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Search Publications by: Emanuel Knill (Fed)

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Displaying 101 - 125 of 182

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