U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Search Publications by: Emanuel Knill (Fed)

Search Title, Abstract, Conference, Citation, Keyword or Author
Displaying 51 - 75 of 93

Eigenpath Traversal by Phase Randomization

September 1, 2009
Author(s)
S. Boixo, Emanuel Knill, Rolando Somma
A computation in adiabatic quantum computing is achieved by traversing a path of nondegenerate eigenstates of a continuous family of Hamiltonians. We introduce a method that traverses a discretized form of the path: at each step we evolve with the

Generation of optical Schrodinger cat states by number-resolved squeezed photon subtraction

May 31, 2009
Author(s)
Thomas Gerrits, Scott C. Glancy, Tracy S. Clement, Brice R. Calkins, Adriana E. Lita, Aaron J. Miller, Alan L. Migdall, Sae Woo Nam, Richard P. Mirin, Emanuel H. Knill
We have generated and measured an approximation of an optical Schrödinger cat state by photon subtraction from a squeezed state. Using single-photon avalanche photodiode detectors and photon-number-resolving transition edge sensors, we were able to extract

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

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

Quantum Teleportation with Atomic Qubits

October 16, 2008
Author(s)
J Chiaverini, T Schaetz, Joseph W. Britton, Wayne M. Itano, John D. Jost, Emanuel Knill, C. Langer, Dietrich Leibfried, R Ozeri, David J. Wineland

Quantum Simulations of Classical Annealing Processes

September 26, 2008
Author(s)
Rolando Somma, S. Boixo, Howard Barnum, Emanuel Knill
We describe a quantum algorithm that solves combinatorial optimization problems by quantum simulation of a classical simulated annealing process. Our algorithm exploits quantum walks and the quantum Zeno effect induced by evolution randomization. It

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

Homodyne detection of optical cat states generated by squeezed light photon subtraction

August 19, 2008
Author(s)
Thomas Gerrits, Tracy S. Clement, Scott C. Glancy, Sae Woo Nam, Richard P. Mirin, Emanuel H. Knill
We have experimentally created and measured an optical Schrödinger Cat State. The method relies on single photon subtraction off a squeezed vacuum state and conditioning a homodyne measurement on the detection of that photon.

Liquid State NMR as a Test-bed for Developing Quantum Control Methods

July 15, 2008
Author(s)
C. A. Ryan, C. Negrevergne, M. Laforest, Emanuel Knill, R. Laflamme
Quantum mechanics has been successfully describing experimental phenomena for close to a century. However, it has only been much more recently that the idea of using quantum mechanical evolution to process information was realized. This has revolutionized

Fluorescence during Doppler cooling of a single trapped atom

November 26, 2007
Author(s)
Janus Wesenberg, Dietrich G. Leibfried, Brad R. Blakestad, Joseph W. Britton, Ryan Epstein, Jonathan Home, Wayne M. Itano, John D. Jost, Emanuel H. Knill, C. Langer, R. Ozeri, Signe Seidelin, David J. Wineland
We investigate the temporal dynamics of Doppler cooling of a single trapped atom in the weak binding regime using a semi-classical model. We develop an analytical model for the simplest case of a single vibrational mode for a harmonic trap, and show how

Transport quantum logic gates for trapped ions

September 21, 2007
Author(s)
Dietrich G. Leibfried, Emanuel H. Knill, Christian Ospelkaus, David J. Wineland
Many efforts are currently underway to build a device capable of large scale quantum information processing (QIP). While QIP has been demonstrated for a few qubits in several systems, severe difficulties have to be overcome in order to construct a large

Simplified motional heating rate measurements of trapped ions

September 19, 2007
Author(s)
Ryan Epstein, Signe Seidelin, Dietrich G. Leibfried, Janus Wesenberg, John J. Bollinger, Jason Amini, Brad R. Blakestad, Joseph W. Britton, Jonathan Home, Wayne M. Itano, John D. Jost, Emanuel H. Knill, C. Langer, R. Ozeri, Nobuyasu Shiga, David J. Wineland
We measure motional heating rates of trapped atomic ions, a factor that influences multi-ion quantum logic gate fidelities. Two simplified techniques are developed for this purpose: one relies on Raman sideband detection implemented with a single laser

Towards scaling up trapped ion quantum information processing

June 19, 2007
Author(s)
Dietrich G. Leibfried, David J. Wineland, Brad R. Blakestad, John J. Bollinger, Joseph W. Britton, J Chiaverini, Ryan Epstein, Wayne M. Itano, John D. Jost, Emanuel H. Knill, C. Langer, R Ozeri, Rainer Reichle, Signe Seidelin, Nobuyasu Shiga, Janus Wesenberg
Recent theoretical advances have identifed several computational algorithms that can be implemented utilizing quantum information processing (QIP), which gives an exponential speedup over the corresponding (known) algorithms on conventional computers. QIP

