89,778 research outputs found
Optomechanical state reconstruction and nonclassicality verification beyond the resolved-sideband regime
Quantum optomechanics uses optical means to generate and manipulate quantum
states of motion of mechanical resonators. This provides an intriguing platform
for the study of fundamental physics and the development of novel quantum
devices. Yet, the challenge of reconstructing and verifying the quantum state
of mechanical systems has remained a major roadblock in the field. Here, we
present a novel approach that allows for tomographic reconstruction of the
quantum state of a mechanical system without the need for extremely high
quality optical cavities. We show that, without relying on the usual state
transfer presumption between light an mechanics, the full optomechanical
Hamiltonian can be exploited to imprint mechanical tomograms on a strong
optical coherent pulse, which can then be read out using well-established
techniques. Furthermore, with only a small number of measurements, our method
can be used to witness nonclassical features of mechanical systems without
requiring full tomography. By relaxing the experimental requirements, our
technique thus opens a feasible route towards verifying the quantum state of
mechanical resonators and their nonclassical behaviour in a wide range of
optomechanical systems.Comment: 12 pages + 9 pages of appendices, 4 figure
Reactor monitoring and safeguards using antineutrino detectors
Nuclear reactors have served as the antineutrino source for many fundamental
physics experiments. The techniques developed by these experiments make it
possible to use these very weakly interacting particles for a practical
purpose. The large flux of antineutrinos that leaves a reactor carries
information about two quantities of interest for safeguards: the reactor power
and fissile inventory. Measurements made with antineutrino detectors could
therefore offer an alternative means for verifying the power history and
fissile inventory of a reactors, as part of International Atomic Energy Agency
(IAEA) and other reactor safeguards regimes. Several efforts to develop this
monitoring technique are underway across the globe.Comment: 6 pages, 4 figures, Proceedings of XXIII International Conference on
Neutrino Physics and Astrophysics (Neutrino 2008); v2: minor additions to
reference
Sub-Millisecond Measurements of Thermal Conductivity and Thermal Diffusivity Using Micrometer-Sized Hot Strips
A new measurement technique based on the transient hot strip technique has recently been developed for studying anisotropic thermal transport properties of thin crystalline films. A micrometer-sized hot strip sensor is evaporated on the surface of the crystalline film sample, which has been deposited on a substrate wafer of limited thickness. From a pulsed transient recording, using sub-millisecond square-shaped pulses, a thermal probing depth that is less than the film thickness is assured. In the ongoing work of verifying the technique, we show results from measurements on z-cut crystal quartz and fused silica, using thermal probing depths of only 30 μm, which closely conform to bulk values found in the literature
Quantum teleportation between light and matter
Quantum teleportation is an important ingredient in distributed quantum
networks, and can also serve as an elementary operation in quantum computers.
Teleportation was first demonstrated as a transfer of a quantum state of light
onto another light beam; later developments used optical relays and
demonstrated entanglement swapping for continuous variables. The teleportation
of a quantum state between two single material particles (trapped ions) has now
also been achieved. Here we demonstrate teleportation between objects of a
different nature - light and matter, which respectively represent 'flying' and
'stationary' media. A quantum state encoded in a light pulse is teleported onto
a macroscopic object (an atomic ensemble containing 10^12 caesium atoms).
Deterministic teleportation is achieved for sets of coherent states with mean
photon number (n) up to a few hundred. The fidelities are 0.58+-0.02 for n=20
and 0.60+-0.02 for n=5 - higher than any classical state transfer can possibly
achieve. Besides being of fundamental interest, teleportation using a
macroscopic atomic ensemble is relevant for the practical implementation of a
quantum repeater. An important factor for the implementation of quantum
networks is the teleportation distance between transmitter and receiver; this
is 0.5 metres in the present experiment. As our experiment uses propagating
light to achieve the entanglement of light and atoms required for
teleportation, the present approach should be scalable to longer distances.Comment: 23 pages, 8 figures, incl. supplementary informatio
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