9 research outputs found
High purity bright single photon source
Using cavity-enhanced non-degenerate parametric downconversion, we have built
a frequency tunable source of heralded single photons with a narrow bandwidth
of 8 MHz, making it compatible with atomic quantum memories. The photon state
is 70% pure single photon as characterized by a tomographic measurement and
reconstruction of the quantum state, revealing a clearly negative Wigner
function. Furthermore, it has a spectral brightness of ~1,500 photons/s per MHz
bandwidth, making it one of the brightest single photon sources available. We
also investigate the correlation function of the down-converted fields using a
combination of two very distinct detection methods; photon counting and
homodyne measurement.Comment: 9 pages, 4 figures; minor changes, added referenc
Directly estimating non-classicality
We establish a method of directly measuring and estimating non-classicality -
operationally defined in terms of the distinguishability of a given state from
one with a positive Wigner function. It allows to certify non-classicality,
based on possibly much fewer measurement settings than necessary for obtaining
complete tomographic knowledge, and is at the same time equipped with a full
certificate. We find that even from measuring two conjugate variables alone,
one may infer the non-classicality of quantum mechanical modes. This method
also provides a practical tool to eventually certify such features in
mechanical degrees of freedom in opto-mechanics. The proof of the result is
based on Bochner's theorem characterizing classical and quantum characteristic
functions and on semi-definite programming. In this joint
theoretical-experimental work we present data from experimental optical Fock
state preparation, demonstrating the functioning of the approach.Comment: 4+1 pages, 2 figures, minor change
Time gating of heralded single photons for atomic memories
We demonstrate a method for time gating the standard heralded continuous-
wave (cw) spontaneous parametric down-converted (SPDC) single photon source by
using pulsed pumping of the optical parametric oscillator (OPO) below
threshold. The narrow bandwidth, high purity, high spectral brightness and the
pseudo-deterministic character make the source highly suitable for light-atom
interfaces with atomic memories.Comment: Accepted for publication in Optics Letter
Optoelectronic cooling of mechanical modes in a semiconductor nanomembrane
Optical cavity cooling of mechanical resonators has recently become a
research frontier. The cooling has been realized with a metal-coated silicon
microlever via photo-thermal force and subsequently with dielectric objects via
radiation pressure. Here we report cavity cooling with a crystalline
semiconductor membrane via a new mechanism, in which the cooling force arises
from the interaction between the photo-induced electron-hole pairs and the
mechanical modes through the deformation potential coupling. The optoelectronic
mechanism is so efficient as to cool a mode down to 4 K from room temperature
with just 50 uW of light and a cavity with a finesse of 10 consisting of a
standard mirror and the sub-wavelength-thick semiconductor membrane itself. The
laser-cooled narrow-band phonon bath realized with semiconductor mechanical
resonators may open up a new avenue for photonics and spintronics devices.Comment: 5 pages, 4 figure