PRL Editors’ Choice for ITP work

Myung-Joong, Ricardo and Martin have published work showing that a two-level atom coupled to a single-mode cavity field undergoes a second order quantum phase transition when the atomic transition frequency is much larger than the cavity frequency. This result has been chosen as an Editor Suggestion in Physical Review Letters.
You can read the full details in
Quantum Phase Transition and Universal Dynamics in the Rabi Model
Myung-Joong Hwang, Ricardo Puebla, and Martin B. Plenio
Phys. Rev. Lett. 115, 180404 (2015) – Published 29 October 2015


Their work shows that superradiant quantum phase transitions, which are generally studied for systems of thermodynamically many atoms, can actually be investigated within systems containing just a single atom and a single radiation mode. The limit of larger particle number, normally considered as the thermodynamics limit, is replaced by a limit in the coupling strength such that an increasingly large Hilbert space becomes accessible. To confirm that the system behaves like a critical system they studied the Kibble-Zurek mechanism and saw all the right scaling relations.

ITP work published in Nature Communications

Theoretical predictions by Jaemin, Felipe, Susana and Martin to explain long-lasting quantum coherence in photosynthetic systems have been tested in an experiment using an artificial light harvester. These results were published in Nature Communications on 9 July 2015 and provide the first unambiguous demonstration of the relevance of vibronic effects for the persistence of coherent response in molecular aggregates.

Together with colleagues from Vienna University of Technology (Austria), Lund University (Sweden), Charles University in Prague (Czech Republic), Universidad Politécnica de Cartagena (Spain) and Freie Universität Berlin (Germany) they investigated an artificial molecular light-harvester, a J-aggregate of cyanine dyes. The relatively simple electronic and vibrational structure of the artificial light-harvester reduced the complexity of two-dimensional electronic spectra significantly and allowed to test different theoretical models quantitatively, showing that the coherent interaction between intramolecular vibrations and electronic degrees of freedom induces long-lasting quantum coherences, which provided quantitative agreement with their experimental observations.


You can read all details in J. Lim, D. Paleček, F. Caycedo-Soler, C. N. Lincoln, J. Prior, H. von Berlepsch, S. F. Huelga, M. B. Plenio, D. Zigmantas, and J. Hauer, Vibronic origin of long-lived coherence in an artificial molecular light harvester, Nature Communications 6, 7755 (2015).

Winter Semester 2015/16 kicks off

And with it, the Monday faculty colloquium. Hosted by Wolfgang Schleich, the first speaker this season has been Prof. Wojciech Zurek, Einstein Professor at Ulm University and a researcher at Los Alamos State Laboratory. Besides revising some aspects of his well-known theory of decoherence, Wojciech presented his approach to a minimal derivation of the quantum formalism in terms of the concept of “Envariance” (Environment assisted invariance) of composite quantum states. This allows for Born rule to feature as derived result rather than an additional postulate. There were plenty of questions and agitated discussions showing that nothing stimulates physicists more than a good dose of foundations. You can check the technical details of Wojciech work’s on the concept of envariance in   W. H. Zurek, Probabilities from entanglement, Borns rule from envariance, quant-ph/0405161, Phys. Rev. A 71, 052105 (2005) .

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Andreas Albrecht has defended his PhD thesis in July 2015. He was awarded the title with distinction and is now in his way to Barcelona to join the group of Theoretical Quantum-Nano Photonics at ICFO led by Prof. Dr. Darrick Chang.

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Andreas’ viva provided yet another occasion to display an incredible piece of PhD hat craftsmanship and was followed by a degustation of delicious super-Pretzel to feed the entire group.


Andreas later received a special farewell present with the award of the PhD Prize of the SFB/TRR 21 “Control of Quantum Correlations in Tailored Matter”. Further handmade cakes were provided to celebrate the good news and the start of his postdoc position in Barcelona.

Tillmann Baumgratz defended his PhD thesis and was awarded the PhD with a Distinction. Now he is off to new shores,  taking up a postdoctoral position at Clarendon Laboratory, Oxford University, to work in the group of Animesh Datta. The amazing graduation hat was designed by his office mates, Andreas and Robert, and had some tomography component plus a reminder of a snowboarding mishap (never try to impress your girlfriend too much) during his time with us. Fortunately, there is no (much) snow in Oxford…

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Sarah Pomiersky completed her Master thesis under the supervision of Chris Schroeder and Martin Plenio. Good occasion to celebrate with our favourite Quarkkuchen from the Ulmer Zuckerbäcker. Sarah decided to move to the real world to pursuing a career in industry or consulting. We still hope that she may not like it and be back! 

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Debora Contreras has been awarded a long term fellowship to join the Institute of Physics at the UNAM, in Mexico DF. This is the first step to become a permanent member of staff and we congratulate Debora warmly on the success. Cecilia Cormick has also returned to Latin-American to take up a research position the Universidad Nacional de Cordoba in her native Argentina. Jianming Cai is also on the move after having accepted a Full Professor position at the University of Wuham in China. We are very happy that also Cecilia and Jianming will continue their careers in academia. movers9





<= Cecilia explains the intricacies of “alfajores” to a concentrated north American audience (Chris Schroeder and Nathan Killoran).
Thanks to Debora we got to know some amazing Mexican sweets:

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The LH1-like coconut ring has achieved cult status in the seminar board…
Jianming was the official liaison officer with our favourite Chinese restaurant in Ulm. We look forward to his next visit so that to properly celebrate his new position in China with a delicious Peking duck with pancakes.

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Abolfazl Bayat , on the left, is now back in London, working with Sougato Bose in UCL.

ITP publishes another work in Nature Communications

Colour centers in diamond are very sensitive magnetic field sensors. Just how sensitivewas demonstrated by Fedor Jelezko and his team together with Jianming and Martin. Implanting a single NV colour center just 2nm below the surface they were able to observe the magnetic field of just a few silicon nuclear spins. This feat became possible by using state-of-the-art noise decoupling sequences and advanced methods of signal processing which allowed the team to extract the relevant information from a noisy signal. This is another step towards the holy grail of examining protein structure by means of diamond sensors. For the complete story go to Nature Communications 4, 3704 (2014)

ITP work published in Nature Communications

Nature Communications publishes an article in which Jianming, Fedor and Martin propose a hybrid sensor composed of a colour centre in diamond which is covered by a piezomagnetic material. The resulting device promises a sensitivity for pressure and force that is three orders of magnitude increased compared to a colour centre in diamond. The very same design may also lead to the same enhancement for electron spin-vibrational coupling thus providing new routes to the design of nanomechanical systems. You can read the complete story in Nature Communications 5, 4065 (2014).

ITP work is chosen as Editor’s Suggestion in PRL

Our recent article “Extracting Entanglement from Identical Particles,” by Nathan, Marcus, and Martin, has been highlighted as an Editor’s Suggestion in the most recent volume of Physical Review Letters. This distinction recognizes papers which are particularly well-written and of broad interest to readers from many fields of physics. In this work, we show how the intrinsic entanglement of identical particles can be extracted and put to use for practical quantum information tasks. The article can be found at