332 research outputs found
Direct observation of atomic diffusion in warm rubidium ensembles
We present a robust method for measuring the diffusion coefficients of warm
atoms in buffer gases. Using optical pumping, we manipulate the atomic spin in
a thin cylinder inside the cell. Then we observe the spatial spread of
optically pumped atoms in time using a camera, which allows us to determine the
diffusion coefficient. As an example, we demonstrate measurements of diffusion
coefficients of rubidium in neon, krypton and xenon acting as buffer gases. We
have determined the normalized (273 K, 760 Torr) diffusion coefficients to be
0.180.03 cm/s for neon, 0.070.01 cm/s for krypton, and
0.0520.006 cm/s for xenon.Comment: 6 pages, 5 figure
Phonon counting thermometry of an ultracoherent membrane resonator near its motional ground state
Generation of non-Gaussian quantum states of macroscopic mechanical objects
is key to a number of challenges in quantum information science, ranging from
fundamental tests of decoherence to quantum communication and sensing. Heralded
generation of single-phonon states of mechanical motion is an attractive way
towards this goal, as it is, in principle, not limited by the object size. Here
we demonstrate a technique which allows for generation and detection of a
quantum state of motion by phonon counting measurements near the ground state
of a 1.5 MHz micromechanical oscillator. We detect scattered photons from a
membrane-in-the-middle optomechanical system using an ultra-narrowband optical
filter, and perform Raman-ratio thermometry and second-order intensity
interferometry near the motional ground state ( phonons).
With an effective mass in the nanogram range, our system lends itself for
studies of long-lived non-Gaussian motional states with some of the heaviest
objects to date.Comment: 11 pages, 10 figure
Fast imaging of multimode transverse-spectral correlations for twin photons
Hyperentangled photonic states - exhibiting nonclassical correlations in
several degrees of freedom - offer improved performance of quantum optical
communication and computation schemes. Experimentally, a hyperentanglement of
transverse-wavevector and spectral modes can be obtained in a straightforward
way with multimode parametric single-photon sources. Nevertheless, experimental
characterization of such states remains challenging. Not only single-photon
detection with high spatial resolution - a single-photon camera - is required,
but also a suitable mode-converter to observe the spectral/temporal degree of
freedom. We experimentally demonstrate a measurement of a full 4-dimensional
transverse-wavevector-spectral correlations between pairs of photons produced
in the non-collinear spontaneous parametric downconversion (SPDC). Utilization
of a custom ultra-fast single-photon camera provides high resolution and a
short measurement time.Comment: 7 pages, 3 figure
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