Dr. Stephan Dürr
Stephan Dürr
Telefon: +49 89 3 29 05 - 291
Dr. Johannes Kofler
Johannes Kofler
Telefon: +49 89 3 29 05 - 242



Die Gastvorträge im Rahmen des MPQ-Kolloquiums finden von April bis Juli sowie von Oktober bis Januar jeweils dienstags um 14:30 Uhr im Herbert-Walther-Hörsaal des Max-Planck-Instituts für Quantenoptik statt.

Ansprechpartner für die wissenschaftliche Organisation:

Dr. Stephan Dürr und Dr. Johannes Kofler

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Single spins in diamond: from quantum computers to atomic sensors

Diamond is not only the king gemstone, but also a promising material in modern technology (which holds a promise to replace silicon) owing tounprecedented thermal conductivity, high charge carrier mobility and chemical inertness. Less known is that defects in diamond can be used for quantum information processing. Owing to their remarkable stability, colour centers in diamond have already found an application in quantum cryptography. Furthermore, it was shown that spin states associated with single nitrogen-vacancy defects can be detected optically. In this talk I will discuss recent progress regarding spin-based quantum information processing and atomic magnetometry using single spins in diamond. [mehr]

Laser-driven atoms in a nano-lattice rebel against uniformity

On a sub-wavelength scale, atoms in a crystal, i. e. an ordered lattice, are normally assumed to be almost uniformly excited by an incident light. An interatomic interaction produces then a uniform local field (different from that of incident laser) at each atom as well. This is a major assumption in the Lorentz-Lorenz theory of interaction of light with dense matter. We showed [1] that at certain critical conditions on the atomic density and dipole strength, a previously unexpected phenomenon emerges: the interacting atoms break the uniformity of interaction, and in a violent switch to a strong non-uniformity, their excitation and local field form nanoscale strata with a spatial period much shorter than that of laser wavelength, thus changing the entire paradigm of light-matter interaction. The most interesting effects can be observed for relatively small 1D-arrays or 2D lattices if the laser is almost resonant to an atomic quantum transition. The effects include huge local field enhancement at size-related resonances at the frequencies near the atomic line, so that the strata are readily controlled by laser tuning. A striking feature is that for the shortest strata, the nearest atomic dipoles counter-oscillate, which is reminiscent of anti-ferromagnetism of magnetic dipoles in Ising model. [mehr]

Recent progress in quantum control of trapped ions

The push to implement quantum information processing (QIP) with trapped ions has led to a number of technological advances that can be leveraged towards this goal, but also allow for novel experimental approaches outside the original scope. The most spectacular example for the latter is the quantum-logic ion clock, at present the most precise frequency standard, with potential for further improvement. This talk will cover some of the recent advances in QIP with trapped ions at NIST and give a few examples besides the quantum logic ion clock that illustrate the potential of trapped ions for quantum simulations of complex designer Hamiltonians, quantum limited measurements and high resolution spectroscopy. [mehr]

Quantum Magnetism with Ultracold Atoms

Understanding the behaviors of strongly-interacting spin systems is one of the central objectives of modern manybody quantum physics. I will present experiments in which we have realized quantum magnetism with ultracold atoms in an optical lattice. We carry out a quantum simulation of an Ising spin chain and demonstrate a quantum phase-transition from a paramagnetic phase to an anti-ferromagnetic phase.The magnetic phases are detected in situ through our quantum gas microscope. This work opens a wide range of new possibilities for studying quantum magnetism. Exotic states of matter and frustrated spin physics in optical lattices are now within experimental reach. [mehr]

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