Groups | Seminars || Courses | Outreach


Seminars will be held held at room S-141 in the Physics and Astronomy Department building on Mondays at 3:00 PM, unless noted otherwise.


Fall 2016

September 19, 2016

Prof. Jiannis Pachos
University of Leeds, UK

Majorana fermions in a photonic quantum simulator

(Host: Dominik Schneble)

The realization of Majorana fermions is in the centre of intense theoretical and experimental investigations. Unfortunately, their exchange that can reveal their exotic statistics needs manipulations that are still beyond our experimental capabilities. In this pedagogical talk I will present an alternative approach to this problem. Through the Jordan-Wigner transformation, the Kitaev’s chain supporting two Majorana fermions can be mapped to the Ising spin-1/2 chain. We experimentally simulated the spin system and its evolution with a photonic quantum simulator. By studying the induced geometric phases we were able to simulate the exchange of two Majoranas positioned at the ends of a three-site chain. the immunity of the topologically encoded quantum information is also demonstrated  against local errors. 

September 26, 2016

Andreas Schindewolf
University of Innsbruck, Austria

Quantum Engineering of a low-entropy gas of RbCs molecules in an optical lattice

(Host: Dominik Schneble)

Quantum many-body systems with long-range dipolar interaction are currently of immense interest in the theory and experiment community. Until recently, experimental realization with dipolar molecules was unfeasible due to high sample entropy. We present a novel method to prepare low-entropy samples of molecules as an ideal starting point for such experiments [1].

Starting from two spatially separated BECs, we form Rb-Cs precursor pairs by overlapping a Cs Mott insulator with superfluid Rb in an optical lattice. For this purpose, the Rb-Cs interaction is nulled at a Feshbach resonance's zero crossing. After the Rb atoms are localized by further enhancing the lattice depth, the paired atoms are associated to Feshbach molecules by means of the aforementioned Feshbach resonance. With this method we produce a low-entropy molecular sample with a filling fraction exceeding 30%.

Combining the method with a STIRAP technique to produce dipolar ground-state molecules, which we already realized with 90% efficiency [2], we will be able to address experiments in the context of dipolar many-body physics.

[1] arXiv:1607.06536
[2] Phys. Rev. Lett. 113, 263201 (2014)

October 6, 2016
(Thurs, 4pm in SCGP-102)

Prof. Maxim Olshanii
University of Massachusetts Boston

Quantum Galilean Cannon as a Schrödinger Cat

SCGP Workshop: Entanglement in Quantum Systems

[SCGP workshop]

October 14, 2016 (Fri, 3pm)

Dr. Oleg Pronin
MPQ Garching, Germany

High-power femtosecond thin-disk oscillators for mid-infrared and extreme ultraviolet generation

(Host: Tom Allison)

Recent advances in the development of femtosecond thin-disk oscillators are reported. A novel mode-locking technique relying on distributed Kerr-lenses is presented. The generation of W-level mid-infrared frequency comb is described.


October 19, 2016 (Wed)

Krupa Ramasesha
Sandia National Laboratory

Condensed phase vibrational and electron dynamics probed using ultrafast nonlinear spectroscopy

(Host: Tom Allison)

This talk will present ultrafast spectroscopic investigations of condensed phase dynamics on attosecond to picosecond timescales. The first part will discuss coherent two-dimensional infrared (2D IR) spectroscopy of hydrogen bonding and vibrational dynamics in liquid water, where experimental evidence of large angle reorientation responsible for inertial hydrogen bond switching was observed, and evidence of highly coupled intra- and inter-molecular vibrations of liquid water was seen, resulting in rapid and efficient energy dissipation. The second part will focus on attosecond extreme ultraviolet spectroscopy of electron dynamics in silicon, where evidence for strong field tunneling of electrons across the band gap, carrier-carrier interaction, band gap renormalization and field-induced shifts were observed.

October 24, 2016

Sergei Nazarenko and Chris Presuto

Photonics Industries International, Inc.

Technology and Applications of Diode Pumped Solid State Picosecond Lasers

(Host: Hal Metcalf)

Two Stony Brook Physics alumni discuss their work at Photonics Industries International, a local company that is innovating advances in the growing field of picosecond pulsed DPSS lasers. This will be an overview of the current cutting edge of industrial laser technology, including picosecond pulse generation, amplification, and nonlinear frequency conversion. We will also discuss current laser applications in industry and research, and discuss some of the challenges faced when bringing an idea from a test-bench to a mass producible manufactured product.

