Quantum Measurement and Manipulation Group

   

NEWS 

Latest news 

  • The Alice swarm challenge is on! We opened up the to remote access to the experiment through gameplay on the 27th of September. Participate in a real quantum experiment on alice.scienceathome.org.
  • The Alice team challenge is on! We opened up for remote access to the experiment through gameplay on the 19th of September. Follow on alice.scienceathome.org. We observed this beautiful BEC transition in the lab on the 16th of September. The BEC is created with the help of a so-called dimple, a very tightly focussed laser beam.
  • Jens Schultz Laustsen joins the group as a PhD on the 1st of August 2016. Jens is familiar to us, as he did his Bachelors project with us last summer. Big welcome to Jens.
  • Jacob Sherson and Aske Thorsen flew all the way to Austin, Texas to participate in the National Instruments Week at beginning of August 2016, and display the capabilities of our remote experiment interface. 
  • We said farewell to our postdoc Mario Napolitano who left on the 31st of July 2016. Thanks for fantastic 2 years, and good luck in future work!
  • Our masters student Søren Mikkelsen successfully defended his project Homodyne detection of ultracold atomic clouds on the 21th July 2016. We congratulate him, and thank for his contribution to our new homodyne imaging setup.
  • On the 11th of July we just submitted a preprint on the ArXiv of our new paper Measurement-enhanced determination of BEC phase diagrams. Find out how to utilize Faraday imaging, to enhance the performance of your ultracold atoms experiment, here: arxiv.org/abs/1607.02934.
  • Over the summer, optimal control experts; an experimentalist, and a young student have had remote access to our experiment in order to create as large BECs as possible. Stay tuned for the exciting results.
  • We observed Larmor precession of atoms in the lab on the 23rd of June. Our atoms are magnetized, and when they are abruptly exposed to a magnetic field, pointing in a different direction than their magnetization, the start rotating around this external field. This effect can be used to measure magnetic fields very precisely. 
  • We congratulate our masters student Søren Christensen on fulfillment of his masters degree, with a project entitled Step-by-step Optimization of the Production of Ultra Cold Atoms, defended on the 6th of May 2016. Thank you for your contribution to the understanding of the fundamentals of our experiment, the MOT and the evaporation process.
  • The groups’ first PhD student Romain Müller successfully defended his thesis on the 14th of January 2016. Romain has been with us since the dawn of man, and we are happy to announce that he will be staying with us for longer as a postdoc! Congratulations once again.
  • Jakob Flyger Jørgensen, our Master’s student defended his thesis Generation of arbitrary Potential Landscapes for Ultra Cold Atoms with success on the 8th of January 2016. Thank you for your valuable input to the experiment.
  • Aske Thorsen defended his project A modular control system for cold atom experiments on the 9th of October 2015. Aske’s contribution is truly invaluable. As his project he developed from scratch a new and a very flexible control system for the whole experiment entitled Alice. We are also happy to announce that Aske will be staying for longer time to continue the development of the software.
  • On the 31st of September 2015 our postdoc for 3 years, Mark Bason left the group, for a new and an exciting position in Nottingham. We thank Mark for his invaluable contribution to the experiment, it wouldn't have been the same without you.
  • We welcome Ottó Elíasson who joined the team as a PhD student on the 1st of September 2015. Ottó is no newbie in the group, and has been around since spring 2014.

Welcome to Nicolas

Nicolas Auvrey has recently joined the group from the ENS in Lyon for a three month internship. During his stay he will be working on magnetic field stabilisation and spatial light modulation. (05/15)

Congratulations to Robert

On the 15th of January Robert Heck successfully defended his progress report "Creation of 87Rb Bose-Einstein Condensates in Different Trap Configurations". The external examiner was Jörg Helge Müller from the Niels Bohr Institute. (01/2015)

Congratulations to Mads

On the 14th of January Mads Kock Pedersen successfully defended his master's thesis "Human and measurement-based quantum optimization and game-based education". The external examiner was Niels O. Andersen from the Niels Bohr Institute. (01/2015)

Many-body state engineering using measurements and fixed unitary dynamics

Published in New Journal of Physics

State preparation in high-dimensional Hilbert-spaces does not require control over a system Hamiltonian or over applicable measurement operators: We show how to prepare a desired state or subspace, given a static projection operator onto the desired target that is applied repeatedly at optimised moments in time. Benchmarks against other schemes, performed on random Hamiltonians and on Bose-Hubbard systems, establish the competitiveness of the method.  (11/2014)

Characterization of Bose-Hubbard models with quantum nondemolition measurements

Published in Physical Review A, as editors suggestion!

