Reading today…

Reading today…

Nonlinear quantum optics mediated by Rydberg interactions

O Firstenberg, C S Adams and S Hofferberth

Published 30 June 2016© 2016 IOP Publishing Ltd
Journal of Physics B: Atomic, Molecular and Optical Physics, Volume 49, Number 15
Special Issue on Rydberg Atomic Physics

By mapping the strong interaction between Rydberg excitations in ultra-cold atomic ensembles onto single photons via electromagnetically induced transparency, it is now possible to realize a medium which exhibits a strong optical nonlinearity at the level of individual photons. We review the theoretical concepts and the experimental state-of-the-art of this exciting new field, and discuss first applications in the field of all-optical quantum information processing.

DOI: 10.1088/0953-4075/49/15/152003

Fascinating insight into the topic, which utilises the properties of Rydberg matter to enable traditional non-linear optics to cross over to the quantum regime. From the intro:

One remarkable success of advances in ultra-cold Rydberg physics is the realization of a medium with a large optical nonlinearity at the single photon level [1–3]. Highly excited Rydberg atoms bring something new to the history of optics as they enable quantum nonlinear media where photons are strongly interacting!


Angle-resolved RABBIT: theory and numerics

Angle-resolved RABBIT: theory and numerics

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.

Open Science Initiative

Open Science Initiative

Open science – the practice of making full research projects open and accessible, from inception to publication – is an increasingly important topic, and even appearing in the popular press, particularly with regard to transparency and reproducible in research… hence open science can be viewed as the opposite of bad science.

John Arnold Made a Fortune at Enron. Now He’s Declared War on Bad Science

Open science (along with the more general notion of open data) is also part of the Canadian Government’s Open Government action plan, which includes the statement that:

The Government of Canada will maximize access to federally-funded scientific research to encourage greater collaboration and engagement with the scientific community, the private sector, and the public.


As part of our work towards open science, our articles are increasingly available on open platforms (arXiv, Authorea). And, now, good things are happening with our data too. Thanks to the Open Science Foundation (OSF) and Figshare, it’s now easy to share data, code etc. and make it citable with a DOI.

Some of our recent open science data can be found at:

Time-dependent Wavepackets and Photoionization – CS2 (2013 – present)

Our ongoing work on the calculation of time-dependent wavepackets and observables in photoionization is now collected in an OSF project (DOI: 10.17605/OSF.IO/RJMPD). Aspects of this work have previously been published, but much of the detail and methodology underlying the calculations has remained sitting on our computers. As part of our Open Science Initiative, we’re letting this data go free! Head over to the OSF project “Time-dependent Wavepackets and Photoionization – CS2” for more.

Time-resolved multi-mass ion imaging: femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera (2017)

Bootstrapping to the Molecular Frame with Time-domain Photoionization Interferometry (2017)

Time Delay in Molecular Photoionization (2016)

Let your data be free!

Angle-resolved RABBIT: new work and presentation

Angle-resolved RABBIT: new work and presentation

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.

Monitoring Non-adiabatic Dynamics in CS2 with Time- and Energy-Resolved Photoelectron Spectra of Wavepackets

Monitoring Non-adiabatic Dynamics in CS2 with Time- and Energy-Resolved Photoelectron Spectra of Wavepackets

Feb. 2017 – New article in Chemical Physics Letters:

Monitoring Non-adiabatic Dynamics in CS2 with Time- and Energy-Resolved Photoelectron Spectra of Wavepackets

Kwanghsi Wang(a) Vincent McKoy(a)Paul Hockett(b)Albert Stolow(b, c, d),Michael S. Schuurman(b, d),

a A. A. Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, California 91125, USA

b National Research Council Canada, 100 Sussex Drive, Ottawa, Ontario K1A 0R6, Canada

c Department of Physics, University of Ottawa, ON K1N 6N5 Canada

d Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, ON, K1N 6N5, Canada


• Time-resolved photoelectron angular distributions around conical intersections are studied.
• Ab initio multiple spawning method is applied to obtain wavepacket densities.
• Geometry and energy dependent photoelectron matrix elements are employed.
• Molecular and laboratory photoelectron angular distributions are used to illustrate the non-adiabatic dynamics.
• Photoelectron spectra are compared with measured values.


We report results from a novel fully ab initio method for simulating the time-resolved photoelectron angular distributions around conical intersections in CS2. The technique employs wavepacket densities obtained with the multiple spawning method in conjunction with geometry- and energy-dependent photoionization matrix elements. The robust agreement of the calculated molecular-frame photoelectron angular distributions with measured values for CS2 demonstrates that this approach can successfully illuminate, and disentangle, the underlying coupled nuclear and electronic dynamics around conical intersections in polyatomic molecules.

