levels for a single‐electron quantum cyclotron to obtain a dimensionless electron magnetic moment, g, to 7.6 parts in 1013 (nearly six times better than in the past) and shifted by 1.7 standard deviations. The new g, with a quantum electrodynamics (QED) calculation, determines the fine structure constant with a 0.7 ppb uncertainty — ten times smaller than for atom‐recoil determinations. Remarkably, this 100 mK measurement probes for internal electron structure at 130 GeV.
869(2006); http://dx.doi.org/10.1063/1.2400636View Description Hide Description
“Very high precision physics has always appealed to me. The steady improvement in technologies that afford higher and higher precision has been a regular source of excitement and challenge during my career. In science, as in most things, whenever one looks at something more closely, new aspects almost always come into play …” With these word from the book “How the Laser happened”, Charles H. Townes expresses a passion for precision that is now shared by many scientists. Masers and lasers have become indispensible tools for precision measurements. During the past few years, the advent of femtosecond laser frequency comb synthesizers has revolutionized the art of directly comparing optical and microwave frequencies. Inspired by the needs of precision laser spectroscopy of the simple hydrogen atom, such frequency combs are now enabling ultra‐precise spectroscopy over wide spectral ranges. Recent laboratory experiments are already setting stringent limits for possible slow variations of fundamental constants. Laser frequency combs also provide the long missing clockwork for optical atomic clocks that may ultimately reach a precision of parts in 1018 and beyond. Such tools will open intriguing new opportunities for fundamental experiments including new tests of special and general relativity. In the future, frequency comb techniques may be extended into the extreme ultraviolet and soft xray regime, opening a vast new spectral territory to precision measurements. Frequency combs have also become a key tool for the emerging new field of attosecond science, since they can control the electric field of ultrashort laser pulses on an unprecedented time scale. The biggest surprise in these endeavours would be if we found no surprise.
869(2006); http://dx.doi.org/10.1063/1.2400637View Description Hide Description
Ultracold atoms and molecules provide ideal stages for precision tests of fundamental physics. With microkelvin neutral strontium atoms confined in an optical lattice, we have achieved a fractional resolution of 4 × 10−15 on the 1 S 0 − 3 P 0 doubly‐forbidden 87Sr clock transition at 698 nm. The overall systematic uncertainty of the clock is evaluated below the 10−15 level. The ultrahigh spectral resolution permits resolving the nuclear spin states of the clock transition at small magnetic fields, leading to measurements of the 3 P 0 magnetic moment and metastable lifetime. In addition, photoassociation spectroscopy performed on the narrow 1 S 0 − 3 P 1 transition of 88Sr shows promise for efficient optical tuning of the ground state scattering length and production of ultracold ground‐state molecules. Lattice‐confined Sr2 molecules are suitable for constraining the time‐variation of electron‐proton mass ratio. In a separate experiment, cold, ground state polar molecules produced from Stark decelerators have enabled an order of magnitude improvement in measurement precision of ground‐state, Λ‐doublet microwave transitions in the OH molecule. Comparing the laboratory results to those from OH megamasers in interstellar space will allow a sensitivity of 10−6 for measuring the potential time variation of the fundamental fine structure constant Δα/α over 1010 years. These results have also led to improved understandings in the molecular structure. The study of the low magnetic field behavior of OH in its 2Π3/2 ro‐vibronic ground state precisely determines a differential Landé g‐factor between opposite parity components of the Λ‐doublet.
869(2006); http://dx.doi.org/10.1063/1.2400638View Description Hide Description
Forbidden transitions in single laser‐cooled trapped ions provide highly stable and accurate references for optical frequency standards. This paper describes recent progress on strontium and ytterbium ion optical frequency standards under development at NPL.
