Atomic Physics Seminar

Optical atomic magnetometers are among the most precise magnetic sensors today, reaching sensitivities up to 0.16 fT/sqrt(Hz). While the AC Stark effect is one of the noise sources in atomic magnetometers, it can be utilized to improve these devices. The effect of the vector part of the AC Stark operator on alkali atoms is equivalent to applying a magnetic field in the direction of the light propagation. We use this effect to create an all-optical vector magnetometer with 0.2 pT/sqrt(Hz) sensitivity to the field magnitude and 4 mrad/sqrt(Hz) sensitivity to the field direction, as well as a scalar magnetometer driven by a fictitious rf field with 40 fT/sqrt(Hz) sensitivity.

Host: 
Walker
Speaker: Lena Zhivun Berkeley

 

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Room and Building: 
5310 Chamberlin

TBD

Host: 
Walker
Speaker: Dr. Stephen Kadlecek University of Pennsylvania

 

Available Downloads:

Room and Building: 
5280 Chamberlin Hall

Atomic Hong-Ou-Mandel effect: a mile-stone in Quantum Atom Optics

Host: 
Walker
Speaker: Alain Aspect Institut d’Optique

 

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Room and Building: 
5310 Chamberlin Hall
An alternative framework to quantum information and computation based on spin coherent states is proposed. Traditionally quantum computing approaches are formulated in terms of either discrete (qubit) or continuous variables. Our approach offers an alternative third path, naturally suited towards implementations in cold atom ensembles and BECs. The scheme is illustrated by an application to quantum algorithms and we discuss the effects of decoherence induced by the large number of particles in the BEC. In particular, we discuss a quantum teleportation protocol that allows for the transfer of spin coherent states beyond the usual continuous variables formalism. The scheme differs from existing protocols in that a large ensemble of spins is teleported, rather than a qubit variable, resulting in a type of macroscopic teleportation. Other techniques such as phase contrast imaging and Deutsch-Jozsa algorithm in a beyond continuous variables context are also discussed.
Host: 
Saffman
Speaker: Tim Byrnes NYU

 

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Room and Building: 
5310 Chamberlin
Host: 
Yavuz
Speaker: various various

 

Available Downloads:

Room and Building: 
2241 Chamberlin Hall
Photons are the perfect "flying qubits" for quantum communication: they travel at the speed of light and have only weak nonlinear interactions with their environment. While these features make photons ideal carriers of quantum information, many quantum communication protocols require qubits to interact in quantum logic gates. Although interactions between individual photons are too weak for reliable multi-qubit gates, it is relatively easy to implement efficient gates between different degrees of freedom encoded on the same photon. By using photons that are simultaneously entangled in multiple degrees of freedom ("hyperentangled") we can perform operations that are impossible for single-qubit states, as well as gain access to higher dimensional entanglement. We demonstrate that hyperentangled states can be used for efficient quantum state communication, increased classical channel capacity, and more efficient quantum channel characterization.
Host: 
Saffman
Speaker: Trent Graham Urbana-Champaign

 

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Room and Building: 
5310 Chamberlin Hall

Coulomb interactions limit the brightness of charged particle beams. Controlling the effects of nonlinear beam expansion (space charge) and disordered inter-particle scattering is of critical importance for applications ranging from ultrafast electron diffraction to injectors for particle accelerators. In this talk I will show that ultra-cold ion bunches extracted from laser-cooled atoms can be used to observe the effects of Coulomb interactions with unprecedented detail. Arbitrarily shaped bunches are created to reverse the space-charge problem, and excitation of the cold atoms to Rydberg states prior to ionisation reduces the disorder-induced heating effect. I will present our experimental results that demonstrate improved beam brightness and models and simulations of the effects.

Host: 
Saffman
Speaker: Dene Murphy University Melbourne

 

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Room and Building: 
5310 Chamberlin Hall

Conventional methods of quantum simulation rely on kinectic energy determined by free particle dispersions or simple sinusoidal optical lattices. Solid state sytems, by contrast, exhibit a plethora of band structures which differ quantitatively, qualitatively, and even topologically. To what extent does this variety explain the many electronic phenomena observed in these materials? Here we address this question by subjecting an otherwise simple Bose superfluid to a customized band structure engineered by dynamically phase modulating (shaking) an optical lattice. The engineered dispersion contains two minima which we associate to a pseudospin degree of freedom. Surprisingly, in such a system the Bose superfluid exhibits many new behaviors. The psuedospin develops a ferromagnetic order, which can lead to polarization of the entire sample or to sub-division into polarized domains. The excitations of the system also exhibit the roton-maxon structure associated with strong interactions in superfluid helium.

Host: 
Coppersmith
Speaker: Colin Parker University of Chicago, James Franck Institute and Department of Physics

 

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Room and Building: 
4274 Chamberlin Hall
We present results on our Cs ultracold Rydberg atom experiments involv-<br>
ing two classes of ultralong-range Rydberg molecules known as trilobite&quot; and<br>
butter<br>
y&quot; molecules. These molecules are predicted to have giant, body-xed<br>
permanent dipole moments on the order of 1000 Debye. The two classes of<br>
molecules are distinguished by the relative dominance of the s-wave and p-wave<br>
electron scattering. We present spectra for (nS1=2 +6S1=2)3 molecules, where<br>
n = 37, 39 and 40, and measurements of the Stark broadenings of selected<br>
trilobite states in Cs due to the application of a constant external electric eld.<br>
Additionally, we present measurements of spectra and Stark splittings for p-<br>
wave dominated (nS1=2 + 6S1=2)3 molecules, where n = 31 and 32.<br>
Host: 
Saffman
Speaker: Donald Booth University of Oklahoma

 

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Room and Building: 
5310 Chamberlin
Trapped ions are qubit standards in quantum information science because of their long coherence times and high fidelity entangling gates controlled with external fields. Scaling to very large dimensions may require the use of a modular architecture where trapped ions in separate ion trap modules are entangled using a photonic interface while ions in the same module are entangled using a phonon bus. We report the successful combination of these types of entanglement within and between two modules. We use fast optics to generate heralded remote entanglement between modules at rates exceeding 4 per second, faster than the experimentally measured decoherence rate of the remote entangled state. The resource scaling in such a modular architecture is super-exponential in the ratio of the mean remote entanglement time to the entangled qubit coherence time, and trapped ions are the only experimental system to date where this ratio is small and the overhead is not forbidding.<br>
<br>
Modular quantum networks may involve the use of different types of qubits to create a large scale network. Heralded entanglement between qubits using photon interference is a powerful tool to create entanglement within heterogeneous quantum systems. We experimentally demonstrate the entanglement of non-identical qubits by interfering distinguishable photons emitted from distinguishable trapped ions without significant loss of remote entanglement rate or fidelity.
Host: 
Saffman
Speaker: David Hucul University of Maryland

 

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Room and Building: 
5310 Chamberlin

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