Bose-Einstein condensation (BEC) has been observed in a dilute gas of sodium atoms. A Bose-Einstein condensate consists of a macroscopic population of the ground state of the system, and is a coherent state of matter. In an ideal gas, this phase transition is purely quantum-statistical. The study of BEC in weakly interacting systems which can be controlled and observed with precision holds the promise of revealing new macroscopic quantum phenomena that can be understood from first principles.

Bose-Einstein condensation in a gas of sodium atoms

Fermionic alkaline-earth atoms have unique properties that make them attractive candidates for the realization of atomic clocks and degenerate quantum gases. At the same time, they are attracting considerable theoretical attention in the context of quantum information processing. Here we demonstrate that when such atoms are loaded in optical lattices, they can be used as quantum simulators of unique many-body phenomena. In particular, we show that the decoupling of the nuclear spin from the electronic angular momentum can be used to implement many-body systems with an unprecedented degree of symmetry, characterizedbytheSU(N)groupwithNaslargeas10.Moreover,theinterplayofthenuclearspinwiththeelectronicdegreeof freedomprovidedbyastableopticallyexcitedstateshouldenablethestudyofphysicsgovernedbythespin‐orbitalinteraction. Such systems may provide valuable insights into the physics of strongly correlated transition-metal oxides, heavy-fermion materials and spin-liquid phases.

/pdf/two-orbital-su-n-magnetism-with-ultracold-alkaline-earth-3ap4dtx7sn.pdf

Two-orbital SU(N) magnetism with ultracold alkaline-earth atoms

Quantum optics: Dedication

Optical resonance and two-level atoms

Physicists have used cold atomic gases to simulate quantum phenomena that we normally associate with much more complex systems, such as solid-state materials. Because the properties of these gases are so tunable, it is also possible to create conditions that otherwise do not exist in nature. Zhang et al. studied an exotic type of magnetism in an array of pancake-shaped atomic clouds of 87Sr. They prepared the atoms' nuclei in different combinations of 10 quantum states. They then shone pulses of light at the atoms to deduce the properties of the atoms' interactions. The interactions were independent of the atoms' nuclear states—a hallmark of an unusual symmetry that theorists predict may lead to interesting collective effects.

Science , this issue p. [1467][1]

 [1]: /lookup/doi/10.1126/science.1254978

/pdf/spectroscopic-observation-of-su-n-symmetric-interactions-in-ef2a3mm5bu.pdf

Spectroscopic observation of SU(N)-symmetric interactions in Sr orbital magnetism

We present a unique confocal microscope capable of measuring the Raman and Brillouin spectra simultaneously from a single spatial location. Raman and Brillouin scattering offer complementary information about a material’s chemical and mechanical structure, respectively, and concurrent monitoring of both of these spectra would set a new standard for material characterization. We achieve this by applying recent innovations in Brillouin spectroscopy that reduce the necessary acquisition times to durations comparable to conventional Raman spectroscopy while attaining a high level of spectral accuracy. To demonstrate the potential of the system, we map the Raman and Brillouin spectra of a molded poly(ethylene glycol) diacrylate (PEGDA) hydrogel sample in cyclohexane to create two-dimensional images with high contrast at microscale resolutions. This powerful tool has the potential for very diverse analytical applications in basic science, industry, and medicine.

Dual Raman-Brillouin Microscope for Chemical and Mechanical Characterization and Imaging

Over the years, light scattering from acoustic waves has grown to be increasingly important in the fields of biology and medicine. This type of scattering, known as Brillouin scattering, has already seen a plethora of applications in fields such as physics. However, the potential for Brillouin scattering for medical imaging and diagnostics has only recently been considered. In this work, we summarize most of the applications of Brillouin scattering in biology to date, and some current work in our lab showing how Brillouin scattering is a worthy prospect for many emerging problems in biology and medical diagnostics.

Seeing cells in a new light: a renaissance of Brillouin spectroscopy

Brillouin spectroscopy is an emerging tool for microscopic optical imaging as it allows for non-contact, non-invasive, direct assessment of the elastic properties of materials. However, strong elastic scattering and stray light from various sources often contaminate the Brillouin spectrum. A molecular absorption cell was introduced into the virtually imaged phased array (VIPA) based Brillouin spectroscopy setup to absorb the Rayleigh component, which resulted in a substantial improvement of the Brillouin spectrum quality.

Background clean-up in Brillouin microspectroscopy of scattering medium.

We present results from two-photon photoassociative spectroscopy of the least-bound vibrational level of the $X\phantom{\rule{0.2em}{0ex}}^{1}\ensuremath{\Sigma}_{g}^{+}$ state of the $^{88}\mathrm{Sr}_{2}$ dimer. Measurement of the binding energy allows us to determine the $s$-wave scattering length ${a}_{88}=\ensuremath{-}1.4(6){a}_{0}$. For the intermediate state, we use a bound level on the metastable $^{1}S_{0}\text{\ensuremath{-}}^{3}P_{1}$ potential, which provides large Franck-Condon transition factors and narrow one-photon photoassociative lines that are advantageous for observing quantum-optical effects such as Autler-Townes resonance splittings.

/pdf/two-photon-photoassociative-spectroscopy-of-ultracold-sr-88-5503s3en8g.pdf

Two-photon photoassociative spectroscopy of ultracold Sr 88

Two-dimensional stimulated Brillouin scattering microscopy is demonstrated for the first time using low power continuous-wave lasers tunable around 780 nm. Spontaneous Brillouin spectroscopy has much potential for probing viscoelastic properties remotely and non-invasively on a microscopic scale. Nonlinear Brillouin scattering spectroscopy and microscopy may provide a way to tremendously accelerate the data aquisition and improve spatial resolution. This general imaging setup can be easily adapted for specific applications in biology and material science. The low power and optical wavelengths in the water transparency window used in this setup provide a powerful bioimaging technique for probing the mechanical properties of hard and soft tissue.

/pdf/stimulated-brillouin-scattering-microscopic-imaging-azqpscqge6.pdf

Andrew J. Traverso

Papers

Dual Raman-Brillouin Microscope for Chemical and Mechanical Characterization and Imaging

Seeing cells in a new light: a renaissance of Brillouin spectroscopy

Background clean-up in Brillouin microspectroscopy of scattering medium.

Two-photon photoassociative spectroscopy of ultracold Sr 88

Stimulated Brillouin Scattering Microscopic Imaging.