Academic publications
J-P Stacey's academic writing
Summary
This is a list of J-P Stacey's academic publications. The location of all documents listed here ought to be permanent: this list itself will probably be temporary pending new website construction.
Thesis
Stabilization and Control In a Linear Ion Trap
A thesis submitted for the degree of Doctor of Philosophy
Trinity Term, 2003; Wadham College, Oxford
If a book's worth is determined by its weight, either in condensed hours or in pages, then it's worth stating that my thesis was the culmination of nearly three years of research in the Clarendon Laboratory. It took some nine months to write and contains 186 pages. The last figure is of note from a purely practical point of view, for those thinking of reading it from end to end.
The value of the contents is more subjective. Whereas many theses attempt a grand narrative, with all chapters focussed on the same problem, mine has such an aim only insofar as everyone in the group was moving towards the same ultimate goal: quantum computation. As an experimental physicist attempting to lay the foundations (often brass and duraluminium, if not strictly concrete) for what will eventually be complex and subtle experiments, my perspective was often restricted to the problem at hand, itself typically a technical or engineering task.
Nonetheless, this written work is, I hope, useful to anyone working in a number of fields. Each chapter tells a story of the tackling of a different area of either theory or experiment, and there is help and advice (and often the handy mapping-out of dead ends that others would do well to avoid). My thesis touches upon, among other subjects:
- The principles, and practicability, of ion state detection
- Construction and testing of a near-infra red laser
- Laser cooling and thermal heating of a single, three-level ion
- Megahertz radiofrequency amplification using a helical resonator
- Measuring magnetic fields with a single ion, and controlling the field with coils
- Photoionization of an atomic beam to populate an ion trap
Along with these varied descriptions, there are results that are key and occasionally the first ever instance of such; although such work will not revolutionize the subject, truly they also serve who stand and work metal.
If you find it useful, please feel free to keep my thesis locally, on your own computer. The only request I make of you in return is that you contact me to let me know.
Academic Papers
The following is a selection of academic papers which I have co-authored. It was standard practice for the entire group to be credited on each paper, even though typically my work was entirely experimental or analytical. I therefore can't guarantee my strict authorship of much of the below....
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High-Efficiency Detection of a Single Quantum of Angular Momentum by Suppression of Optical Pumping
M. J. McDonnell, J.-P. Stacey, S. C.Webster, J. P. Home, A. Ramos, D.M. Lucas, D. N. Stacey, and A.M. Steane
Phys. Rev. Lett, 93(15), 153601 (2004)
Abstract
We propose and demonstrate experimentally the discrimination between two spin states of an atom purely on the basis of their angular momentum. The discrimination relies on angular momentum selection rules and does not require magnetic effects such as a magnetic dipole moment of the atom or an applied magnetic field. The central ingredient is to prevent by coherent population trapping an optical pumping process which would otherwise relax the spin state before a detectable signal could be obtained. We detected the presence or absence of a single quantum (1 ℏ) of angular momentum in a trapped calcium ion in a single observation with success probability 0.86. As a practical technique, the method can be applied to read out some types of quantum computer.
Article
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Isotope-selective photoionization for calcium ion trapping
D. M. Lucas, A. Ramos, J. P. Home, M. J. McDonnell, S. Nakayama, J.-P. Stacey, S. C. Webster, D. N. Stacey, and A. M. Steane
Phys. Rev. A, 69, #012711 (2004)
Abstract
We present studies of resonance-enhanced photoionization for isotope-selective loading of Ca+ into a Paul trap. The 4s2 1S0<-->4s4p 1P1 transition of neutral calcium is driven by a 423 nm laser and the atoms are photoionized by a second laser at 389 nm. Isotope selectivity is achieved by using crossed atomic and laser beams to reduce the Doppler width significantly below the isotope shifts in the 423 nm transition.
The loading rate of ions into the trap is studied under a range of experimental parameters for the abundant isotope 40Ca+. Using the fluorescence of the atomic beam at 423 nm as a measure of the Ca number density, we estimate a lower limit for the absolute photoionization cross section of 170(60) Mb. We achieve loading and laser cooling of all the naturally occurring isotopes, without the need for enriched sources. Laser heating/cooling is observed to enhance the isotope selectivity.
In the case of the rare species 43Ca+ and 46Ca+, which have not previously been laser cooled, the loading is not fully isotope selective, but we show that pure crystals of 43Ca+ may nevertheless be obtained. We find that for loading 40Ca+ the 389 nm laser may be replaced by an incoherent source.
Article
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Oxford ion-trap quantum computing project
D. M. Lucas, C. J. S. Donald, J. P. Home, M. J. McDonnell, A. Ramos, D. N. Stacey, J.-P. Stacey, A. M. Steane, S. C. Webster
Phil. Trans. R. Soc. Lond. A, 361, pp. 1401–1408 (2003)
Abstract
We describe recent progress in the development of an ion-trap quantum information processor. We discuss the choice of ion species and describe recent experiments on read-out for a ground-state qubit and photoionization trap loading.
Article
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Search for correlation effects in linear chains of trapped ions
Donald, C J S ; Lucas, D M ; Barton, P A ; McDonnell, M J ; Stacey, J P ; Stevens, D A ; Stacey, D N ; Steane, A M
Europhys. Lett, 51(4), pp. 388–394 (2000)
Abstract
We report a precise search for correlation effects in linear chains of 2 and 3 trapped Ca+ ions. Unexplained correlations in photon emission times within a linear chain of trapped ions have been reported, which, if genuine, cast doubt on the potential of an ion trap to realize quantum information processing. We observe quantum jumps from the metastable 3d 2D5/2 level for several hours, searching for correlations between the decay times of the different ions.
We find no evidence for correlations: the number of quantum jumps with separations of less than 10 ms is consistent with statistics to within errors of 0.05%; the lifetime of the metastable level derived from the data is consistent with that derived from independent single-ion data at the level of the experimental errors 1%; and no rank correlations between the decay times were found with sensitivity to rank correlation coefficients at the level of |R| = 0.024.
Article