We propose a scheme for the detection of quantum phase transitions in the one-dimensional (1D) Bose-Hubbard (BH) and 1D Extended Bose-Hubbard (EBH) models, using the nondemolition measurement technique of quantum polarization spectroscopy. We use collective measurements of the effective total angular momentum of a particular spatial mode to characterize the Mott insulator to superfluid phase transition in the BH model and the transition to a density wave state in the EBH model.We extend the application of collective measurements to the ground states at various deformations of a superlattice potential. (10/14)

Interference of two Bose-Einstein Condensates

Recently we have been able to create multiple BECs using a tightly focussed 'dimple' laser beam. The image to the left shows the interference of these two condensates after releasing them from their traps. We are able to change the initial separation of the condensates and observe how the interference fringe spacing changes. (09/2014)

Welcome to Mario

Mario Napolitano joined the group in June 2014 as a post-doc having previously completed his PhD in Morgan Mitchell's group at ICFO. Mario will bring his expertise in Faraday imaging to the QM&M experiment and help set up our optical lattices. (07/14)

Welcome to Lars

Lars Kroll Kristensen joined the CODER team as a full time professional game designer. He has extensive experience in the game industry and will manage to game development process at the CODER center.

First in-situ BEC pictures using Faraday Imaging

We've been able to take 'Faraday pictures' of our BEC held in a crossed dipole trap. Instead of measuring the light absorbed by the cold atoms we detect the polarisation rotation of the imaging light. This method is much less destructive than absorption imaging and should allow us to take multiple images of the same cold cloud or BEC.

The picture is roughly 100 x 160 micrometers; the actual BEC is much smaller!

06/14

Games as a Platform for Student Participation in Authentic Scientific Research

Published in the Electronic Journal of e-Learning 

This paper presents results from the design and testing of an educational version of Quantum Moves, a Scientific Discovery Game that allows players to help solve authentic scientific challenges in the effort to develop a quantum computer. The primary aim of developing a game-based platform for student-research collaboration is to investigate if and how this type of game concept can strengthen authentic experimental practice and the creation of new knowledge in science education. Researchers and game developers tested the game in three separate high school classes (Class 1, 2, and 3). The tests were documented using video observations of students playing the game, qualitative interviews, and qualitative and quantitative questionnaires. The focus of the tests has been to study players' motivation and their experience of learning through participation in authentic scientific inquiry. In questionnaires conducted in the two first test classes students found that the aspects of doing “real scientific research” and solving physics problems were the more interesting aspects of playing the game. However, designing a game that facilitates professional research collaboration while simultaneously introducing quantum physics to high school students proved to be a challenge. A collaborative learning design was implemented in Class 3, where students were given expert roles such as experimental and theoretical physicists. This significantly improved the students’ feeling of learning physics compared to Class 1 and 2. Overall the results presented in this paper indicate that the possibility of participating in authentic scientific experiments, which this class of games opens, is highly motivating for students. The findings also show that the learning design in the class setting must be considered in order to improve the students’ experience of learning and that various design challenges remain to be addressed even further.

Welcome to Emily

Emily Dougan joined us in June as a CODER fellow after finishing her Bachelor's degree in environmental and earth science at Willamette University, Salem, USA. Emily will over the summer help shape and refine the communication strategy of the CODER project.

