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Browsing Research Publications/Outputs by Author "Uys, H"

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Analytically exploiting noise correlations inside the feedback loop to improve locked-oscillator performance

Author: Sastrawan, J ; Jones, C ; Akhalwaya, I ; Uys, H ; Biercuk, MJ Date: Aug 2016 We introduce concepts from optimal estimation to the stabilization of precision frequency standards limited by noisy local oscillators. We develop a theoretical framework casting various measures for frequency standard variance in terms of ... Read more
Arbitrary quantum control of qubits in the presence of universal noise

Author: Green, TJ ; Sastrawan, J ; Uys, H ; Biercuk, MJ Date: Sep 2013 We address the problem of deriving analytic expressions for calculating universal decoherence-induced errors in qubits undergoing arbitrary, unitary, time-dependent quantum control protocols. We show that the fidelity of a control operation ... Read more
Controlling the quantum world with light

Author: Uys, H ; Akhalwaya, I ; Botha, N ; Burd, S ; Hendriks, A ; Madigoe, R ; Ombinda-Lemboumba, Saturnin ; Smit, A ; Kloppers, H ; Steyn, J ; Botha, L Date: Oct 2012 In this presentation the authors discuss the technological relevance of quantum mechanics, and describe how researchers use light to control the atomic and molecular world at its most fundamental level. Read more
Coupled optical resonance laser locking

Author: Burd, CC ; Du Toit, PJW ; Uys, H Date: Oct 2014 We have demonstrated simultaneous laser frequency stabilization of a UV and IR laser, to coupled transitions of ions in the same spectroscopic sample, by detecting only the absorption of the UV laser. Separate signals for locking the different ... Read more
Decoherence due to elastic rayleigh scattering

Author: Uys, H ; Biercuk, MJ ; VanDevender, AP ; Ospelkaus, C ; Meiser, D ; Ozeri, R ; Bollinger, JJ Date: Nov 2010 The authors present theoretical and experimental studies of the decoherence of hyperfine ground-state superpositions due to elastic Rayleigh scattering of light off resonant with higher lying excited states. They demonstrate that under ... Read more
Decoherence of superposition states in trapped ions

Author: Uys, H ; Biercuk, M ; Van Devender, AP ; Ospelkaus, C ; Meiser, D ; Ozeri, R ; Bollinger, JJ Date: Sep 2010 This paper investigates the decoherence of superpositions of hyperfine states of 9Be+ ions due to spontaneous scattering of off-resonant light. It was found that, contrary to conventional wisdom, elastic Raleigh scattering can have major ... Read more
Detecting yocto (10-24) newton forces with trapped ions

Author: Uys, H ; Biercuk, M ; Britton, JW ; Van Devender, AP ; Bollinger, JJ Date: Sep 2010 This article reports on a calibrated measurement of 174 Yoctonewton using a cloud of 60 9 Be+ ion confined in a Penning ion trap. These measurements suggest that ion traps may form the basis of a new class of ultrasensitive deployable force sensors. Read more
Engineered two-dimensional Ising interactions in a trapped-ion quantum simulator with hundreds of spins

Author: Britton, JW ; Sawyer, BC ; Keith, AC ; Wang, CCJ ; Freericks, JK ; Uys, H ; Biercuk, MJ ; Bollinge, JJ Date: Apr 2012 The presence of long-range quantum spin correlations underlies a variety of physical phenomena in condensed-matter systems, potentially including high-temperature superconductivity. However, many properties of exotic, strongly correlated spin ... Read more
Experimental bath engineering for quantitative studies of quantum control

Author: Soare, A ; Ball, H ; Hayes, D ; Zhen, X ; Jarratt, MC ; Sastrawan, J ; Uys, H ; Biercuk, MJ Date: Apr 2014 We develop and demonstrate a technique to engineer universal unitary baths in quantum systems. Using the correspondence between unitary decoherence due to ambient environmental noise and errors in a control system for quantum bits, we show ... Read more
Femtosecond laser control of chemical reaction of carbon monoxide and hydrogen

