1,039 research outputs found
Manipulating biphotonic qutrits
Quantum information carriers with higher dimension than the canonical qubit
offer significant advantages. However, manipulating such systems is extremely
difficult. We show how measurement induced non-linearities can be employed to
dramatically extend the range of possible transforms on biphotonic qutrits; the
three level quantum systems formed by the polarisation of two photons in the
same spatio-temporal mode. We fully characterise the biphoton-photon
entanglement that underpins our technique, thereby realising the first instance
of qubit-qutrit entanglement. We discuss an extension of our technique to
generate qutrit-qutrit entanglement and to manipulate any bosonic encoding of
quantum information.Comment: 4 pages, 4 figure
Demonstration of a simple entangling optical gate and its use in Bell-state analysis
We demonstrate a new architecture for an optical entangling gate that is
significantly simpler than previous realisations, using partially-polarising
beamsplitters so that only a single optical mode-matching condition is
required. We demonstrate operation of a controlled-Z gate in both
continuous-wave and pulsed regimes of operation, fully characterising it in
each case using quantum process tomography. We also demonstrate a
fully-resolving, nondeterministic optical Bell-state analyser based on this
controlled-Z gate. This new architecture is ideally suited to guided optics
implementations of optical gates.Comment: 4 pages, 3 figures. v2: additional author, improved data and figures
(low res), some other minor changes. Accepted for publication in PR
Experimental demonstration of Shor's algorithm with quantum entanglement
Shor's powerful quantum algorithm for factoring represents a major challenge
in quantum computation and its full realization will have a large impact on
modern cryptography. Here we implement a compiled version of Shor's algorithm
in a photonic system using single photons and employing the non-linearity
induced by measurement. For the first time we demonstrate the core processes,
coherent control, and resultant entangled states that are required in a
full-scale implementation of Shor's algorithm. Demonstration of these processes
is a necessary step on the path towards a full implementation of Shor's
algorithm and scalable quantum computing. Our results highlight that the
performance of a quantum algorithm is not the same as performance of the
underlying quantum circuit, and stress the importance of developing techniques
for characterising quantum algorithms.Comment: 4 pages, 5 figures + half-page additional online materia
Entanglement generation by Fock-state filtration
We demonstrate a Fock-state filter which is capable of preferentially
blocking single photons over photon pairs. The large conditional nonlinearities
are based on higher-order quantum interference, using linear optics, an ancilla
photon, and measurement. We demonstrate that the filter acts coherently by
using it to convert unentangled photon pairs to a path-entangled state. We
quantify the degree of entanglement by transforming the path information to
polarisation information, applying quantum state tomography we measure a tangle
of T=(20+/-9)%.Comment: 4 pages, 3 figure
Optogalvanic Spectroscopy of Metastable States in Yb^{+}
The metastable ^{2}F_{7/2} and ^{2}D_{3/2} states of Yb^{+} are of interest
for applications in metrology and quantum information and also act as dark
states in laser cooling. These metastable states are commonly repumped to the
ground state via the 638.6 nm ^{2}F_{7/2} -- ^{1}D[5/2]_{5/2} and 935.2 nm
^{2}D_{3/2} -- ^{3}D[3/2]_{1/2} transitions. We have performed optogalvanic
spectroscopy of these transitions in Yb^{+} ions generated in a discharge. We
measure the pressure broadening coefficient for the 638.6 nm transition to be
70 \pm 10 MHz mbar^{-1}. We place an upper bound of 375 MHz/nucleon on the
638.6 nm isotope splitting and show that our observations are consistent with
theory for the hyperfine splitting. Our measurements of the 935.2 nm transition
extend those made by Sugiyama et al, showing well-resolved isotope and
hyperfine splitting. We obtain high signal to noise, sufficient for laser
stabilisation applications.Comment: 8 pages, 5 figure
Dynamics of Resonances in Strongly Interacting Systems
The effects of the propagation of particles which have a finite life-time and
an according broad distribution in their mass spectrum are discussed in the
context of a transport descriptions. In the first part some example cases of
mesonic modes in nuclear matter at finite densities and temperatures are
presented. These equilibrium calculations illustrate the dynamical range of
spectral distributions to be adequately covered by non-equilibrium description
