Quantum Information Processing
In the Quantum Information Processing team, we investigate the implementation of quantum information protocols with single, neutral atoms and photons in optical cavities. Recently, we have implemented quantum gates between atoms and photons, using the state-dependent phase shift upon reflection of a photon from the cavity. We have demonstrated an atom-photon gate, a photon-photon gate, and the nondestructive detection of photons with this mechanism.
These results are one example for the capabilities our systems offer to study and exploit interactions of light and matter in the quantum regime. While photons are excellent carriers of quantum states for large distance transmission, the long coherence times of trapped ultracold atoms are optimal for the storage of quantum information. The strong coupling achievable in our cavity quantum electrodynamics (cavity QED) systems make them ideally suited for the implementation of deterministic quantum interfaces.
Our setups allow for full control over an atom residing inside a cavity as well as overall optical fields to which the atom is exposed. With these tools for quantum engineering at hand, we develop universal light-matter quantum interfaces that efficiently couple single photons to single atoms. We routinely produce streams of single photons, whose shape, frequency, direction, polarization, and phase can independently be controlled. The cavity not only serves as an integral part of the photon creation process but also allows for the efficient and in principle deterministic emission into a well-defined spatial mode. A time reversal of the photon-creation process yields a single-atom quantum memory for photonic polarization qubits.
We also investigate the possibilities to extend our systems to multiple single atoms in one cavity. We are able to reliably load two single atoms into our cavity and determine their phase relation with which they couple to an external laser field and the cavity mode. This will allow us to implement quantum information protocols with multiple atoms.
For future experiments, we also develop fiber-based Fabry–Perot cavities that feature small mode volumes and small physical sides and therefore allow new geometries with multiple cavities. Atom-cavity systems are naturally at the heart of intriguing concepts for quantum computing and quantum communication. Along these lines, we realized an elementary quantum network comprised of two nodes. In this context, we investigated the building blocks of distributed quantum networks, such as quantum state transfer and remote entanglement generation.
- Quantum gates between atoms and photons
- Quantum networks
- Quantum memories
- Next-generation cavity QED systems
- Beyond single atom cavity QED
- Quantum control of single atoms inside a cavity
- Earlier experiments on light-matter quantum interfaces
If you are interested in joining our team as a PhD student, have a look at the job description.
January 2017: We welcome Dr. Lin Li to the Quantum Dynamics Division! This month, Lin joins the QIP team as a postdoc.
July 2016: " A photon-photon quantum gate based on a single atom in an optical resonator" by B. Hacker, S. Welte et al. has been published in Nature. Full-text access to a view-only version of the paper is available via this link. More information for the general audience can be found in our MPQ press release or in an article on the web page of the Max Planck Society..
April 2016: We welcome Severin Daiss to the Quantum Dynamics Division! This month, Severin is starting as a PhD student with the QIP team.
March 2016: " An integrated quantum repeater at telecom wavelength with single atoms in optical fiber cavities" by M. Uphoff et al. has been published in Applied Physics B.
February 2016: " Interference and dynamics of light from a distance-controlled atom pair in an optical cavity" by A. Neuzner et al. has been published in Nature Photonics. More information for the general audience can be found in our MPQ press release or in a research news article on the web page of the Max Planck Society.
December 2015: " Cavity-based quantum networks with single atoms and optical photons" by A. Reiserer et al. has been published in Review of Modern Physics.
November 2015: " Breakdown of atomic hyperfine coupling in a deep optical-dipole trap" by A. Neuzner et al. has been published in Physical Review A, and has been highlighted as an Editors' Suggestion.
November 2015: We welcome Stefan Langenfeld to the Quantum Dynamics Division! This month, Stefan is starting as a PhD student with the QIP team.
October 2015: Manuel Brekenfeld wins one of four best poster prizes at the 600. Wilhelm and Else Hereaus-Seminar “Frontiers of Quantum Optics”. He was awarded the honour to present the subject of his poster “Frequency splitting of polarization eigenmodes in fibre-based Fabry-Perot cavities” in a talk of 20 minutes duration and received prize money in the amount of 75 EUR.
