139 research outputs found
Size-independent Young's modulus of inverted conical GaAs nanowire resonators
We explore mechanical properties of top down fabricated, singly clamped
inverted conical GaAs nanowires. Combining nanowire lengths of 2-9 m with
foot diameters of 36-935 nm yields fundamental flexural eigenmodes spanning two
orders of magnitude from 200 kHz to 42 MHz. We extract a size-independent value
of Young's modulus of (453) GPa. With foot diameters down to a few tens of
nanometers, the investigated nanowires are promising candidates for
ultra-flexible and ultra-sensitive nanomechanical devices
Cavity-enhanced optical detection of carbon nanotube Brownian motion
Optical cavities with small mode volume are well-suited to detect the
vibration of sub-wavelength sized objects. Here we employ a fiber-based,
high-finesse optical microcavity to detect the Brownian motion of a freely
suspended carbon nanotube at room temperature under vacuum. The optical
detection resolves deflections of the oscillating tube down to 50pm/Hz^1/2. A
full vibrational spectrum of the carbon nanotube is obtained and confirmed by
characterization of the same device in a scanning electron microscope. Our work
successfully extends the principles of high-sensitivity optomechanical
detection to molecular scale nanomechanical systems.Comment: 14 pages, 11 figure
Shear-Induced Isotropic-to-Lamellar Transition in a Lattice-Gas Model of Ternary Amphiphilic Fluids
Although shear-induced isotropic-to-lamellar transitions in ternary systems
of oil, water and surfactant have been observed experimentally and predicted
theoretically by simple models for some time now, their numerical simulation
has not been achieved so far. In this work we demonstrate that a recently
introduced hydrodynamic lattice-gas model of amphiphilic fluids is well suited
for this purpose: the two-dimensional version of this model does indeed exhibit
a shear-induced isotropic-to-lamellar phase transition.Comment: 17 pages, LaTeX with epsf and REVTeX, PostScript and EPS
illustrations included. To appear in J. Phys. Cond. Ma
State tomography of capacitively shunted phase qubits with high fidelity
We introduce a new design concept for superconducting quantum bits (qubits)
in which we explicitly separate the capacitive element from the Josephson
tunnel junction for improved qubit performance. The number of two-level systems
(TLS) that couple to the qubit is thereby reduced by an order of magnitude and
the measurement fidelity improves to 90%. This improved design enables the
first demonstration of quantum state tomography with superconducting qubits
using single shot measurements.Comment: submitted to PR
Collective dynamics of strain-coupled nanomechanical pillar resonators
Semiconductur nano- and micropillars represent a promising platform for hybrid nanodevices. Their ability to couple to a broad variety of nanomechanical, acoustic, charge, spin, excitonic, polaritonic, or electromagnetic excitations is utilized in fields as diverse as force sensing or optoelectronics. In order to fully exploit the potential of these versatile systems e.g. for metamaterials, synchronization or topologically protected devices an intrinsic coupling mechanism between individual pillars needs to be established. This can be accomplished by taking advantage of the strain field induced by the flexural modes of the pillars. Here, we demonstrate strain-induced, strong coupling between two adjacent nanomechanical pillar resonators. Both mode hybridization and the formation of an avoided level crossing in the response of the nanopillar pair are experimentally observed. The described coupling mechanism is readily scalable, enabling hybrid nanomechanical resonator networks for the investigation of a broad range of collective dynamical phenomena
Microwave Dielectric Loss at Single Photon Energies and milliKelvin Temperatures
The microwave performance of amorphous dielectric materials at very low
temperatures and very low excitation strengths displays significant excess
loss. Here, we present the loss tangents of some common amorphous and
crystalline dielectrics, measured at low temperatures (T < 100 mK) with near
single-photon excitation energies, using both coplanar waveguide (CPW) and
lumped LC resonators. The loss can be understood using a two-level state (TLS)
defect model. A circuit analysis of the half-wavelength resonators we used is
outlined, and the energy dissipation of such a resonator on a multilayered
dielectric substrate is considered theoretically.Comment: 4 pages, 3 figures, submitted to Applied Physics Letter
Optomechanics for quantum technologies
The ability to control the motion of mechanical systems through interaction with light has opened the door to a plethora of applications in fundamental and applied physics. With experiments routinely reaching the quantum regime, the focus has now turned towards creating and exploiting interesting non-classical states of motion and entanglement in optomechanical systems. Quantumness has also shifted from being the very reason why experiments are constructed to becoming a resource for the investigation of fundamental physics and the creation of quantum technologies. Here, by focusing on opto- and electromechanical platforms we review recent progress in quantum state preparation and entanglement of mechanical systems, together with applications to signal processing and transduction, quantum sensing and topological physics, as well as small-scale thermodynamics
Measuring nanomechanical motion with an imprecision far below the standard quantum limit
We demonstrate a transducer of nanomechanical motion based on cavity enhanced
optical near-fields capable of achieving a shot-noise limited imprecision more
than 10 dB below the standard quantum limit (SQL). Residual background due to
fundamental thermodynamical frequency fluctuations allows a total imprecision 3
dB below the SQL at room temperature (corresponding to 600 am/Hz^(1/2) in
absolute units) and is known to reduce to negligible values for moderate
cryogenic temperatures. The transducer operates deeply in the quantum
backaction dominated regime, prerequisite for exploring quantum backaction,
measurement-induced squeezing and accessing sub-SQL sensitivity using
backaction evading techniques
Cooper-pair coherence in a superfluid Fermi-gas of atoms
We study the coherence properties of a trapped two-component gas of fermionic
atoms below the BCS critical temperature. We propose an optical method to
investigate the Cooper-pair coherence across different regions of the
superfluid. Near-resonant laser light is used to induce transitions between the
two coupled hyperfine states. The beam is split so that it probes two spatially
separate regions of the gas. Absorption of the light in this interferometric
scheme depends on the Cooper-pair coherence between the two regions.Comment: 10 pages, 5 figures. Submitted to J. Phys. B as a proceedings of the
Salerno 2001 BEC worksho
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