Professor Ian A. Walmsley
Professor of Experimental Physics
Ultrafast quantum optics
Optics has played, and continues to play, a central role in physics. Not only does it provides an underpinning technology that enables scientific research in areas as diverse as biology and atomic frequency standards, but also, because it comfortably straddles the boundary between the quantum and classical worlds, it has provided important insights into the nature of quantum mechanics itself.
The aim of our research is to manipulate atoms and molecules using classical light, and to generate and study the properties of non-classical light from atoms and molecules, using state of the art laser systems and ancillary technologies. The interaction of light and matter at this fundamental level has broad application both in physics and in future technologies.
To achieve this aim, the Ultrafast Group sustains research efforts in three areas: quantum optics, coherent control of atoms and molecules and nonlinear optics. These areas are connected by the common theme of manipulation and characterization of the wave fields, both radiation and matter, that are the underlying entities of the apposite physical theories.
Current projects include: the development of high-fidelity single and few photons sources for quantum information science; the synthesis of ultracold molecules from trapped ultracold atoms using closed-loop control and the development of methods for complete characterization of attosecond-duration electromagnetic pulses for novel time-resolved spectroscopies.
"Conditional preparation of single photons for scalable quantum-optical networking". A. U'Ren, Ch. Silberhorn, K. Banaszek and I. A. Walmsley,Phys. Rev. Lett., 93, 093601 (2004).
How to make just one photon, to know when you have, and to put it where you want it.
"Fiber-assisted photon-number resolving detector". D. Achilles, Ch. Silberhorn, C. Sliwa, K. Banaszek and I. A. Walmsley. Opt. Lett., 28, 2387 (2003)
How to count many photons using Yes/No detectors. (No, No, Yes, Yes, No, No, No....)
"Managing photons for quantum information processing". A. U'Ren, E. Mukamel, K. Banaszek and I. A. Walmsley. (invited paper) Phil. Trans. (Roy. Soc.), 361, 1493 (2003).
How to make photons conform to a strict shape-up regimen, so they can run interference for one another.
"Joint quantum state measurement using unbalanced array detection". M. Beck, C. Dorrer and I. A. Walmsley.
Phys. Rev. Lett., 85, 253601 (2001)
A novel way of making joint quantum state measurements on pulsed light beams without the usual mode matching problems.
"Violation of Bell-inequality violation by a generalized EPR state using homodyne detection". A. Kuzmich, I. A. Walmsley and L. Mandel. Phys. Rev. Lett., 85, 1349 (2000)
What you measure is an integral part of local realism - here even
Gaussian states can exhibit nonlocal behavior using weak field
"Decoherence of molecular vibrational wave packets: Observable manifestations and control criteria", C. Brif, H. Rabitz, S. Wallentowitz and I. A. Walmsley. Phys. Rev. A, 63, 063404 (2001). Is coherent control of decoherence a sensible idea?
"Analytic Solution for Strong-Field Quantum Control of Atomic Wave Packets", L. De Araujo, I. A. Walmsley and C. R. Stroud, Jr. Phys. Rev. Lett., 81, 955 (1998).
A solution to the problem of getting just what you want, when you want it, and in the quantities you want it. At least for atomic electrons
"Experimental Determination of the Quantum-Mechanical State of a Molecular Vibrational Mode Using Fluorescence Tomography". T. Dunn, I. A. Walmsley and S. Mukamel. Phys. Rev. Lett., 74, 884 (1995).
Just to make sure you've gotten what you want, you need a quantum
"Direct space-time characterization of the electric-field of ultrashort optical pulses". C. Dorrer, E.M. Kosik and I.A. Walmsley. Opt. Lett., 27, 548 (2002).
Measuring the complete spatio-temporal field of a femtosecond pulse shows the difficulty in handling really large bandwidth light.
"Precision and consistency criteria in Spectral Phase Interferometry for Direct Electric-field Reconstruction". C. Dorrer and I. A. Walmsley. Jnl. Opt. Soc. Am. B, 19, 1030 (2002).
How to know you've got it right with SPIDER.
"Spatially resolved amplitude and phase characterization of femtosecond optical pulses". L. Gallman, G. Steinmeyer, D. H. Sutter, T. Rupp, C. Iaconis, I. A. Walmsley and U. Keller. Opt. Lett., 26, 96 (2001).
SPIDER applied to some of the shortest optical pulses ever made, at least at the time!
"Spectral Phase Interferometry for Direct Electric Field Reconstruction of Ultrashort Optical Pulses", C. Iaconis and I. A. Walmsley. Opt. Lett., 23, 792 (1998).
The first SPIDER paper. (http://ultrafast.physics.ox.ac.uk/spider/index.html)