67 research outputs found
Heralded single phonon preparation, storage and readout in cavity optomechanics
We analyze theoretically how to use the radiation pressure coupling between a
mechanical oscillator and an optical cavity field to generate in a heralded way
a single quantum of mechanical motion (a Fock state), and release on-demand the
stored excitation as a single photon. Starting with the oscillator close to its
ground state, a laser pumping the upper motional sideband leads to dynamical
backaction amplification and to the creation of correlated photon-phonon pairs.
The detection of one Stokes photon thus projects the macroscopic oscillator
into a single-phonon Fock state. The non-classical nature of this mechanical
state can be demonstrated by applying a readout laser on the lower sideband
(i.e. optical cooling) to map the phononic state to a photonic mode, and by
performing an autocorrelation measurement on the anti-Stokes photons. We
discuss the relevance of our proposal for the future of cavity optomechanics as
an enabling quantum technology.Comment: Accepted for publication in Physical Review Letters. Added References
42,4
Molecular cavity optomechanics: a theory of plasmon-enhanced Raman scattering
The conventional explanation of plasmon-enhanced Raman scattering attributes
the enhancement to the antenna effect focusing the electromagnetic field into
sub-wavelength volumes. Here we introduce a new model that additionally
accounts for the dynamical and coherent nature of the plasmon-molecule
interaction and thereby reveals an enhancement mechanism not contemplated
before: dynamical backaction amplification of molecular vibrations. We first
map the problem onto the canonical model of cavity optomechanics, in which the
molecular vibration and the plasmon are \textit{parametrically coupled}. The
optomechanical coupling rate, from which we derive the Raman cross section, is
computed from the molecules Raman activities and the plasmonic field
distribution. When the plasmon decay rate is comparable or smaller than the
vibrational frequency and the excitation laser is blue-detuned from the plasmon
onto the vibrational sideband, the resulting delayed feedback force can lead to
efficient parametric amplification of molecular vibrations. The optomechanical
theory provides a quantitative framework for the calculation of enhanced
cross-sections, recovers known results, and enables the design of novel systems
that leverage dynamical backaction to achieve additional, mode-selective
enhancement. It yields a new understanding of plasmon-enhanced Raman scattering
and opens a route to molecular quantum optomechanics.Comment: Extensively revised and improved version thanks to the hard work and
constructive comments of a careful Referee. Includes Supplemental Materia
Geometric phases in discrete dynamical systems
In order to study the behaviour of discrete dynamical systems under adiabatic
cyclic variations of their parameters, we consider discrete versions of
adiabatically-rotated rotators. Paralleling the studies in continuous systems,
we generalize the concept of geometric phase to discrete dynamics and
investigate its presence in these rotators. For the rotated sine circle map, we
demonstrate an analytical relationship between the geometric phase and the
rotation number of the system. For the discrete version of the rotated rotator
considered by Berry, the rotated standard map, we further explore this
connection as well as the role of the geometric phase at the onset of chaos.
