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Physics

Quantum information science

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Displaying 851 - 875 of 934

Practical long-distance quantum key distribution system using decoy levels

April 30, 2009
Author(s)
Danna Rosenberg, Charles G. Peterson, Jim A. Harrington, Patrick R. Rice, N. Dallman, K. T. Tyagi, K. P. McCabe, Sae Woo Nam, Burm Baek, Robert Hadfield, Richard J. Hughes, Jane E. Nordholt
Quantum key distribution (QKD) has the potential for widespread real-world applications, but no secure long-distance experiment has demonstrated the truly practical operation needed to move QKD from the laboratory to the real world due largely to

Programmable Instrumentation & GHz Signaling for Quantum Communication Systems

April 30, 2009
Author(s)
Alan Mink, Joshua C. Bienfang, Robert J. Carpenter, Lijun Ma, Barry J. Hershman, Alessandro Restelli, Xiao Tang
We discussed custom instrumentation for high-speed single photon metrology. We focus on the difficulty of GHz data sampling and provide some techniques on how to accomplish it. We also discuss the benefits of field programmable gate arrays as the basis for

Electromagnetically induced transparency in a superconducting three-level system

April 16, 2009
Author(s)
Mika Sillanpaa, Katarina Cicak, Fabio Altomare, Jae Park, Raymond Simmonds, Jian Li, G. S. Paraoanu, Pertti Hakonen
When a three-level quantum system is irradiated by an intense coupling field resonant with two of the three possible transitions, the resonant absorption of the system from its ground state by an additional radiation field is suppressed. This effect, where

Improved implementation of the Alicki Van Ryn nonclassicality test for a single particle using Si detectors

April 15, 2009
Author(s)
Sergey V. Polyakov, Alan L. Migdall, Giorgio Brida, Ivo P. Degiovanni, Marco Genovese, Fabrizio Piacentini, V Schettini, Nicolas Gisin
Recently a test of nonclassicality for a single qubit was proposed R. Alicki and N. Van Ryn, J. Phys, A: Math. Theor. 41, 062001 2008. We present an optimized experimental realization of this test leading to a 46standard deviation violation of classicality

Quantum Resistant Public Key Cryptography: A Survey

April 14, 2009
Author(s)
Ray A. Perlner, David A. Cooper
Public key cryptography is widely used to secure transactions over the Internet. However, advances in quantum computers threaten to undermine the security assumptions upon which currently used public key cryptographic algorithms are based. In this paper

Restrictions on Transversal Encoded Quantum Gate Sets

March 18, 2009
Author(s)
Bryan K. Eastin, Emanuel H. Knill
Transversal gates play an important role in the theory of fault-tolerant quantum computation due to their simplicity and robustness to noise. By definition, transversal operators do not couple physical subsystems within the same code block. Consequently

Generating correlated (2+1)-photon pairs in an active-Raman-gain medium

March 5, 2009
Author(s)
Lu Deng, Cuiping Lu, Weiping Zhang, Chunhua Yuan
A scheme of generating controllable 2+1 photons in a double- atomic system based on active Raman gain is presented in this paper. Such 2+1 photons can be a potential candidate to generate a correlated photon pair as one photon of “2” photons acts as a

Tunable Delay of Einstein-Podolsky-Rosen Entanglement

February 18, 2009
Author(s)
Alberto M. Marino, Raphael C. Pooser, Vincent Boyer, Paul D. Lett
Entanglement is an important quantum resource which displays correlations between two subsystems that are stronger than the ones that can be obtained classically. This makes it the basis for a number of applications, such as quantum information processing

Optimization of photon pair generation in dual-element PPKTP waveguide1

January 5, 2009
Author(s)
Xiao Tang, Oliver T. Slattery, Lijun Ma
A compact scheme for high-speed frequency doubling and down-conversion on a single dual-element PPKTP waveguide is investigated. Optimal temperature is achieved and photon pair coincidence is observed at over GHz repetition rate with pulsed pump input

Building Quantum Computers

December 1, 2008
Author(s)
Emanuel H. Knill
In theory, quantum computers can be used to efficiently factor numbers, quadratically speed up many search and optimization problems, and enable currently impossible physics simulations. At first, quantum states appeared to be too fragile for implementing

Measuring intensity correlations with a two-element superconducting nanowire single-photon detector

November 24, 2008
Author(s)
Eric Dauler, Martin Stevens, Burm Baek, Richard J. Molnar, Scott A. Hamilton, Richard Mirin, Sae Woo Nam, Karl Berggren
Second-order intensity correlation measurements were made using a two-element superconducting nanowire single photon detector (SNSPD) without the need for an optical beam splitter. This approach can be used to obtain a 50-ps full width at half maximum

Josephson phase qubit circuit for the evaluation of advanced tunnel barrier materials

November 21, 2008
Author(s)
Jeffrey S. Kline, Haohua Wang, Seongshik Oh, John M. Martinis, David P. Pappas
We have found that crystalline Josephson junctions have critical current density control problems which decrease circuit yield. We present a qubit circuit designed to accommodate a factor-of-five variation in critical current density for the evaluation of

Long-distance entanglement-based quantum key distribution over optical fiber

November 10, 2008
Author(s)
Toshimori Honjo, Sae Woo Nam, Hiroki Takesue, Qiang Zhang, H. Kamada, Y. Nishida, O. Tadanaga, M. Asobe, Burm Baek, Robert Hadfield, Shigehito Miki, Mikio Fujiwara, Masahide Sasaki, Z. Wang, K. Inoue, Yoshihisa Yamamoto
We report the first entanglement-based quantum key distribution (QKD) experiment over a 100-km optical fiber. We used superconducting single photon detectors based on NbN nanowires that provide high-speed single photon detection for the 1.5-υm telecom band

Diagnosis of Pulsed Squeezing in Multiple Temporal Modes

August 26, 2008
Author(s)
Scott C. Glancy, Emanuel H. Knill, Thomas Gerrits, Tracy S. Clement, Martin J. Stevens, Sae Woo Nam, Richard P. Mirin
When one makes squeezed light by downconversion of a pulsed pump laser, many temporal / spectral modes are simultaneously squeezed by different amounts. There is no guarantee that any of these modes matches the pump or the local oscillator used to measure

Hanbury Brown-Twiss interferometry without a beamsplitter

August 19, 2008
Author(s)
Martin J. Stevens, Eric Dauler, Burm Baek, Richard J. Molnar, Scott A. Hamilton, Karl Berggren, Richard P. Mirin, Sae Woo Nam
We demonstrate Hanbury-Brown Twiss interferometry without a beamsplitter, by employing a single-mode optical fiber coupled to a multi-element superconducting nanowire single-photon detector.

Improved multiplexed Infrared Single Photon Detectors

August 11, 2008
Author(s)
Sergey V. Polyakov, Alan L. Migdall, V Schettini, Ivo P. Degiovanni, Giorgio Brida, F Piacentini
We discuss a scheme for a photon-counting detection system that overcomes the difficulties of photon-counting at high rates at telecom wavelengths. Our method uses an array of N detectors and a 1-by-N optical switch with a control circuit to direct input

Spectrally Bright and Broad Fiber-Based Heralded Single-Photon Source

July 29, 2008
Author(s)
Elizabeth A. Goldschmidt, M D. Eisaman, Jingyun Fan, Sergey V. Polyakov, Alan L. Migdall
We present the first experimental characterization of a heralded single-photon source based on spontaneous four-wave-mixing in a single-mode microstructure fiber. We measure the second-order correlation function, g(2)(0), to be far below the classical
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