November 1, 2016
(Tues, 4pm in Harriman-137)

Prof. Thomas Killian
Rice University

Studying Collisions and Transport in Strongly Coupled Systems with Ultracold Plasmas

Physics & Astronomy Colloquium

Ultracold neutral plasmas, formed by photoionizing laser-cooled atoms near the ionization threshold, explore matter at the intersection of atomic, soft condensed matter, and plasma physics. Because of the low electron and ion temperatures (Te=1-1000K and Ti=1K), the Coulomb interaction energy per particle can exceed the thermal energy, which makes the system strongly coupled. Strong coupling is of interest in many areas of physics. It leads to spatial correlations and surprising equilibration dynamics, and it makes theoretical description much more difficult. Ultracold plasmas provide a valuable window into these phenomena because of the excellent control of initial conditions and diagnostics that are available. I will describe recent results that give the first measurement of equilibration rates [1] and diffusion coefficients in the strongly coupled regime [2], which are relevant for plasmas produced through short-pulse laser irradiation of solid targets, such as in inertial confinement fusion. The dynamics also shows non-Markovian or memory effects that are reminiscent of the behavior of metal liquids.

[1] “Velocity Relaxation in a Strongly Coupled Plasma,” G. Bannasch, J. Castro, P. McQuillen, T. Pohl and T. C. Killian, Phys. Rev. Lett. 109, 185008 (2012).

[2] “Experimental Measurement of Self-Diffusion in a Strongly Coupled Plasma,” T. S. Strickler, T. K. Langin, P. McQuillen, J. Daligault, and T. C. Killian, Phys. Rev. X 6, 021021 (2016).

November 2, 2016 (Wed, 3pm)

Prof. Thomas Killian
Rice University

From Ultralong-range Molecules to Rydberg Polarons in a Bose Gas

(Host: Hal Metcalf/Dominik Schneble)

Rydberg atoms excited in a dense gas interact very strongly with background, ground-state atoms that lie within the Rydberg orbital. This problem has a long history, and it inspired Fermi to develop the Fermi pseudo-potential to describe the low-energy scattering of a Rydberg electron and ground-state atoms. With the availability of ultracold atomic gases, this topic has received renewed interest.

I will describe the excitation of Rydberg atoms in a Bose-Einstein condensate of strontium atoms. In a few-body regime, we observe a dense, highly structured spectrum reflecting excitation of ultralong-range molecules consisting of one or more ground-state atoms bound to the Rydberg core in potential wells formed by the Rydberg-electron wave function. This represents a new molecular bonding mechanism and novel ultacold chemistry. In a many-body regime, with hundreds of ground-state atoms within the Rydberg orbital, the Rydberg atoms can be viewed as an impurity in a quantum gas, connecting to important concepts in condensed matter physics. The spectrum for impurity excitation displays signatures of polaronic states, in which the Rydberg atom significantly perturbs the density of the background Bose gas.

In the low energy range probed in these experiments, the scattering of electrons from ground-state strontium atoms lacks a p-wave resonance. Such a resonance plagues alkali atoms that have previously been used to study Rydberg excitation in dense, ultracold gases. This leads to enhanced Rydberg-atom/molecule lifetime for strontium, and is critical for modelling the spectrum in the many-body regime and probing the physics of polarons.

November 4, 2016
(1:30pm in B-141)

Prof. Fabio Franchini
Ruder Boskovic Inst.- Zagreb, Croatia

Universal Dynamics of a localized excitation after an interaction quench

Condensed-matter physics seminar

[CMP seminar page]

November 7, 2016
(2:30pm in SCGP-313)

Prof. Andrea Trombettoni
SISSA-Trieste, Italy

Tunneling-based quantum devices with ultracold strongly interacting atoms

SCGP Program: Entanglement and Dynamical Systems

[SCGP program]

November 21, 2016

Dr. Leland Aldridge
University of Connecticut

The Bichromatic Force in Multi-Level Systems

(Host: Hal Metcalf)

The optical bichromatic force (BCF) has been previously demonstrated, in two-level atomic systems, to produce forces significantly in excess of the maximum achievable radiative or photon scattering force. Its application to multilevel systems has been less well understood. I present examinations of BCF in various simple multilevel systems, which inform prescriptions for the application of the BCF to general multilevel systems. I apply these prescriptions to simulations of the molecular systems CaF and SrOH and show that BCF is feasible in these molecules, and discuss planned experiments to measure BCF deflection of a molecular beam of CaF.