869(2006); http://dx.doi.org/10.1063/1.2400639View Description Hide Description
The basic requirements for quantum computing and quantum simulation (single‐ and multi‐qubit gates, long memory times, etc.) have been demonstrated in separate experiments on trapped ions. Construction of a large‐scale information processor will require synthesis of these elements and implementation of high‐fidelity operations on a very large number of qubits. This is still well in the future. NIST and other groups are addressing part of the scaling issue by trying to fabricate multi‐zone arrays of traps that would allow highly‐parallel and scalable processing. In the near term, some simple quantum processing protocols are being used to aid in quantum metrology, such as in atomic clocks. As the number of qubits increases, Schrödinger’s cat paradox and the measurement problem in quantum mechanics become more apparent; with luck, trapped ion systems might be able to shed light on these fundamental issues.
869(2006); http://dx.doi.org/10.1063/1.2400640View Description Hide Description
Entangled states of atoms prepared in a decoherence‐free subspace are shown to be useful for precision spectroscopy. Energy level shifts can be measured by using a pair of atoms in a Bell state for performing phase‐estimation by generalized Ramsey experiments. The immunity of decoherence‐free subspaces against certain sources of noise allows for long excitation times in the presence of noise that would render single‐atom experiments impossible. We employ this technique for a measurement of the electric quadrupole moment Θ of the meta‐stable 3D 5/2 level of 40Ca+ which is found to be .
869(2006); http://dx.doi.org/10.1063/1.2400641View Description Hide Description
We review our recent work towards extending quantum control techniques developed in AMO physics to manipulate quantum systems in the solid‐state. These systems feature a number of unique opportunities and difficult challenges. Specifically we describe our efforts toward understanding and controlling the complex environment of solid‐state quantum bits, coupling them over macroscopic distances as well as ideas for scaling to multi‐qubit systems.
869(2006); http://dx.doi.org/10.1063/1.2400642View Description Hide Description
We describe the integration of polar molecules with mesoscopic solid state devices in a way that produces robust, coherent, quantum‐level control with applications for quantum information processing. The exceptional features of polar molecules, i.e. long‐lived rotational states in combination with electric dipole moments of several Debye, provide the necessary ingredients to achieve strong coupling to the quantized field of a high‐Q microwave cavity. We discuss two scenarios, where quantum information is stored either in rotational states of a single molecule or in collective spin excitation of an ensemble of molecules. In the latter case we benefit from an enhanced coupling strength, which allows a coherent transfer of quantum information between molecules and solid state qubits.
869(2006); http://dx.doi.org/10.1063/1.2400643View Description Hide Description
Mirrors are ideal tools for controlling the optical and motional properties of an atom. To understand the physics of the light force in a cavity, and to explain why this force can be so much larger than in free space, we present an intuitive corpuscular picture based on the notion of cavity‐enhanced photon scattering. We also discuss a nonintuitive phenomenon that finds no simple explanation in terms of photon scattering and that we attribute to the wave aspect of light, Both particle and wave picture provide a complementary description of the main features of atomic motion in a cavity, in particular in the strong‐coupling regime.
869(2006); http://dx.doi.org/10.1063/1.2400644View Description Hide Description
Current experiments in our group explore the quantum interface between matter and light, with the goal of achieving coherent control for implementing quantum information protocols and quantum networks. We outline recent progress in this direction, including localization to the ground state of motion for an atom trapped in an optical cavity, observation of strong coupling between single Cesium atoms and a monolithic resonator, and generation and characterization of entanglement stored in remote atomic ensembles.
869(2006); http://dx.doi.org/10.1063/1.2400645View Description Hide Description
We describe a recent experiment performed with rubidium atoms (87Rb), aiming at studying the coherence properties of a two‐dimensional gas of bosonic particles at low temperature. We have observed in particular a Berezinskii‐Kosterlitz‐Thouless (BKT) type crossover in the system, using a matter wave heterodyning technique. At low temperatures, the gas is quasi‐coherent on the length scale set by the system size. As the temperature is increased, the loss of long‐range coherence coincides with the onset of the proliferation of free vortices, in agreement with the microscopic BKT theory.