quantum control

Molecular Frame Photoelectron Angular Distributions in Polyatomic Molecules from Lab Frame Coherent Rotational Wavepacket Evolution

Molecular Frame Photoelectron Angular Distributions in Polyatomic Molecules from Lab Frame Coherent Rotational Wavepacket Evolution

By Paul

Margaret Gregory, Paul Hockett, Albert Stolow, Varun Makhija

arXiv:2012.04561, Dec. 2020

The application of a matrix-based reconstruction protocol for obtaining Molecular Frame (MF) photoelectron angular distributions (MFPADs) from laboratory frame (LF) measurements (LFPADs) is explored. Similarly to other recent works on the topic of MF reconstruction, this protocol makes use of time-resolved LF measurements, in which a rotational wavepacket is prepared and probed via photoionization, followed by a numerical reconstruction routine; however, in contrast to other methodologies, the protocol developed herein does not require determination of photoionization matrix elements, and consequently takes a relatively simple numerical form (matrix transform making use of the Moore-Penrose inverse). Significantly, the simplicity allows application of the method to the successful reconstruction of MFPADs for polyatomic molecules. The scheme is demonstrated numerically for two realistic cases, N2 and C2H4. The new technique is expected to be generally applicable for a range of MF reconstruction problems involving photoionization of polyatomic molecules.


 

Angle-resolved RABBIT: theory and numerics

Angle-resolved RABBIT: theory and numerics

By Paul

Update 28/06/17 – Now published in J. Phys. B, special issue on Correlations in Light-Matter Interactions.

New manuscript:

Angle-resolved RABBIT: theory and numerics

P. Hockett

Angle-resolved (AR) RABBIT measurements offer a high information content measurement scheme, due to the presence of multiple, interfering, ionization channels combined with a phase-sensitive observable in the form of angle and time-resolved photoelectron interferograms. In order to explore the characteristics and potentials of AR-RABBIT, a perturbative 2-photon model is developed; based on this model, example AR-RABBIT results are computed for model and real systems, for a range of RABBIT schemes. These results indicate some of the phenomena to be expected in AR-RABBIT measurements, and suggest various applications of the technique in photoionization metrology.

Paul Hockett 2017 J. Phys. B: At. Mol. Opt. Phys. 50 154002

Pre-print available via Authorea, DOI: 10.22541/au.149037518.89916908.

arXiv 1703.08586 (2017) 

See also the recent AR-RABBIT presentation for a brief intro to this topic.

Angle-resolved RABBIT: new work and presentation

Angle-resolved RABBIT: new work and presentation

By Paul

The above image shows simulated velocity map images (left, middle) and angle and time-resolved measurements (right) for angle-resolved RABBIT measurements. In this type of measurement, XUV and IR pulses are combined, and create a set of 1 and 2-photon bands in the photoelectron spectrum. The presence of multiple interfering pathways to each final photoelectron band (energy) results in complex and information rich interferograms, with both angle and time-dependence.

A manuscript detailing this work is currently in preparation, and a recent presentation detailing some aspects of the work can be found on Figshare.

Update 24th March – new manuscript, Angle-resolved RABBIT: theory and numerics, pre-print available.

Coherent quantum control & metrology

Coherent quantum control & metrology

By Paul

UPDATE March 2016 – The article has been chosen for the JPB Highlights of 2015 selection, which features articles selected for their “outstanding quality and impact within the field”. The articles in the collection will be open access for the year.

Our recent paper on coherent control & quantum metrology is now published in J. Phys. B:

Coherent control of photoelectron wavepacket angular interferograms
P Hockett, M Wollenhaupt and T Baumert
J. Phys. B: At. Mol. Opt. Phys. 48 (2015) 214004.
doi: 10.1088/0953-4075/48/21/214004

Coherent control over photoelectron wavepackets, via the use of polarization-shaped laser pulses, can be understood as a time and polarization-multiplexed process, where the final (time-integrated) observable coherently samples all instantaneous states of the light–matter interaction. In this work, we investigate this multiplexing via computation of the observable photoelectron angular interferograms resulting from multi-photon atomic ionization with polarization-shaped laser pulses. We consider the polarization sensitivity of both the instantaneous and cumulative continuum wavefunction; the nature of the coherent control over the resultant photoelectron interferogram is thus explored in detail. Based on this understanding, the use of coherent control with polarization-shaped pulses as a methodology for a highly multiplexed coherent quantum metrology is also investigated, and defined in terms of the information content of the observable.

The work is part of the special issue on Coherence and Control in the Quantum World.

The manuscript is also available on the arxiv.

UPDATE Nov. 2015 – Chosen for the cover of the 14th November 2015 print edition.

JPB cover

Maximum-information photoelectron metrology

Maximum-information photoelectron metrology

By Paul

Two new articles, on quantum metrology via polarization-shaped pulses (mostly theory) and maximum-information photoelectron metrology via tomographic measurements (mostly experiment), have just been published in PRA.

Complete photoionization experiments via ultrafast coherent control with polarization multiplexing. II. Numerics and analysis methodologies

P. Hockett, M. Wollenhaupt, C. Lux, and T. Baumert

Phys. Rev. A 92, 013411 – Published 13 July 2015

(also available at arXiv:1503.08247 (2015))

 

Maximum-information photoelectron metrology

P. Hockett, C. Lux, M. Wollenhaupt, and T. Baumert

Phys. Rev. A 92, 013412 – Published 13 July 2015

(also available at arXiv:1503.08308 (2015))

Ultrafast atomic and molecular physics with cutting-edge light sources: New opportunities and challenges

Ultrafast atomic and molecular physics with cutting-edge light sources: New opportunities and challenges

By Paul

Originally presented at ITAMP’s (Institute for Theoretical, Atomic and Molecular and Optical Physics, part of the Harvard-Smithsonian Center for Astrophysics) workshop on Ultrafast atomic and molecular physics with cutting-edge light sources: New opportunities and challenges, back in Nov. 2013.

Thanks to ITAMP for the video!

 

Information content of polarization-shaped pulses

Information content of polarization-shaped pulses

By Paul

Playing around with visualization of the information content of polarization-shaped pulses, which represent a way to coherently sample (over the pulse duration) a range of points in polarization space.  Here’s a plot showing the coherent paths followed for a range of different pulses, generated by putting a step function on the spectral phase of a broadband (~60fs) pulse, with the instantaneous pulse polarization expressed as Stokes vectors and projected onto a Poincare Sphere.

Update 4th May – the manuscript (a version of) this figure appears in is now on the arxiv.