32 research outputs found
A high-fidelity photon gun: intensity-squeezed light from a single molecule
A two-level atom cannot emit more than one photon at a time. As early as the
1980s, this quantum feature was identified as a gateway to "single-photon
sources", where a regular excitation sequence would create a stream of light
particles with photon number fluctuations below the shot noise. Such an
intensity squeezed beam of light would be desirable for a range of applications
such as quantum imaging, sensing, enhanced precision measurements and
information processing. However, experimental realizations of these sources
have been hindered by large losses caused by low photon collection efficiencies
and photophysical shortcomings. By using a planar metallo-dielectric antenna
applied to an organic molecule, we demonstrate the most regular stream of
single photons reported to date. Measured intensity fluctuations reveal 2.2 dB
squeezing limited by our detection efficiency, equivalent to 6.2 dB intensity
squeezing right after the antenna.Comment: 9 pages, 3 figure
High-resolution spectroscopy of single Pr ions on the H-D transition
Rare earth ions in crystals exhibit narrow spectral features and
hyperfine-split ground states with exceptionally long coherence times. These
features make them ideal platforms for quantum information processing in the
solid state. Recently, we reported on the first high-resolution spectroscopy of
single Pr ions in yttrium orthosilicate (YSO) nanocrystals. While in
that work we examined the less explored H-P transition at a
wavelength of 488 nm, here we extend our investigations to the
H-D transition at 606 nm. In addition, we present measurements
of the second-order autocorrelation function, fluorescence lifetime, and
emission spectra of single ions as well as their polarization dependencies on
both transitions; these data were not within the reach of the first experiments
reported earlier. Furthermore, we show that by a proper choice of the
crystallite, one can obtain narrower spectral lines and, thus, resolve the
hyperfine levels of the excited state. We expect our results to make single-ion
spectroscopy accessible to a larger scientific community.Comment: 5 pages, 5 figure
Few-photon coherent nonlinear optics with a single molecule
The pioneering experiments of linear spectroscopy were performed using flames
in the 1800s, but nonlinear optical measurements had to wait until lasers
became available in the twentieth century. Because the nonlinear cross section
of materials is very small, usually macroscopic bulk samples and pulsed lasers
are used. Numerous efforts have explored coherent nonlinear signal generation
from individual nanoparticles or small atomic ensembles with millions of atoms.
Experiments on a single semiconductor quantum dot have also been reported,
albeit with a very small yield. Here, we report on coherent nonlinear
spectroscopy of a single molecule under continuous-wave single-pass
illumination, where efficient photon-molecule coupling in a tight focus allows
switching of a laser beam by less than a handful of pump photons nearly
resonant with the sharp molecular transition. Aside from their fundamental
importance, our results emphasize the potential of organic molecules for
applications such as quantum information processing, which require strong
nonlinearities.Comment: 6 pages, 5 figure
Coherent Interaction of Light and Single Molecules in a Dielectric Nanoguide
We present a new scheme for performing optical spectroscopy on single
molecules. A glass capillary with a diameter of 600 nm filled with an organic
crystal tightly guides the excitation light and provides a maximum spontaneous
emission coupling factor () of 18% for the dye molecules doped in the
organic crystal. Combination of extinction, fluorescence excitation and
resonance fluorescence spectroscopy with microscopy provides high-resolution
spatio-spectral access to a very large number of single molecules in a linear
geometry. We discuss strategies for exploring a range of quantum optical
phenomena, including coherent cooperative interactions in a mesoscopic ensemble
of molecules mediated by a single mode of propagating photons.Comment: 5 pages, 5 figure
Detection, spectroscopy and state preparation of a single praseodymium ion in a crystal
Solid-state emitters with atom-like optical and magnetic transitions are
highly desirable for efficient and scalable quantum state engineering and
information processing. Quantum dots, color centers and impurities embedded in
inorganic hosts have attracted a great deal of attention in this context, but
influences from the matrix continue to pose challenges on the degree of
attainable coherence in each system. We report on a new solid-state platform
based on the optical detection of single praseodymium ions via 4f intrashell
transitions, which are well shielded from their surroundings. By combining
cryogenic high-resolution laser spectroscopy with fluorescence microscopy, we
were able to spectrally select and spatially resolve individual ions. In
addition to elaborating on the essential experimental steps for achieving this
long-sought goal, we demonstrate state preparation and read out of the three
ground-state hyperfine levels, which are known to have lifetimes of the order
of hundred seconds
A Sub--Volume Cantilever-based Fabry-P\'erot Cavity
We report on the realization of an open plane-concave Fabry-P\'erot resonator
with a mode volume below at optical frequencies. We discuss some of
the less common features of this new microcavity regime and show that the
ultrasmall mode volume allows us to detect cavity resonance shifts induced by
single nanoparticles even at quality factors as low as . Being based on
low-reflectivity micromirrors fabricated on a silicon cantilever, our
experimental arrangement provides broadband operation, tunability of the cavity
resonance, lateral scanning and promise for optomechanical studies
Coherent coupling of single molecules to on-chip ring resonators
We report on cryogenic coupling of organic molecules to ring microresonators
obtained by looping sub-wavelength waveguides (nanoguides). We discuss
fabrication and characterization of the chip-based nanophotonic elements which
yield resonator finesse in the order of 20 when covered by molecular crystals.
Our observed extinction dips from single molecules reach 22%, consistent with
the expected Purcell enhancements up to 11 folds. Future efforts will aim at
efficient coupling of a handful of molecules via their interaction with a ring
microresonator mode, setting the ground for the realization of quantum optical
cooperative effects
On-chip interference of scattering from two individual molecules in plastic
Integrated photonic circuits offer a promising route for studying coherent
cooperative effects of a controlled collection of quantum emitters. However,
spectral inhomogeneities, decoherence and material incompatibilities in the
solid state make this a nontrivial task. Here, we demonstrate efficient
coupling of a pair of organic molecules embedded in a plastic film to a TiO
microdisc resonator on a glass chip. Moreover, we tune the resonance
frequencies of the molecules with respect to that of the microresonator by
employing nanofabricated electrodes. For two molecules separated by a distance
of about 8m and an optical phase difference of about , we report
on a large collective extinction of the incident light in the forward direction
and the destructive interference of its scattering in the backward direction.
Our work sets the ground for the coherent coupling of several molecules via a
common mode and the realization of polymer-based hybrid quantum photonic
circuits
Spectral splitting of a stimulated Raman transition in a single molecule
The small cross section of Raman scattering poses a great challenge for its
direct study at the single-molecule level. By exploiting the high Franck-Condon
factor of a common-mode resonance, choosing a large vibrational frequency
difference in electronic ground and excited states and operation at T < 2K, we
succeed at driving a coherent stimulated Raman transition in individual
molecules. We observe and model a spectral splitting that serves as a
characteristic signature of the phenomenon at hand. Our study sets the ground
for exploiting the intrinsic optomechanical degrees of freedom of molecules for
applications in solid-state quantum optics and information processing.Comment: 7 pages, 5 figure