DOI: 10.1016/j.cplett.2017.02.014

Time-resolved multi-mass ion imaging: femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera

Time-resolved multi-mass ion imaging: femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera

UPDATE: Dec. 2017

The figure above has made it as the JCP Christmas card!

The  full JCP special issue on Velocity Map Imaging Techniques is also now officially ready, see this page, or this PDF, for all the details.

UPDATE: 4th April 2017

The article is now published in the Journal of Chemical Physics, with an accompanying press release, The Inner Lives of Molecules, from AIP.

The full dataset and analysis scripts are now also available via OSF, DOI: 10.17605/OSF.IO/RRFK3.

Feb. 2017 – new article on the arXiv:

Time-resolved multi-mass ion imaging: femtosecond UV-VUV pump-probe spectroscopy with the PImMS camera

The Pixel-Imaging Mass Spectrometry (PImMS) camera allows for 3D charged particle imaging measurements, in which the particle time-of-flight is recorded along with (x,y) position. Coupling the PImMS camera to an ultrafast pump-probe velocity-map imaging spectroscopy apparatus therefore provides a route to time-resolved multi-mass ion imaging, with both high count rates and large dynamic range, thus allowing for rapid measurements of complex photofragmentation dynamics. Furthermore, the use of vacuum ultraviolet wavelengths for the probe pulse allows for an enhanced observation window for the study of excited state molecular dynamics in small polyatomic molecules having relatively high ionization potentials. Herein, preliminary time-resolved multi-mass imaging results from C2F3I photolysis are presented. The experiments utilized femtosecond UV and VUV (160.8~nm and 267~nm) pump and probe laser pulses in order to demonstrate and explore this new time-resolved experimental ion imaging configuration. The data indicates the depth and power of this measurement modality, with a range of photofragments readily observed, and many indications of complex underlying wavepacket dynamics on the excited state(s) prepared.

arXiv 1702.00744 (2017)

Now published in JCP:
The Journal of Chemical Physics 147, 013911 (2017);

Also on Authorea, DOI: 10.22541/au.149030711.19068540



Reading today…

Reading today…

First On-Sky Fringes with an Up-Conversion Interferometer Tested on a Telescope Array

P. Darré, R. Baudoin, J.-T. Gomes, N. J. Scott, L. Delage, L. Grossard, J. Sturmann, C. Farrington, F. Reynaud, and T. A. Ten Brummelaar
Phys. Rev. Lett. 117, 233902 – Published 29 November 2016


The Astronomical Light Optical Hybrid Analysis project investigates the combined use of a telescope array interferometer and nonlinear optics to propose a new generation of instruments dedicated to high-resolution imaging for infrared astronomy. The nonlinear process of optical frequency conversion transfers the astronomical light to a shorter wavelength domain. Here, we report on the first fringes obtained on the sky with the prototype operated at 1.55μm in the astronomical H band and implemented on the Center for High Angular Resolution Astronomy telescope array. This seminal result allows us to foresee a future extension to the challenging midinfrared spectral domain.

This is quite interesting as an application of photon up-conversion at low-light levels – in this case for interferometric IR telescope arrays.  The demo in the paper doesn’t show any improvement on the existing configuration (i.e. no non-linear optical step), but in principle could: once one factors in not just lossy detection in the IR, but also lossy beam transport (in the conceptually similar VLTI system it’s about 10% efficient).

The header image shows fig. 1 from the paper.

ePSproc: Post-processing suite for ePolyScat electron-molecule scattering calculations

ePSproc: Post-processing suite for ePolyScat electron-molecule scattering calculations

New on the arxiv:

ePSproc: Post-processing suite for ePolyScat electron-molecule scattering calculations

P. Hockett

ePSproc provides codes for post-processing results from ePolyScat (ePS), a suite of codes for the calculation of quantum scattering problems, developed and released by Luchesse & co-workers (Gianturco et al. 1994)(Natalense and Lucchese 1999)(R. R. Lucchese and Gianturco 2016). ePS is a powerful computational engine for solving scattering problems, but its inherent complexity, combined with additional post-processing requirements, ranging from simple visualizations to more complex processing involving further calculations based on ePS outputs, present a significant barrier to use for most researchers. ePSproc aims to lower this barrier by providing a range of functions for reading, processing and plotting outputs from ePS. Since ePS calculations are currently finding multiple applications in AMO physics (see below), ePSproc is expected to have significant reuse potential in the community, both as a basic tool-set for researchers beginning to use ePS, and as a more advanced post-processing suite for those already using ePS. ePSproc is currently written for Matlab/Octave, and distributed via Github: