Kutztown University Department of Physics

My reasearch has spanned multiple areas of physics over the years. A brief overview is given below for each, along with a couple of representative papers. While I am not actively working on some of these topics at the present, they all continue to influence and guide my current research interests. Specifically, the diversity of topics has been indispensible for my long term research on the foundations of modern physics, not described here, but on which I expect to publish soon.

Recent work has focussed on quantum teleportation. A general algorithm was developed based on machine-learning to generate quantum teleportation of arbitrary single and multi-particle states with optimal fidelity. Further improvement of fidelity has been accomplished with multi-state optimization and adaptive measurements. Another important issue that has been addressed is creating well-defined benchmarks to distinguish quantum teleportation from classical counterparts that do not use entanglement. Most established benchmarks only work for teleporting states chosen from an uniform distribution. We have developed rigorous benchmarks that can be applied to teleportation of states that follow non-uniform prior distributions as well. On another front, since much of quantum technology depends on entanglement generation, a recent paper examines how maximal entanglement could be generated between collective spin states of two distinct species of interacting coherent atoms.

Starting with my doctoral thesis work on Bose-Einstein-condenstate (BEC), I have been interested in the nonlinear Schrödinger equation (NLSE) which provides the mean-field description of interactions. In recent years, with the help of several students, I have done a comprehensive study of the NLSE with both open and ring-shaped boundary conditions. We developed a unified description of 1D quantum scattering in the presence of interactions, in terms of a single Jacobi elliptic function with a complex phase. This work hs led to a new way for describing scattering of ineracting systems with stationary states. In other work, comprehensive spectrum of stationary states of a NLSE has been determied for a BEC trapped in a ring-shaped lattice, for both positive and negative nonlinearities. I have also been interested in interacting quantum systems that use a full quantum description, such as the Bose-Hubbard model. A recent paper showed novel finite size features in small systems of bosons trapped in just a few lattice sites, which vanish in the thermodynamic limit.

Ultracold atoms have become the go-to simulators for quantum phenomena since it scales up quantum behavior from the scale of elementrary particles to conglomerations of millions of atoms, as in a BEC. That allows utilizing quantum effects to push the sensitivity of sensors, particularly since matter waves have much shorter wavelengths than typical lasers. Much of my recent work has been in developing ideas for different simulators and sensors using ultracold atoms. I have had two US patent awards for a new principle based on localization rather than inteferometry, for high-precision sensors for rotation and magnetic field. Some recent papers have put forward mechanisms to simulate spin-orbit and hyperfine structrues, to implement the Lipkin-Meshkov-Glick model, and to study nonlinear phase transitions and spin squeezing, all using interacting ultracold atoms in ring traps.

In the field of ultracold atoms, one of the most significant innovations has been the ability to create features that emulate the behavior of charged particles in the presence of a magnetic field, via a clever use of geometric phase. This continues to be an area of active interest for me due to its ties to gauge theory. I have written a paper on how the quintessential Harper model can be simulated with ultracold atoms in a ring trap. I have extended those ideas to two-dimensional lattice systems with non-trivial topology, including a cylindrical lattice and a toroidal lattice. I have also shown how Wilson loops can be used to characterize trully non-Abelian gauge structures created synthetically, and I proposed a new diamond scheme for creating degenerate dark states that are essential for creating synthetic gauge fields with cold atoms.

Coherent Transport Adiabatic Passage (CTAP)is an almost magical quantum effect whereby material entities like atoms and electrons can be transferred from one potential well to a non-adjacent potential well without ever having any significant presence in an intervening well. Although it looks on the surface like 'teleportation', it is actually the spatial analog of the well know effect known as Stimulated Raman Adiabatic Passage (STIRAP). I wrote several papers on this phenomenon in the context of ultracold atoms, mostly with my long term collaborator Tomáš Opatrný, where we identified optimal transfer conditions, generalized to dual interacting species transport without the two species ever overlapping, and designed an atomtronics version of a transistor operation with neutral atoms carriers instead of electrons and holes.

My interest in mesoscopic transport started during my post-doc at Penn State. I used the Landauer-Büttiker formalism extensively to model transport in nanowires, which are treated as quasi 1D waveguides with different transverse energies acting as distinct channels, and the current driven by the difference in chemical potential. I wrote several papers on adiabatic quantum pumps, in the context of nanoscale transport, and on characterizing mobility in nanowires. This brought me into the general realm of nano-technology, which has been quite useful over the years. Later, I realized that the same physical setup could be translated to cold atomic systems and wrote a paper on it, specifically suggeting routes to implementing quantum pumps using atom-chips technology. A version of it was subsequently implemented in experiments in the lab of my collaborator, Seth Aubin who was also a coauthor on that initial proposal. I wrote a few other papers on various types of qauntum pumping mechanisms, involving different types of time-varying potentials. Movies related to a paper on a paddlewheel pump mechanism can be found at: A Quantum Paddlewheel

I have applied stochastic calculus to study both quantum and classical systems. The underlying principles are universal in the sense that they can be applied to all arenas of study including physics, biology and economics, which have noise or randomness in them. My work has utilized both Langevin and Fokker-Planck approaches. In the quantum regime, I worked with Girish Agarwal, an authority in the field, on a Langevin analyis of fundamental noise limits in some aspects of Coherent Anti-Stokes Raman spectroscopy. On the classical side, I published on stochastic properties of Photoacoustic Raman spectroscopy, and also on calcium signalling in the context of ion channels in biological cells.

In the process of studying quantum pumps, and general quantum scattering by time-varying potentials, a comparision with clasical scattering naturally led to bridging of the two limits via semiclassical theory. This lead to several interesting papers with collaborators Seth Aubin and John Delos at The College of William & Mary, and Kevin Mitchell from UC Merced. Specfically, the semiclassical theory gave excellent agreement with the structure of the Floquet side-bands intrisic to scattering by time-dependent potentials.

I wrote several papers on ultracold atoms in 1D, particularly during my postdoctoral years in the Optical Sciences Center working with Marvin Girardeau, who was a pioneer in this field. In those papers, I explore Bose-Fermi mixtures in 1D, and crossover from 1D to 3D, and interference effects. My experience with 1D systems was later useful for studying mesoscopic transport in nanowires, and ultracold atoms in quasi-1D ring traps.

My doctoral work was on the static and dynamical properties of BEC. I studied the evolution and damping of BEC, and examined how highly anistropic BEC's crossover from 3D to 2D and 1D. In recent years, I have been interested in the properties of BEC in configurations with non-trivial topology. Wrapping degenerate ultracold atoms around ring shaped traps can make the non-local quantum effects directly manifest in the macroscopic quantum states. An azimuthal lattice makes the system both more interesting and in some ways simpler by introducing a new length scale. Such coherent systems allow a wide range of quantum mechanical effects to be investigated.