Atomic Physics Seminar

I will give an overview of searches for new physics with atomic systems, including the study of parity violation, search for EDM, and the search for variation of fundamental constants. The study of parity nonconservation in cesium led to a first measurement of the nuclear anapole moment and allowed to place constraints on weak meson-nucleon couplings. I will review the present status of atomic parity violation studies and the implications for searches for physics beyond the standard model and study of weak hadronic interactions. In the second part of my talk, I will discuss the state-of-the art atomic clock development focusing on the issue of the blackbody radiation shifts as well as application of clocks to the searches for variation of the fine-structure constant.

Host: 
Saffman
Speaker: Marianna Safronova University of Delaware

 

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Room and Building: 
5310 Chamberlin Hall

The divalent electronic structure of alkaline-earth metal atoms such as strontium gives rise to metastable, excited triplet levels and narrow intercombination transitions. These have been exploited for optical clocks, powerful laser cooling techniques that are critical for achieving quantum degeneracy in strontium, and proposals for quantum information architectures and studies of novel magnetism. Metastable excited electronic states also give rise to narrow photoassociation (PA) transitions that differ in many ways from traditional PA with broad, electric-dipole-allowed transitions. In this talk, we will describe narrow-line PA near the ^1S_0-^3P_1 intercombination transition in an ^88Sr Bose-Einstein condensate. This results in coherent PA and Rabi oscillations between atomic and molecular condensates. Transient shifts and broadenings of the excitation spectrum are clearly seen at short times, and they create an asymmetric excitation profile that only displays Rabi oscillations for blue detuning from resonance. Coherent PA is analogous to molecule formation with a magnetic Feshbach resonance.

Host: 
Saffman
Speaker: Tom Killian Rice University

 

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Room and Building: 
5310 Chamberlin Hall

Atom interferometry offers a number advantages to the field of precision metrology overt over optical interferometers due to the sensitivity of atoms to external electromagnetic fields and inertial forces. Utilising a circular waveguide has the further benefit of providing a strong common-mode rejection between paths and rotational sensitivity via the Sagnac effect, whilst also permitting longer interaction times compared to optical sensors. We present the first demonstration of a novel inductively coupled ring trap for cold atoms to create a circular waveguide of radius 5 mm. A uniform, ac magnetic field induces current in a copper ring, which creates an opposing magnetic field that is time-averaged to produce a smooth cylindrically symmetric ring trap. This resolves the issue of perturbations due to electrical connections and benefits from averaging out corrugation of the potential due to current meandering. A laser-cooled atomic sample is used to characterise the loading efficiency and adiabaticity of the magnetic potential, achieving a vacuum-limited lifetime in the trap. This technique is suitable for creating scalable toroidal waveguides for applications in matterwave interferometry, with a large enclosed area and long interaction times. Development of a second generation apparatus to utilise the ac ring trap for Sagnac interferometry with Bose (87Rb) and Fermi (40K) quantum degenerate gases is described.

Host: 
Saffman
Speaker: Jonathan Pritchard University of Strathclyde, Glasgow

 

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Room and Building: 
5310 Chamberlin

Understanding the origin of the elements is one of the major challenges of modern astrophysics. The oxygen in water molecules; the calcium in our bones; the uranium in our weapons---it's all stardust. But what about the details? The answers lie mostly with the stars. I will share recent observations from the high-resolution spectrograph on board the Hubble Space Telescope that teach us about how some of the heaviest elements have been produced. I will highlight connections between atomic physics, nuclear physics, and astronomy that have enabled these advances.

Host: 
Lawler & Zweibel
Speaker: Ian Roederer Carnegie Observatories

 

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Room and Building: 
5310 Chamberlin

Ultraold Rydberg gases are a promising system for exploring many ideas in the area of quantum computation, quantum optics, novel states of matter, and many-body physics. A key to understanding ultracold Rydberg gases and making progress in these exciting directions is to understand how Rydberg atoms interact with other atoms. We will review our understanding of Rydberg interactions including the effect of external fields. We will focus on describing interactions that lead to 2 types of novel molecule formation, so called 'trilobite' molecules and macrodimers. We have recently observed 'trilobite' molecules in an ultracold Cs gas and found that these molecules possess dipole moments in excess of 30D. In prior work, we detected electric field tunable Cs macrodimer molecules, molecules with bond lengths of ~5 microns. In this talk, we will compare and contrast these exotic forms of matter as well as try to place their study in the context of understanding Rydberg atom interactions quantitatively.

