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Search Publications by: Charles W Clark (Assoc)

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Displaying 26 - 50 of 226

Quantum Key Distribution System Operating at Sifted-Key Rate Over 4 Mbit/s 1

June 1, 2009
Author(s)
Xiao Tang, Lijun Ma, Alan Mink, Anastase Nakassis, Hai Xu, Barry J. Hershman, Joshua C. Bienfang, David H. Su, Ronald F. Boisvert, Charles W. Clark, Carl J. Williams
A complete fiber-based polarization encoding quantum key distribution (QKD) system based on the BB84 protocol has been developed at National Institute of Standard and Technology (NIST). The system can be operated at a sifted key rate of more than 4 Mbit/s

Topological Insulators and Metals in Atomic Optical Lattices

May 28, 2009
Author(s)
Tudor Stanescu, Victor Galitski, Jay Vaishnav, Charles W. Clark, Sankar Das Sarma
We propose the realization of topological quantum states with cold atoms trapped in an optical lattice. We discuss an experimental setup that generates a two-dimensional hexagonal lattice in the presence of a light-induced periodic vector potential, which

Measurement of Small Birefringence and Loss in a Nonlinear Single-mode Waveguide

May 11, 2009
Author(s)
Daniel Rogers, Charles W. Clark, Christopher Richardson, Julius Goldhar
We design and fabricate a birefringent semiconductor waveguide for application to nonlinear photonics, demonstrating that it is possible to engineer a small birefringence into such a device using multiple core layers. We also demonstrate a simple technique

Phase transitions, entanglement and quantum noise interferometry in cold atoms

March 5, 2009
Author(s)
F. Mintert, A.M. Rey, Indubala I. Satija, Charles W. Clark
We show that entanglement monotones can characterize the pronounced enhancement of entanglement at a quantum phase transition if they are sensitive to long-range high order correlations. These monotones are found to develop a sharp peak at the critical

Creating a supersolid in one-dimensional Bose mixtures

January 15, 2009
Author(s)
Ludwig G. Mathey, Ippei Danshita, Charles W. Clark
We identify a one-dimensional supersolid phase in a binary mixture of near-hardcore bosons with weak, local interspecies repulsion. We find realistic conditions under which such a phase, defined here as the coexistence of quasi-superfluidity and quasi

Non-quantization of Current in an Annular Bose-Einstein Condensate

October 16, 2008
Author(s)
D L. Feder, L A. Collins, Charles W. Clark
The circulating states of a Bose-Einstein condensate confined in an annulus are investigated both analytically and numerically. It is demonstrated that while single-valuedness of the condensate wavefunction ensures the quantization of circulation in this

Quantum key distribution at GHz transmission rates

February 11, 2008
Author(s)
Alessandro Restelli, Joshua C. Bienfang, Alan Mink, Charles W. Clark
Quantum key distribution (QKD) channels are typically realized by transmitting and detecting single photons, and therefore suffer from dramatic reductions in throughput due to both channel loss and noise. These shortcomings can be mitigated by applying

Pseudo-Fermionization of 1-D Bosons in Optical Lattices

February 2, 2008
Author(s)
G Pupillo, A M. Rey, Carl J. Williams, Charles W. Clark
We present a model that generalizes the Bose-Fermi mapping for strongly correlated 1D bosons in an optical lattice, to cases in which the average number of atoms per site is larger than one. This model gives an accurate account of equilibrium properties of

Magic Wavelengths for the np - ns Transitions in Alkali-Metal Atoms

November 15, 2007
Author(s)
B Arora, M S. Safronova, Charles W. Clark
Extensive calculations of the electric-dipole matrix elements in alkali-metal atoms are conducted using the relativistic all-order method. This approach is a linearized version of the coupled-cluster method, which sums infinite sets of many-body

Quantum Phases of Bosons in Double-Well Optical Lattices

October 4, 2007
Author(s)
Ippei Danshita, J G. Williams, Carlos Sa de Melo, Charles W. Clark
We study the superfluid to Mott insulator transition of bosons in a two-legged ladder optical lattice, of a type accessible in current experiments on double-well optical lattices. The zero-temperature phase diagram is mapped out, with a focus on its

