32 research outputs found
Tunable Whispering Gallery Mode Resonators for Cavity Quantum Electrodynamics
We theoretically study the properties of highly prolate shaped dielectric
microresonators. Such resonators sustain whispering gallery modes that exhibit
two spatially well separated regions with enhanced field strength. The field
per photon on the resonator surface is significantly higher than e.g. for
equatorial whispering gallery modes in microsphere resonators with a comparable
mode volume. At the same time, the frequency spacing of these modes is much
more favorable, so that a tuning range of several free spectral ranges should
be attainable. We discuss the possible application of such resonators for
cavity quantum electrodynamics experiments with neutral atoms and reveal
distinct advantages with respect to existing concepts.Comment: 4 pages, 3 figure
Giant diffusion of nanomechanical rotors in a tilted washboard potential
We present an experimental realization of a biased optical periodic potential
in the low friction limit. The noise-induced bistability between locked
(torsional) and running (spinning) states in the rotational motion of a
nanodumbbell is driven by an elliptically polarized light beam tilting the
angular potential. By varying the gas pressure around the point of maximum
intermittency, the rotational effective diffusion coefficient increases by more
than 3 orders of magnitude over free-space diffusion. These experimental
results are in agreement with a simple two-state model that is derived from the
Langevin equation through using timescale separation. Our work provides a new
experimental platform to study the weak thermal noise limit for diffusion in
this system
All-optical switching and strong coupling using tunable whispering-gallery-mode microresonators
We review our recent work on tunable, ultrahigh quality factor
whispering-gallery-mode bottle microresonators and highlight their applications
in nonlinear optics and in quantum optics experiments. Our resonators combine
ultra-high quality factors of up to Q = 3.6 \times 10^8, a small mode volume,
and near-lossless fiber coupling, with a simple and customizable mode structure
enabling full tunability. We study, theoretically and experimentally, nonlinear
all-optical switching via the Kerr effect when the resonator is operated in an
add-drop configuration. This allows us to optically route a single-wavelength
cw optical signal between two fiber ports with high efficiency. Finally, we
report on progress towards strong coupling of single rubidium atoms to an
ultra-high Q mode of an actively stabilized bottle microresonator.Comment: 20 pages, 24 figures. Accepted for publication in Applied Physics B.
Changes according to referee suggestions: minor corrections to some figures
and captions, clarification of some points in the text, added references,
added new paragraph with results on atom-resonator interactio
Towards quantum computing with single atoms and optical cavities on atom chips
We report on recent developments in the integration of optical
microresonators into atom chips and describe some fabrication and
implementation challenges. We also review theoretical proposals for quantum
computing with single atoms based on the observation of photons leaking through
the cavity mirrors. The use of measurements to generate entanglement can result
in simpler, more robust and scalable quantum computing architectures. Indeed,
we show that quantum computing with atom-cavity systems is feasible even in the
presence of relatively large spontaneous decay rates and finite photon detector
efficiencies.Comment: 14 pages, 6 figure
Magneto-optical spectroscopy of charged CdSe nanocrystals
International audienc
Progress towards optical frequency standards based on two-photon transitions in atomic silver
International audienc
Spontaneous spectral diffusion in CdSe quantum dots
Spectral diffusion of the emission line of single colloidal nanocrystals is generally regarded as a random process. Here, we show that each new spectral position has a finite memory of previous spectral positions, as evidenced by persistent anticorrelations in time series of spectral jumps. The anticorrelation indicates that there is an enhanced probability of the charge distribution around the nanocrystal returning to a previous configuration. We show both statistically and directly that this memory manifests as an observable spontaneous "relaxation" in the absence of a pump laser, so that spectral diffusion progresses in a manner of "two steps forward and one step back"
Magneto-optical properties of trions in non-blinking charged nanocrystals reveal an acoustic phonon bottleneck
Charged quantum dots provide an important platform for a range of emerging quantum technologies. Colloidal quantum dots in particular offer unique advantages for such applications (facile synthesis, manipulation and compatibility with a wide range of environments), especially if stable charged states can be harnessed in these materials. Here we engineer the CdSe nanocrystal core and shell structure to efficiently ionize at cryogenic temperatures, resulting in trion emission with a single sharp zero-phonon line and a mono exponential decay. Magneto-optical spectroscopy enables direct determination of electron and hole g-factors. Spin relaxation is observed in high fields, enabling unambiguous identification of the trion charge. Importantly, we show that spin flips are completely inhibited for Zeeman splittings below the low-energy bound for confined acoustic phonons. This reveals a characteristic unique to colloidal quantum dots that will promote the use of these versatile materials in challenging quantum technological applications