Host: 
Saffman
Speaker: James Shaffer University of Oklahoma

 

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Room and Building: 
5280 Chamberlin
Online community-based efforts such as Wikipedia have revolutionized the availability of information during the past decade and fundamentally reshaped our society. The coming decade may bring a similar revolution to scientific research by enabling users of the internet to participate in actual scientific endeavors. This democratized research has been pioneered by efforts such as SETI@Home and the science game Fold.It.

We expand this approach by developing an online-computer game, in which players assist in solving one of the high-profile technical challenges of the 21st century: the creation of a quantum computer, which will be able to outcompete all conventional computers combined at certain tasks. Specifically, the players will get a chance to participate in the search for robust gates in an architecture based on an optical tweezer manipulating individual atoms in an optical lattice. I will furthermore describe our effort to adapt the game approach to science education in high schools and higher education.

Finally, I will briefly describe recent experimental progress towards quantum control of the many-body state of ultra-cold atoms using non-destructive measurements and feedback.
Host: 
Saffman
Speaker: Prof. Jacob Sherson University of Aarhus, Denmark

 

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Room and Building: 
5310 Chamberlin
Ultracold gases doped with single impurity atoms are promising hybrid systems that pave the way for the realization of intriguing scenarios, such as studying polaron physics, forming local, coherent probes for a many-body system and coherent cooling of individual neutral atoms containing quantum information.

I will present our experiments of immersing single and few Cs atoms into an ultracold, thermal Rb cloud. We observe the sympathetic cooling of the impurity atoms, where the temperature is limited only by the temperature of the Rb gas. The thermalization dynamics can be understood in terms of the well-known elastic interspecies s-wave scattering length. Inelastic three-body collisions are studied with atomic resolution, allowing to unambiguously assign losses to Rb-Rb-Cs three-body recombination and permitting a precise determination of the loss coefficient, which is not directly possible in balanced mixtures. In all experiments, the ultracold Rb gas remains unaffected by the interaction with the Cs impurity atoms, demonstrating the feasibility of using single atoms as probes for a many-body system. The obtained results for the interaction properties of the two sub-systems are a significant step toward a coherently interacting hybrid system of individually controllable impurities in a quantum many-body system.

Host: 
Saffman
Speaker: Nicolas Spethmann Institute for Applied Physics, University of Bonn

 

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Room and Building: 
5310 Chamberlin

Feedback loops are central in most classical control procedures. A controller compares the signal measured by a sensor with the target value. It then adjusts an actuator to bring the signal close to the target value. Generalizing this scheme to the quantum world must overcome a fundamental difficulty: the sensor measurement causes a random back-action on the system. I will present how we have been able to continuously operate a quantum feedback loop stabilizing photon number states in a very high finesse Fabry-Perot cavity. Circular Rydberg atoms repeatedly achieve weak quantum non-demolition measurements of the photon number. A classical computer estimates in real-time the density matrix of the field, based on the outcome of these measurements, and taking into account all known experimental imperfections. It then calculates the amplitude of small classical microwave fields injected into the cavity to bring the field into the target state. We have been able to prepare on demand and stabilize Fock states containing from 1 to 4 photons. This achievement opens interesting perspectives for the production and control of non-classical states for quantum information processing.

Host: 
Mark Saffman
Speaker: Clément Sayrin Laboratoire Kastler Brossel, l'Ecole Normale Supérieure

 

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Room and Building: 
5310 Chamberlin
The quantum computing community is making evermore progress towards constructing a fully functional quantum computer. However, none of the many approaches in the different fields of physics have succeeded to date. In the neutral atom quantum computing approach, which uses atoms trapped by light fields as quantum bits (qubits), many of the requirements for a quantum computer (initialization, readout, single-qubit gates) can be met with well-established spectroscopic techniques. The recent accomplishment of two-qubit gates with neutral atoms leaves only one unattained criterion for a quantum computer: The ability to create an addressable array of many qubits.

We will present computational results on a possible solution to this problem. The diffraction pattern formed by laser light incident on a circular aperture exhibits localized bright and dark spots that can be used as atomic dipole traps. An array of such apertures results in a two-dimensional array of dipole traps that can be individually addressed with a laser beam from the third dimension. By exploiting the polarization dependence of these traps, we can also bring traps together and apart to facilitate the performance of two-qubit gates, thus creating a potential candidate for a scalable quantum memory for a neutral atom quantum computer.
Host: 
Saffman
Speaker: Katharina Gillen California Polytechnic State University

 

Available Downloads:

Room and Building: 
5310 Chamberlin
Host: 
Walker
Speaker: Tony Tong Oak Ridge National Laboratory

 

Available Downloads:

Room and Building: 
5280 Chamberlin

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