Detector Dead-Time Effects and Paralyzability in High-Speed Quantum Key Distribution

September 10, 2007
Author(s)
Daniel Rogers, Joshua C. Bienfang, Anastase Nakassis, Hai Xu, Charles W. Clark
Recent advances in quantum key distribution (QKD) have given rise to systems that operate at transmission periods significantly shorter than the dead times of their component single-photon detectors. As systems continue to increase in transmission rate

Metal-Insulator Transition Revisited for Cold Atoms in Non-Abelian Gauge Potentials

November 20, 2006
Author(s)
Indubala I. Satija, D C. Dakin, Charles W. Clark
We discuss the possibility of realizing metal-insulator transitions with ultracold atoms in two-dimensional optical lattices in the presence of artificial gauge potentials. Such transitions have been extensively studied for magnetic fields corresponding to

Demonstration of an Active Quantum Key Distribution Network

August 1, 2006
Author(s)
Xiao Tang, Lijun Ma, Alan Mink, Anastase Nakassis, Hai Xu, Barry J. Hershman, Joshua Bienfang, David H. Su, Ronald Boisvert, Charles W. Clark, Carl J. Williams
We previously demonstrated a high speed, point to point, quantum key distribution (QKD) system with polariztion coding over a fiber link, in which the resulting cryptographic keys were used for one-time pad encryption of real time video signals. In this

Vortices in Attractive Bose-Einstein Condensates in Two Dimensions

July 7, 2006
Author(s)
L D. Carr, Charles W. Clark
The form and stability of quantum vortices in Bose-Einstein condensates with attractive atomic interactions is elucidated. They appear as ring bright solitons, and are a generalization of the Townes soliton to nonzero winding number m. An in?nite sequence

Quantum Key Distribution System Operating at Sifted-Key Rate over 4 Mbit/s

June 19, 2006
Author(s)
Xiao Tang, Lijun Ma, Alan Mink, Anastase Nakassis, Hai Xu, Barry J. Hershman, Joshua Bienfang, David H. Su, Ronald Boisvert, Charles W. Clark, Carl J. Williams
A complete fiber-based polarization encoding quantum key distribution (QKD) system based on the BB84 protocol has been developed at National Institute of Standard and Technology (NIST). The system can be operated at a sifted key rate of more than 4 Mbit/s

High Speed Quantum Key Distribution System Supports One-Time Pad Encryption of Real-Time Video

April 21, 2006
Author(s)
Alan Mink, Xiao Tang, Lijun Ma, Anastase Nakassis, Barry J. Hershman, Joshua C. Bienfang, David H. Su, Ronald F. Boisvert, Charles W. Clark, Carl J. Williams
NIST has developed a high-speed quantum key distribution (QKD) test bed incorporating both free-space and fiber systems. These systems demonstrate a major increase in the attainable rate of QKD systems: over two orders of magnitude faster than other

High Speed Quantum Key Distribution System Supports One-Time Pad Encryption of Real-Time Video

April 1, 2006
Author(s)
Alan Mink, Xiao Tang, Lijun Ma, Anastase Nakassis, Barry J. Hershman, Joshua Bienfang, David H. Su, Ronald Boisvert, Charles W. Clark, Carl J. Williams
NIST has developed a high-speed quantum key distribution (QKD) test bed incorporating both free-space and fiber systems. These systems demonstrate a major increase in the attainable rate of QKD systems: over two orders of magnitude faster than other

On the Absorption Spectrum of Noble Gases at the Arc Spectrum Limit

February 1, 2006
Author(s)
Ugo Fano, G Pupillo, A Zannoni, Charles W. Clark
Rydberg spectral lines of an atom are sometimes superimposed on the continuous spectrum of a different configuration. Effects of interaction among different configurations in one of these cases are theoretically investigated, and a formula is obtained that