1,198 research outputs found
Generation of mechanical interference fringes by multi-photon counting
Exploring the quantum behaviour of macroscopic objects provides an intriguing
avenue to study the foundations of physics and to develop a suite of
quantum-enhanced technologies. One prominent path of study is provided by
quantum optomechanics which utilizes the tools of quantum optics to control the
motion of macroscopic mechanical resonators. Despite excellent recent progress,
the preparation of mechanical quantum superposition states remains outstanding
due to weak coupling and thermal decoherence. Here we present a novel
optomechanical scheme that significantly relaxes these requirements allowing
the preparation of quantum superposition states of motion of a mechanical
resonator by exploiting the nonlinearity of multi-photon quantum measurements.
Our method is capable of generating non-classical mechanical states without the
need for strong single photon coupling, is resilient against optical loss, and
offers more favourable scaling against initial mechanical thermal occupation
than existing schemes. Moreover, our approach allows the generation of larger
superposition states by projecting the optical field onto NOON states. We
experimentally demonstrate this multi-photon-counting technique on a mechanical
thermal state in the classical limit and observe interference fringes in the
mechanical position distribution that show phase superresolution. This opens a
feasible route to explore and exploit quantum phenomena at a macroscopic scale.Comment: 16 pages, 4 figures. v1: submitted for review on 28 Jan 2016. v2:
significantly revised manuscript. v3: some further revisions and some extra
results included. v3: new results added, extra author added, close to
published version, supplementary material available with published versio
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
On The Phase Structure and Thermodynamic Geometry of R-Charged Black Holes
We study the phase structure and equilibrium state space geometry of
R-charged black holes in , 4 and 7 and the corresponding rotating ,
and branes. For various charge configurations of the compact black
holes in the canonical ensemble we demonstrate new liquid-gas like phase
coexistence behaviour culminating in second order critical points. The critical
exponents turn out to be the same as that of four dimensional asymptotically
AdS black holes in Einstein Maxwell theory. We further establish that the
regions of stability for R-charged black holes are, in some cases, more
constrained than is currently believed, due to properties of some of the
response coefficients. The equilibrium state space scalar curvature is
calculated for various charge configurations, both for the case of compact as
well as flat horizons and its asymptotic behaviour with temperature is
established.Comment: 1 + 33 pages, LaTeX, 25 figures. References adde
On the Thermodynamic Geometry and Critical Phenomena of AdS Black Holes
In this paper, we study various aspects of the equilibrium thermodynamic
state space geometry of AdS black holes. We first examine the
Reissner-Nordstrom-AdS (RN-AdS) and the Kerr-AdS black holes. In this context,
the state space scalar curvature of these black holes is analysed in various
regions of their thermodynamic parameter space. This provides important new
insights into the structure and significance of the scalar curvature. We
further investigate critical phenomena, and the behaviour of the scalar
curvature near criticality, for KN-AdS black holes in two mixed ensembles,
introduced and elucidated in our earlier work arXiv:1002.2538 [hep-th]. The
critical exponents are identical to those in the RN-AdS and Kerr-AdS cases in
the canonical ensemble. This suggests an universality in the scaling behaviour
near critical points of AdS black holes. Our results further highlight
qualitative differences in the thermodynamic state space geometry for electric
charge and angular momentum fluctuations of these.Comment: 1 + 37 Pages, LaTeX, includes 31 figures. A figure and a
clarification added
Kerr-Newman Black Hole Thermodynamical State Space: Blockwise Coordinates
A coordinate system that blockwise-simplifies the Kerr-Newman black hole's
thermodynamical state space Ruppeiner metric geometry is constructed, with
discussion of the limiting cases corresponding to simpler black holes. It is
deduced that one of the three conformal Killing vectors of the
Reissner-Nordstrom and Kerr cases (whose thermodynamical state space metrics
are 2 by 2 and conformally flat) survives generalization to the Kerr-Newman
case's 3 by 3 thermodynamical state space metric.Comment: 4 pages incl 2 figs. Accepted by Gen. Rel. Grav. Replaced with
Accepted version (minor corrections
Seasonal and diurnal variations of particulate nitrate and organic matter at the IfT research station Melpitz
Ammonium nitrate and several organic compounds such as dicarboxylic acids (e.g. succinic acid, glutaric acid), some Polycyclic Aromatic Hydrocarbon (PAHs) or some n-alkanes are semi-volatile. The transition of these compounds between the gas and particulate phase may significantly change the aerosol particles radiative properties, the heterogeneous chemical properties, and, naturally, the total particulate mass concentration. To better assess these time-dependent effects, three intensive field experiments were conducted in 2008â2009 at the Central European EMEP research station Melpitz (Germany) using an Aerodyne Aerosol Mass Spectrometer (AMS). Data from all seasons highlight organic matter as being the most important particulate fraction of PM1 in summer (59%) while in winter, the nitrate fraction was more prevalent (34.4%). The diurnal variation of nitrate always showed the lowest concentration during the day while its concentration increased during the night. This night increase of nitrate concentration was higher in winter (ÎNO3â = 3.6 ÎŒg mâ3) than in summer (ÎNO3â = 0.7 ÎŒg mâ3). The variation in particulate nitrate was inherently linked to the gas-to-particle-phase equilibrium of ammonium nitrate and the dynamics of the atmosphere during day. The results of this study suggest that during summer nights, the condensation of HNO3 and NH3 on pre-existing particles represents the most prevalent source of nitrate, whereas during winter, nighttime chemistry is the predominant source of nitrate. During the summer 2008's campaign, a clear diurnal evolution in the oxidation state of the organic matter became evident (Organic Mass to Organic Carbon ratio (OM/OC) ranging from 1.65 during night to 1.80 during day and carbon oxidation state (OSc) from â0.66 to â0.4), which could be correlated to hydroxyl radical (OH) and ozone concentrations, indicating a photochemical transformation process. In summer, the organic particulate matter seemed to be heavily influenced by regional secondary formation and transformation processes, facilitated by photochemical production processes as well as a diurnal cycling of the substances between the gas and particulate phase. In winter, these processes were obviously less pronounced (OM/OC ranging from 1.60 to 1.67 and OSc from â0.8 to â0.7), so that organic matter apparently originated mainly from aged particles and long range transport
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
- âŠ