Further into the chaotic regime, we show that the geometric phase is also
related to the diffusive behaviour of the dynamical variables and the Lyapunov
exponent
Measurement and shaping of biphoton spectral wavefunctions
In this work we present a simple method to reconstruct the complex spectral
wavefunction of a biphoton, and hence gain complete information about the
spectral and temporal properties of a photon pair. The technique, which relies
on quantum interference, is applicable to biphoton states produced with a
monochromatic pump when a shift of the pump frequency produces a shift in the
relative frequencies contributing to the biphoton. We demonstrate an example of
such a situation in type-II parametric down-conversion (SPDC) allowing
arbitrary paraxial spatial pump and detection modes. Moreover, our test cases
demonstrate the possibility to shape the spectral wavefunction. This is
achieved by choosing the spatial mode of the pump and of the detection modes,
and takes advantage of spatiotemporal correlations.Comment: Supplementary information also available. Comments and feedback
appreciated. Compared to the previous version, here we have made the
following changes: -corrected a typo in the text between Eq. (11) and (12)
-corrected a typo in the references -added reference
A tunable narrowband entangled photon pair source for resonant single-photon single-atom interaction
We present a tunable, frequency-stabilized, narrow-bandwidth source of
frequency-degenerate, entangled photon pairs. The source is based on
spontaneous parametric downconversion (SPDC) in periodically-poled KTiOPO4
(PPKTP). Its wavelength can be stabilized to 850 or 854 nm, thus allowing to
address two D-P transitions in 40Ca+ ions. Its output bandwidth of 22 MHz
coincides with the absorption bandwidth of the calcium ions. Its spectral power
density is 1.0 generated pairs/(s MHz mW).Comment: 3 pages, 3 figure
Geometric Mixing, Peristalsis, and the Geometric Phase of the Stomach
Mixing fluid in a container at low Reynolds number - in an inertialess
environment - is not a trivial task. Reciprocating motions merely lead to
cycles of mixing and unmixing, so continuous rotation, as used in many
technological applications, would appear to be necessary. However, there is
another solution: movement of the walls in a cyclical fashion to introduce a
geometric phase. We show using journal-bearing flow as a model that such
geometric mixing is a general tool for using deformable boundaries that return
to the same position to mix fluid at low Reynolds number. We then simulate a
biological example: we show that mixing in the stomach functions because of the
"belly phase": peristaltic movement of the walls in a cyclical fashion
introduces a geometric phase that avoids unmixing.Comment: Revised, published versio
The Young and Bright Type Ia Supernova ASASSN-14lp: Discovery, Early-Time Observations, First-Light Time, Distance to NGC 4666, and Progenitor Constraints
On 2014 Dec. 9.61, the All-Sky Automated Survey for SuperNovae (ASAS-SN or
"Assassin") discovered ASASSN-14lp just days after first light using a
global array of 14-cm diameter telescopes. ASASSN-14lp went on to become a
bright supernova ( mag), second only to SN 2014J for the year. We
present prediscovery photometry (with a detection less than a day after first
light) and ultraviolet through near-infrared photometric and spectroscopic data
covering the rise and fall of ASASSN-14lp for more than 100 days. We find that
ASASSN-14lp had a broad light curve (), a
-band maximum at , a rise time of days, and moderate host--galaxy extinction (). Using ASASSN-14lp we derive a distance modulus for NGC 4666 of
corresponding to a distance of Mpc.
However, adding ASASSN-14lp to the calibrating sample of Type Ia supernovae
still requires an independent distance to the host galaxy. Finally, using our
early-time photometric and spectroscopic observations, we rule out red giant
secondaries and, assuming a favorable viewing angle and explosion time, any
non-degenerate companion larger than .Comment: 12 pages, 9 figures, 4 tables. Accepted to ApJ. Photometric data
presented in this submission are included as an ancillary file. For a brief
video explaining this paper, see https://www.youtube.com/watch?v=1bOV-Cqs-a
Drug-Initiated Synthesis of Cladribine-Based Polymer Prodrug Nanoparticles: Biological Evaluation and Structure Activity Relationships
International audienceBy using two reversible deactivation radical polymerization techniques, either nitroxide-mediated polymerization or reversible addition-fragmentation chain transfer polymerization, the "drug-initiated" approach was applied to cladribine (CdA) as an anticancer drug to synthesize small libraries of well-defined and self-stabilized CdA-based polymer prodrug nanoparticles, differing from the nature and the molar mass of the grown polymer, and the nature of the linker between CdA and the polymer, thus allowing structure-cytotoxicity relationships to be determined. Their biological evaluation was investigated in vitro on L1210 cancer cells. The preparation of fluorescent CdA-based nanoparticles with excellent imaging ability was also reported by applying the "drug-initiated" approach to an aggregation-induced emission-active dye
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