Project Outline

Our modern, knowledge-based society relies on fast and efficient processing of information. Conventional electronic data storage and processing are already about to reach their limits in terms of capacities and processor rates. Thus, we require novel approaches to store and process large amounts of information at high performance. Modern quantum optics already provides some basic strategies to reach these goals. We note here, e.g., the concepts of quantum memories, qubits, entanglement, quantum computation, quantum cryptography, or single photon sources.

Many of these approaches rely on interactions between coherent radiation and quantized matter. As a specific class of coherent interactions, adiabatic passage processes combine high efficiency and pronounced robustness with regard to fluctuations in the experimental parameters. Electromagnetically-induced transparency (EIT) exhibits a prominent example for such adiabatic interactions. EIT triggered the development of many novel concepts for optical information storage. This led to the implementation of ultra-slow light, storage of light pulses in atomic coherences, and quite recently the concept of stationary light pulses (SLPs). SLPs may be understood as “freezing” or “trapping” radiation in an appropriately driven atomic medium. This is similar to storage of light in a laser cavity – but without the need for mirrors. All EIT-based effects significantly increase the interaction time of photons with the medium. Thus, also the interaction time between photons from additional radiation fields in the medium increases. At the same time incoherent absorption by the medium is suppressed.

The concepts of EIT, slow light, or light storage/retrieval have been extensively studied experimentally. In contrast, the quite novel concept of SLPs received only little experimental attention so far. Among others, this is due to the large optical depth required for the formation of SLPs.

While experimental investigations on SLPs are still very rare, theoretical studies already predicted a number of surprising phenomena related to SLPs. Examples are the generation of entangled wave packets, Bose-Einstein condensation of stationary light polaritons, and (maybe most strikingly) the “crystallization” of photons. In the latter case, strongly correlated bosonic photons experience a transition towards a fermionic regime, i.e., the photons repulse each other. The generation of such a quantum gas of “crystallized” photons, with full control of their interaction, provides alternative access to studies of strongly correlated quantum systems - which are of significant interest to contemporary physics. Moreover, SLPs permit strong nonlinear optical processes at the level of few photons. This enables, e.g., the development of novel switches for quantum information networks. These selected examples already indicate the potential of SLPs for quantum optics, quantum information, and strongly correlated media. Detailed experimental investigations are required to determine possibilities and limitations of SLPs for future applications.

  • "Stationary Light In Cold Atoms" (SLICA) deals with the experimental implementation, investigation and application of stationary light pulses. This requires cold atoms, prepared at large optical depth, i.e., a quite exotic type of matter – and a technological challenge. Thus, SLICA aims at a combination of new technological approaches with background in cold matter and novel, powerful concepts of quantum optics.

Technological Developments

As outlined above, SLPs and related phenomena require strong coupling between light and matter, i.e., media of large optical depth OD. A new technology, which is expected to provide very large optical depths OD > 1000, uses cold atoms guided from a magneto-optical trap (MOT) into a hollow-core photonic crystal fiber (HC-PCF). An optical dipole trap in the fiber serves to avoid collisions of the atoms with the walls. Additional radiation fields are coupled into the fiber, to drive coherent optical interactions (e.g., EIT or SLPs). The setup combines tight confinement of atoms and driving radiation fields in the fiber with a long interaction length along the fiber. This enables investigations of light-matter interactions at low photon numbers and/or small atom numbers. This is of significant technological interest for applications of coherent interactions.

In the first stage of the project we will implement such a medium of high OD by loading laser-cooled atoms from a MOT into a hollow-core optical fiber. In contrast to previous setups our approach will allow for cooling during the transfer from the MOT into the dipole trap. According to numerical simulations the setup is expected to provide unprecedented optical depth in the gas phase and therefore permit the efficient generation of SLPs at very long time scales in the future. This will be equivalent to the preparation of an “all-optical cavity” with large Q-factor in the cold medium.

Publications

[1] Thorsten Peters, Svetoslav S. Ivanov, Daniel Englisch, Andon A. Rangelov, Nikolay V. Vitanov, and Thomas Halfmann,
"Variable ultrabroadband and narrowband composite polarization retarders"
Opens external link in new windowApplied Optics 51, 7466 (2012).

[2] Svetoslav S. Ivanov, Andon A. Rangelov, Nikolay V. Vitanov, Thorsten Peters, and Thomas Halfmann,
"Highly efficient broadband conversion of light polarization by composite retarders"
Opens external link in new windowJournal of the Optical Society of America A 29, 265–269 (2012).

[3] Thorsten Peters, Shih-Wei Su, Yi-Hsin Chen, Jian-Siung Wang, Shih-Chuan Gou, and Ite A. Yu,
"Formation of stationary light in a medium of nonstationary atoms"
Opens external link in new windowPhysical Review A 85, 023838 (2012).

[4] Thorsten Peters, Benjamin Wittrock, Frank Blatt, Thomas Halfmann, and Leonid Yatsenko,
"Thermometry of ultracold atoms by electromagnetically induced transparency"
Opens external link in new windowPhysical Review A 85, 063416 (2012).

[5] Frank Blatt, Thomas Halfmann, and Thorsten Peters,
"One-dimensional ultracold medium of extreme optical depth"
Opens external link in new windowOptics Letters 39, 446 (2014).

Join Our Team

If you are interested in joining our team, please click here for information on BSc/MSc projects.

Contact

Dr. Thorsten Peters (click for CV)

Nichtlineare Optik/Quantenoptik
Institut für Angewandte Physik
Fachbereich 05 - Physik
Technische Universität Darmstadt
Hochschulstr. 6
D-64289 Darmstadt

+49 6151 16-64377

+49 6151 16-4123

thorsten.peters@physik.tu-...

Contact

Prof. Dr. Thomas Halfmann
Nichtlineare Optik/Quantenoptik
Institut für Angewandte Physik
Fachbereich 05 - Physik
Technische Universität Darmstadt
Hochschulstr. 6
D-64289 Darmstadt

+49 6151 16-20740

+49 6151 16-20741 (Sekretariat)

+49 6151 16-20327

thomas.halfmann@physik.tu-...

T. Halfmann on ResearcherID

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