August 2015: Andreas Neuzner wins the best poster award sponsored by Applied Physics B at the NIM Conference on Resonator QED. His contribution on "Quantum dynamics in spatially resolved two-atom cavity QED" was chosen on the basis of scientific content, clarity of presentation and attractiveness of design, and was honored with prize money in the amount of 200 EUR.
June 2015: " Heralded Storage of a Photonic Quantum Bit in a Single Atom" by N. Kalb et al. has been published in Physical Review Letters. A synopsis entitled "Heralded Qubit Transfer" can be found at "physics.aps.org.
April 2015: We welcome Dominik Niemietz to the Quantum Dynamics Division! This month, Dominik is starting as a PhD student with the QIP team.
January 2015: " Frequency splitting of polarization eigenmodes in microscopic Fabry–Perot cavities" by M. Uphoff et al. has been published in New Journal of Physics.
April 2014: Carolin Hahn was awarded her PhD for her work on "Remote Entanglement of Two Single Atoms".
April 2014: "A Quantum Gate between a Flying Optical Photon and a Single Trapped Atom" by A. Reiserer et al. has been published in Nature. More information for the general audience can be found in the "News & Views" article by L. Duan, in our MPQ press release or in an article on the web page of the Max Planck Society.
March 2014: Andreas Reiserer was awarded his PhD for his work on "A controlled phase gate between a single atom and an optical photon".
January 2014: We welcome Stephan Welte who will reinforce the Qgate Team!
November 2013: "Nondestructive Detection of an Optical Photon" by Andreas Reiserer et al. has been published in Science Express. We provide here free access to abstract and reprint of the manuscript. More information for the general audience can be found in our press release.
November 2013: We welcome Mahmood Sabooni in our goup! Mahmood did his PhD on quantum memories at Lund University in Sweden and is now working as a post-doc on the Qgate-Experiment.
October 2013: We welcome the new members of the QIP-team! Bastian Hacker and Josef Schupp are both joining the Qgate-Experiment for a PhD and a Master thesis, respectively. Matthias Körber is reinforcing the Photon Pistol Experiment as a PhD candidate.
September 2013: At the Conference on Resonator QED in Munich, Andreas Neuzner received the prize for the best poster presentation. The poster prize was sponsored by "Applied Physics B" and included a trophy money of 300 EUR. Gladly, Andi invested parts of it in a barrel of beer that he shared with the whole Quantum Dynamics Group!
July 2013: Christian Nölleke was awarded his PhD for his work on "Quantum state transfer between remote single atoms".
June 2013:"Generation of single photons from an atom-cavity system" by Martin Mücke et al. has been published in Physical Review A.
May 2013:"Ground-State Cooling of a Single Atom at the Center of an Optical Cavity" by Andreas Reiserer et al. has been published in Physical Review Letters. The work was highlighted in a "Synopsis - still life with atom" on the journal's webpage.
April 2013:"Efficient Teleportation Between Remote Single-Atom Quantum Memories" by Christian Nölleke et al. has been published in Physical Review Letters.
April 2012: " An elementary quantum network of single atoms in optical cavities" by Stephan Ritter et al. has been published in Nature. More information for the general audience can be found in our press release and on the websites of Science, Scientific American and IEEE Spectrum. Spektrum der Wissenschaft and Deutschlandfunk report in German.
May 2011:"A single-atom quantum memory" by Holger Specht et al. has been published in Nature. The QGate team has realized the most fundamental implementation of an optical quantum memory: Arbitrary polarization states of light can be mapped into and out of a single atom trapped inside an optical cavity, achieving an average fidelity of 93% and storage times of more than 180µs. More information for the general audience can be found in our press release.
February 2011: In a joint effort, the BEC and Pistol teams have managed to create remote entanglement between a single atom and a Bose-Einstein condensate, situated in two independent labs separated by 13m. The fidelity with a maximally entangled Bell state is 95% and the matter-matter entanglement survives for 100µs. Details can be found in our paper.