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Nathan Gemelke

Publications and source records attributed to Nathan Gemelke.

23 records · Page 2Linked to original sources
arXiv2008

Ultracold molecules: vehicles to scalable quantum information processing

We describe a novel scheme to implement scalable quantum information processing using Li-Cs molecular state to entangle $^{6}$Li and $^{133}$Cs ultracold atoms held in independent optical lattices. The $^{6}$Li atoms will act as quantum bits to store information, and $^{133}$Cs atoms will serve as messenger bits that aid in quantum gate operations and mediate entanglement between distant qubit atoms. Each atomic species is held in a separate optical lattice and the atoms can be overlapped by translating the lattices with respect to each other. When the messenger and qubit atoms are overlapped, targeted single spin operations and entangling operations can be performed by coupling the atomic states to a molecular state with radio-frequency pulses. By controlling the frequency and duration of the radio-frequency pulses, entanglement can either be created or swapped between a qubit messenger pair. We estimate operation fidelities for entangling two distant qubits and discuss scalability of this scheme and constraints on the optical lattice lasers.

quant-ph↗
arXiv2008

Exploring Universality of Few-Body Physics Based on Ultracold Atoms Near Feshbach Resonances

A universal characterization of interactions in few- and many-body quantum systems is often possible without detailed description of the interaction potential, and has become a defacto assumption for cold atom research. Universality in this context is defined as the validity to fully characterize the system in terms of two-body scattering length. We discuss universality in the following three contexts: closed-channel dominated Feshbach resonance, Efimov physics near Feshbach resonances, and corrections to the mean field energy of Bose-Einstein condensates with large scattering lengths. Novel experimental tools and strategies are discussed to study universality in ultracold atomic gases: dynamic control of interactions, run-away evaporative cooling in optical traps, and preparation of few-body systems in optical lattices.

cond-mat.other↗
arXiv2008

Fast, Runaway Evaporative Cooling to Bose-Einstein Condensation in Optical Traps

We demonstrate a simple scheme to achieve fast, runaway evaporative cooling of optically trapped atoms by tilting the optical potential with a magnetic field gradient. Runaway evaporation is possible in this trap geometry due to the weak dependence of vibration frequencies on trap depth, which preserves atomic density during the evaporation process. Using this scheme, we show that Bose-Einstein condensation with ~10^5 cesium atoms can be realized in 2~4 s of forced evaporation. The evaporation speed and energetics are consistent with the three-dimensional evaporation picture, despite the fact that atoms can only leave the trap in the direction of tilt.

cond-mat.other↗
arXiv1999

On the relative positions of the $2Δ$ peaks in Raman and tunneling spectra of d-wave superconductors

We study $B_{1g}$ Raman intensity $R(Ω)$ and the density of states $N(ω)$ in isotropic 2D d-wave superconductors. For an ideal gas, $R(Ω)$ and $N(ω)$ have sharp peaks at $Ω=2Δ$ and $ω=Δ$, respectively, where $Δ$ is the maximum value of the gap. We study how the peak positions are affected by the fermionic damping due to impurity scattering. We show that while the damping generally shifts the peak positions to larger frequencies, the peak in $R(Ω)$ still occurs at almost twice the peak position in $N(ω)$ and therefore cannot account for the experimentally observed downturn shift of the peak frequency in $R(Ω)$ in underdoped cuprates compared to twice that in $N(ω)$. We also discuss how the fermionic damping affects the dynamical spin susceptibility.

cond-mat.supr-con↗