Author: Du Plessis, A ; Strydom, CA ; Uys, H ; Botha, L ; Roberts, T ; Dlamini, TH Date: Sep 2010 Femtosecond laser control of chemical reactions is made possible through the use of pulse-shaping techniques coupled to a learning algorithm feedback loop – teaching the laser pulse to control the chemical reaction. This can result in ... Read more
Femtosecond laser control of chemical reactions

Author: Du Plessis, A ; Strydom, CA ; Uys, H ; Botha, L ; Roberts, T ; Dlamini, TH Date: 31 Aug 2010 Femtosecond laser control of chemical reactions is made possible through the use of pulse-shaping techniques coupled to a learning algorithm feedback loop – teaching the laser pulse to control the chemical reaction. This can result in ... Read more
Femtosecond laser induced and controlled chemical reaction of carbon monoxide and hydrogen

Author: Du Plessis, A ; Strydom, CA ; Uys, H ; Hendriks, A ; Botha, GN ; Botha, LR Date: Jul 2011 Results from experiments aimed at bimolecular chemical reaction control of CO and H2 at room temperature and pressure, without any catalyst, using shaped femtosecond laser pulses are presented. A stable reaction product (CO2) was measured ... Read more
High-order noise filtering in nontrivial quantum logic gates

Author: Green, T ; Uys, H ; Biercuk, MJ Date: Jul 2012 Treating the effects of a time-dependent classical dephasing environment during quantum logic operations poses a theoretical challenge, as the application of noncommuting control operations gives rise to both dephasing and depolarization ... Read more
Implementation schemes for unsharp measurements with trapped ions

Author: Choudhary, SK ; Konrad, T ; Uys, H Date: Jan 2013 Unsharp positive operator-valued measurements allow a variety of measurement applications which minimally disrupt the state of the quantum system. Experimental schemes are proposed for implementing unsharp measurements on the qubit levels of ... Read more
Laser coherent control of quantum dynamics at the CSIR: NLC

Author: Botha, L ; Du Plessis, A ; Uys, H ; de Clercq, L Date: 01 Sep 2010 Coherent control of quantum dynamics in optical, molecular and biological systems is a rapidly advancing field with many possible applications. This field of study was originally motivated by the goal of steering photoreactions into specific ... Read more
Maintaining quantum coherence in the presence of noise through state monitoring

Author: Konrad, T ; Uys, H Date: Jan 2012 Unsharp measurements allow the estimation and tracking of quantum wave functions in real time with minimal disruption of the dynamics. Here we demonstrate that high-fidelity state monitoring, and hence quantum control, is possible, even in ... Read more
Process tomography via sequential measurements on a single quantum system

Author: Bassa, H ; Goyal, SK ; Choudhary, SK ; Uys, H ; Diósi, L ; Konrad, T Date: Sep 2015 The authors utilize a discrete (sequential) measurement protocol to investigate quantum process tomography of a single two-level quantum system, with an unknown initial state, undergoing Rabi oscillations. The ignorance of the dynamical ... Read more
Prolonging coherence in trapped ions

Author: Uys, H ; Biercuk, M ; Van Devender, AP ; Bollinger, JJ Date: Sep 2010 The authors study pulse sequences that dynamically decouple 9Be+ ions from their decohering environment. The noise environment the ions see is artificially synthesized to emulate a variety of physical systems. By incorporating measurement ... Read more
Pulse shaping and characterization with a 4f system

Author: Botha, N ; Botha, L ; Du Plessis, A ; Uys, H ; Schoewer, H Date: Oct 2010 The design of the pulse shaping setup as well as factors taken into account in choosing a specific setup will be discussed. We investigate the generation of simple shaped pulses to test our pulse shaper setup. Difference frequency mixing is ... Read more
Scaling ion traps for quantum computing

Author: Uys, H ; Amini, JM ; Wesenberg, JH ; Seidelin, S ; Britton, J ; Bollinger, JJ ; Leibfried, D ; Ospelkaus, C ; Van Deventer, AP ; Wineland, DJ Date: Sep 2010 The design, fabrication and preliminary testing of a chipscale, multi-zone, surface electrode ion trap is reported. The modular design and fabrication techniques used are anticipated to advance scalability of ion trap quantum computing architectures Read more

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