of the dynamics of two nuclei colliding at high energies. The second part
addresses the problem of transport descriptions which properly account for the
damping width of the particles. A systematic and general gradient approximation
is presented in the form of diagrammatic rules which permit to derive a
self-consistent transport scheme from the Kadanoff--Baym equation. The scheme
is conserving and thermodynamically consistent provided the self-energies are
obtained within the Phi-derivable two-particle irreducible (2PI) method of
Baym. The merits, the limitations and partial cures of the limitations of this
transport scheme are discussed in detail.Comment: To appear in the proceedings of the International Conference
"Progress in Nonequilibrium Green's Functions III", Kiel, 22.-26. August 200
2-Aminopurine flipped into the active site of the adenine-specific DNA methyltransferase M.Taql: Crystal structures and time-resolved fluorescence
Age-related decline in protein synthesis in the rat parotid gland
This study was undertaken to determine whether protein synthesis declines with age in parorid salivary glands. We have examined the level of incorporation of [3H]-leucine into protein and the metabolism of [U-14C]-D-glucose in 2-, 12-, 18-, 24- and 30-month-old rats. The rate of incorporation of [3H]-leucine into perchloric acid insoluble protein by gland slices decreases progressively with age from 138.43+/-5.43 nmole/mg DNA/h at 2 months to 109.77+/-6.88, 97+/-4.68, 71.62+/-4.13 and 58.08+/-5.61 nmole/mg DNA/h at 12, 18, 24 and 30 months, respectively. The amount of radioactivity in the perchloric acid soluble fraction remains relatively stable at all ages. The ability of gland slices to oxidize [U-14C]-D-glucose to 14CO2 and to incorporate radioactivity into the total lipid does not change with age, whereas the incorporation of radioactivity into protein decreases significantly from 45.06+/-3.55 at 2 months to 21.75+/-1.30 nmoles glucuse/mg DNA/h at 24 months. Histologically, no significant change is detected in the proportion of secretory cells to ductal cells in the different age groups. In radioautographs of the glands incubated with [3H]-leucine, the distribution of cells with grains is similar in all age groups. Lipid droplets occur at the periphery of the lobules and a large number of lipofuscin granules are present in secretory acinar cells of 12-month-old and older rats when viewed in the electron microscope. However, the structural integrity in the cellular organelles is maintained in the acinar cells of all age groups. These results indicate that the ability of parotid gland cells to synthesize protein decreases with age. The decrease reflects specific changes in protein synthesis and not an overall decline in cellular metabolism or a decrease in the number of cells which incorporate leucine.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/23360/1/0000304.pd
An Exact Fluctuating 1/2-BPS Configuration
This work explores the role of thermodynamic fluctuations in the two
parameter giant and superstar configurations characterized by an ensemble of
arbitrary liquid droplets or irregular shaped fuzzballs. Our analysis
illustrates that the chemical and state-space geometric descriptions exhibit an
intriguing set of exact pair correction functions and the global correlation
lengths. The first principle of statistical mechanics shows that the possible
canonical fluctuations may precisely be ascertained without any approximation.
Interestingly, our intrinsic geometric study exemplifies that there exist exact
fluctuating 1/2-BPS statistical configurations which involve an ensemble of
microstates describing the liquid droplets or fuzzballs. The Gaussian
fluctuations over an equilibrium chemical and state-space configurations
accomplish a well-defined, non-degenerate, curved and regular intrinsic
Riemannian manifolds for all physically admissible domains of black hole
parameters. An explicit computation demonstrates that the underlying chemical
correlations involve ordinary summations, whilst the state-space correlations
may simply be depicted by standard polygamma functions. Our construction
ascribes definite stability character to the canonical energy fluctuations and
to the counting entropy associated with an arbitrary choice of excited boxes
from an ensemble of ample boxes constituting a variety of Young tableaux.Comment: Minor changes, added references, 30 pages, 4 figures, PACS numbers:
04.70.-s: Physics of black holes; 04.70.-Bw: Classical black holes; 04.50.Gh
Higher-dimensional black holes, black strings, and related objects; 04.60.Cf
Gravitational aspects of string theory, accepted for publication in JHE
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