449 research outputs found
Fracture strength and Young's modulus of ZnO nanowires
The fracture strength of ZnO nanowires vertically grown on sapphire
substrates was measured in tensile and bending experiments. Nanowires with
diameters between 60 and 310 nm and a typical length of 2 um were manipulated
with an atomic force microscopy tip mounted on a nanomanipulator inside a
scanning electron microscope. The fracture strain of (7.7 +- 0.8)% measured in
the bending test was found close to the theoretical limit of 10% and revealed a
strength about twice as high as in the tensile test. From the tensile
experiments the Young's modulus could be measured to be within 30% of that of
bulk ZnO, contrary to the lower values found in literature.Comment: 5 pages, 3 figures, 1 tabl
Classical and quantum communication without a shared reference frame
We show that communication without a shared reference frame is possible using
entangled states. Both classical and quantum information can be communicated
with perfect fidelity without a shared reference frame at a rate that
asymptotically approaches one classical bit or one encoded qubit per
transmitted qubit. We present an optical scheme to communicate classical bits
without a shared reference frame using entangled photon pairs and linear
optical Bell state measurements.Comment: 4 pages, published versio
Optically controlled spin-glasses in multi-qubit cavity systems
Recent advances in nanostructure fabrication and optical control, suggest
that it will soon be possible to prepare collections of interacting two-level
systems (i.e. qubits) within an optical cavity. Here we show theoretically that
such systems could exhibit novel phase transition phenomena involving
spin-glass phases. By contrast with traditional realizations using magnetic
solids, these phase transition phenomena are associated with both matter and
radiation subsystems. Moreover the various phase transitions should be tunable
simply by varying the matter-radiation coupling strength.Comment: 4 pages, 3 figure
Quantum-dot single-photon sources for entanglement enhanced interferometry
The authors acknowledge financial support from the Center for Integrated Quantum Science and Technology (IQST).Multiphoton entangled states such as “N00N states” have attracted a lot of attention because of their possible application in high-precision, quantum enhanced phase determination. So far, N00N states have been generated in spontaneous parametric down-conversion processes and by mixing quantum and classical light on a beam splitter. Here, in contrast, we demonstrate superresolving phase measurements based on two-photon N00N states generated by quantum dot single-photon sources making use of the Hong-Ou-Mandel effect on a beam splitter. By means of pulsed resonance fluorescence of a charged exciton state, we achieve, in postselection, a quantum enhanced improvement of the precision in phase uncertainty, higher than prescribed by the standard quantum limit. An analytical description of the measurement scheme is provided, reflecting requirements, capability, and restraints of single-photon emitters in optical quantum metrology. Our results point toward the realization of a real-world quantum sensor in the near future.PostprintPostprintPeer reviewe
Quantum-dot single-photon sources for entanglement enhanced interferometry
The authors acknowledge financial support from the Center for Integrated Quantum Science and Technology (IQST).Multiphoton entangled states such as “N00N states” have attracted a lot of attention because of their possible application in high-precision, quantum enhanced phase determination. So far, N00N states have been generated in spontaneous parametric down-conversion processes and by mixing quantum and classical light on a beam splitter. Here, in contrast, we demonstrate superresolving phase measurements based on two-photon N00N states generated by quantum dot single-photon sources making use of the Hong-Ou-Mandel effect on a beam splitter. By means of pulsed resonance fluorescence of a charged exciton state, we achieve, in postselection, a quantum enhanced improvement of the precision in phase uncertainty, higher than prescribed by the standard quantum limit. An analytical description of the measurement scheme is provided, reflecting requirements, capability, and restraints of single-photon emitters in optical quantum metrology. Our results point toward the realization of a real-world quantum sensor in the near future.PostprintPostprintPeer reviewe
Linear optics implementation of general two-photon projective measurement
We will present a method of implementation of general projective measurement
of two-photon polarization state with the use of linear optics elements only.
The scheme presented succeeds with a probability of at least 1/16. For some
specific measurements, (e.g. parity measurement) this probability reaches 1/4.Comment: 8 page
Probabilistic Quantum Logic Operations Using Polarizing Beam Splitters
It has previously been shown that probabilistic quantum logic operations can
be performed using linear optical elements, additional photons (ancilla), and
post-selection based on the output of single-photon detectors. Here we describe
the operation of several quantum logic operations of an elementary nature,
including a quantum parity check and a quantum encoder, and we show how they
can be combined to implement a controlled-NOT (CNOT) gate. All of these gates
can be constructed using polarizing beam splitters that completely transmit one
state of polarization and totally reflect the orthogonal state of polarization,
which allows a simple explanation of each operation. We also describe a
polarizing beam splitter implementation of a CNOT gate that is closely
analogous to the quantum teleportation technique previously suggested by
Gottesman and Chuang [Nature 402, p.390 (1999)]. Finally, our approach has the
interesting feature that it makes practical use of a quantum-eraser technique.Comment: 9 pages, RevTex; Submitted to Phys. Rev. A; additional references
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