Quantum Computing with Very Noisy Devices

February 13, 2007
Author(s)
Emanuel H. Knill
This lecture was presented at the Workshop on Trapped Ion Quantum Computing hosted by NIST, February 21 - 24, 2006. It discussed the basic principles of fault-tolerant architectures for quantum computing, why we should be concerned with the resources used

Optimal Quantum Measurements of Expectation Values of Observables

January 24, 2007
Author(s)
Emanuel Knill, Gerardo Ortiz, Rolando Somma
Experimental characterizations of a quantum system involve the measurement of expectation values of observables for a preparable state |f> of the quantum system. Such expectation values can be measured by repeatedly preparing |f> and coupling the system to

Randomized Benchmarking of Quantum Gates

January 1, 2007
Author(s)
Emanuel Knill, D. Leibfried, R. Reichle, J. Britton, R. B. Blakestad, J. D. Jost, C. Langer, R Ozeri, Signe Seidelin, David J. Wineland
A key requirement for scalable quantum computing is that elementary quantum gates can be implemented with sufficiently low error. One method for determining the error behavior of a gate implementation is to perform process tomography. However, standard

Experimental purification of two-atom entanglement

October 19, 2006
Author(s)
Rainer Reichle, Dietrich G. Leibfried, Emanuel H. Knill, Joseph W. Britton, Brad R. Blakestad, John D. Jost, C. Langer, R Ozeri, Signe Seidelin, David J. Wineland
Entanglement is one of the most counterintuitive features of quantum mechanics. It is a necessary resource for quantum communication and quantum information processing. Entanglement established between different locations enables private communication and

Transport dynamics of single ions in segmented microstructured Paul trap arrays

August 4, 2006
Author(s)
Rainer Reichle, Dietrich G. Leibfried, Brad R. Blakestad, Joseph W. Britton, John D. Jost, Emanuel H. Knill, C. Langer, R Ozeri, Signe Seidelin, David J. Wineland
It was recently proposed to use small groups of trapped ions as qubit carriers in miniaturized electrode arrays that comprise a large number of individual trapping zones, between which ions could be moved. This approach might be scalable for quantum

Generalized Entanglement and Quantum Phase Transitions

July 30, 2006
Author(s)
Rolando Somma, Howard Barnum, Emanuel Knill, Gerardo Ortiz, Lorenza Viola
Effective visualizations can help researchers obtain a more complete understanding of high-level mathematical functions that arise in mathematics, statistics, physics, fluid dynamics and other fields of the mathematical and physical sciences. Accordingly

Trapped atomic ions and quantum information processing

July 16, 2006
Author(s)
David J. Wineland, Dietrich G. Leibfried, James C. Bergquist, Brad R. Blakestad, John J. Bollinger, Joseph W. Britton, J Chiaverini, Ryan Epstein, David Hume, Wayne M. Itano, John D. Jost, Emanuel H. Knill, Jeroen Koelemeij, C. Langer, R Ozeri, Rainer Reichle, Till P. Rosenband, Tobias Schaetz, Piet Schmidt, Signe Seidelin, Nobuyasu Shiga, Janus Wesenberg
The basic requirements for quantum computing and quantum simulation (Single- and multi-qubit gates, long memor times, etc.)have been demonstrated in separate experiments on trapped ions. Construction of a large-scale information processor will require

Recent experiments in trapped-ion quantum information processing at NIST

May 1, 2006
Author(s)
J Chiaverini, Matthew P. Barrett, Brad R. Blakestad, Joseph W. Britton, Wayne M. Itano, John D. Jost, Emanuel H. Knill, C. Langer, Dietrich G. Leibfried, R Ozeri, T Schaetz, David J. Wineland
Atomic ions confined in segmented trap arrays provide a system for quantum information processing. We report on the execution of two simple quantum algorithms, quantum error correction and the quantum Fourier transform, using this implementation. The

Recent experiments in trapped-ion quantum information processing at NIST

May 1, 2006
Author(s)
J Chiaverini, Murray D. Barrett, Brad R. Blakestad, Joseph W. Britton, Wayne M. Itano, John D. Jost, Emanuel H. Knill, C. Langer, Dietrich G. Leibfried, R Ozeri, Tobias Schaetz, David J. Wineland
Atomic ions confined in segmented trap arrays provide a system for quantum information processing. We report on the execution of two simple quantum algorithms, quantum error correction and the quantum Fourier transform, using this implementation. The

Error Analysis For Encoding a Qubit In An Oscillator

January 19, 2006
Author(s)
Scott Glancy, Emanuel Knill
In [5], Gottesman, Kitaev, and Preskill described a method to encode a qubit in the continuous Hilbert space of an oscillator's position and momentum variables. This encoding provides a natural error correction scheme which can correct errors due to small

Entanglement Purification of Any Stabilizer State

January 1, 2006
Author(s)
Scott Glancy, Emanuel Knill, Hilma M. Vasconcelos
We present a method for multipartite entanglement purification of any stabilizer state shared by several parties. In our protocol each party measures the stabilizer operators of a quantum error correcting code on his or her qubits. The parties exchange