Time limited optimal dynamics beyond the Quantum Speed Limit

The quantum speed limit sets the minimum time required to transfer a quantum system completely into a given target state. At shorter times the higher operation speed has to be paid with a loss of fidelity. Here we quantify the trade-off between the fidelity and the duration in a system driven by a time-varying control and interpret the result in Hilbert space geometry. Formulating a necessary convergence criterion for Optimal Control (OC) algorithms allows us to implement an algorithm which minimizes the process duration while obtaining a predefined fidelity. arxiv.org/abs/1405.6079 (05/2014)

Spin dynamics in a two dimensional quantum gas

Published in Physical Review A, Rapid comm.

We have investigated spin dynamics in a 2D quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimposed  angular density modulations. The  density distributions depend on the applied magnetic field and are well explained by a simple Bogoliubov model. We  show that the two clouds are anti-correlated in momentum space. The observed momentum correlations pave the way towards the creation of an atom source with non-local Einstein-Podolsky-Rosen entanglement. (05/2014)

Welcome to Mathieu

Mathieu de Goer from the department of physics of the Ecole Normale Supérieure de Cachan joined our experiment for a summer internship. He will assist in setting up the lattices and with the testing of the non-destructive imaging of ultracold clouds. (04/2014)

Recent article selected for the front page of the PRA website

Our recent paper has been selected to appear on the PRA website as part of their Kaleidoscope feature. This means that it will feature on their front page for around a month. It appears in cycles so catch it if you can!

One- and two-qubit quantum gates using superimposed optical-lattice potentials

Published in PRA

We propose an architecture which allows for the merger of a selected qubit pair in a long-periodicity superlattice structure consisting of two optical lattices with close-lying periodicity. We numerically optimize the gate time and fidelity, including the effects on neighboring atoms and in the presence of experimental sources of error. Furthermore, the superlattice architecture induces a differential hyperfine shift, allowing for single-qubit gates. The fastest possible single-qubit gate times, given a maximal tolerable rotation error on the remaining atoms at various values of the lattice wavelengths, are identified. (03/2014)

First BEC in the new experiment

After a year and a half of hard work we finally have a BEC! Roughly 300k atoms in a hybrid trap geometry. (01/14)

Lundbeck Foundation Fellowship to Jacob Sherson

Jacob Sherson has just been awarded a Lundbeck Foundation Fellowship valued at DKK 10 million. See more details on the official news announcement.   (11/2013)

Welcome to Robert

Robert Heck joined the group in August 2013 as graduate student. Robert will be working on setting up the QM&M experiment. (08/13)

Welcome to Wenzhou

Wenzhou Zhang joined the group in March 2013. He will work on the new experiment as a postdoctoral researcher. Wenzhou previously worked at the Chinese Academy of Sciences on Bose-Fermi mixtures of ultracold atoms. (03/13)

First MOT in the new lab

On the 18th of February, the first MOT was realized in the new High Resolution Experiment. The system consists of a combined 2D and 3D MOT, and it will form the basis for creating BECs in the new experiment. (02/13)

Marie Curie Individual Fellowship

Recently Mark obtained a Marie Curie Fellowship. Mark works as a postdoctoral researcher on setting up the QM&M experiment. Congratulations to Mark! (12/12)

Welcome to Mark

In JulyMark Bason joined our group as a postdoctoral researcher. In the coming years he will work on the QM&M experiment. (07/2012)

Welcome to Romain

In May our group was joined by Romain Müller, who will set up the new HiRes experiment. Romain previously worked on cooling of bosonic cesium and fermionic lithium at Heidelberg University. We all look forward to the exciting start of a new experiment. (05/2012)

Aarhus University Research Foundation funds, AU Ideas Center for Community Driven Research (CODER)

We have just been awarded funding for a three-year interdisciplinary center, CODER, within which we will develop online games allowing users of the internet to contribute to solving actual scientific challenges in the field of quantum physics. As a first challenge we will attempt to assist the players in finding new and more efficient solutions for the realization of quantum gates in a quantum computation architecture based on moving atoms in a lattice around in a focussed tweezer of light. (12/11)

Jacob Sherson receives Steno grant

The prestigious Steno grant is awarded by the Free Research Council (Det Frie Forskningsråd) in the Nature and Universe (FNU) division. It is a four year grant and will allow Jacob Sherson to establish a new research activity in the field of cold atomic gases. (12/10)