2,588 research outputs found
Engineering asymmetric steady-state Einstein-Podolsky-Rosen steering in macroscopic hybrid systems
Generation of quantum correlations between separate objects is of
significance both in fundamental physics and in quantum networks. One important
challenge is to create the directional "spooky action-at-a-distanc" effects
that Schr\"{o}dinger called "steering" between two macroscopic and massive
objects. Here, we analyze a generic scheme for generating steering correlations
in cascaded hybrid systems in which two distant oscillators with effective
masses of opposite signs are coupled to a unidirectional light field, a setup
which is known to build up quantum correlations by means of quantum back-action
evasion. The unidirectional coupling of the first to the second oscillator via
the light field can be engineered to enhance steering in both directions and
provides an active method for controlling the asymmetry of steering. We show
that the resulting scheme can efficiently generate unconditional steady-state
Einstein-Podolsky-Rosen steering between the two subsystems, even in the
presence of thermal noise and optical losses. As a scenario of particular
technological interest in quantum networks, we use our scheme to engineer
enhanced steering from an untrusted node with limited tunability (in terms of
interaction strength and type with the light field) to a trusted, highly
tunable node, hence offering a path to implementing one-sided
device-independent quantum tasks.Comment: 11 pages, 8 figure
Electro-optomechanical equivalent circuits for quantum transduction
Using the techniques of optomechanics, a high- mechanical oscillator may
serve as a link between electromagnetic modes of vastly different frequencies.
This approach has successfully been exploited for the frequency conversion of
classical signals and has the potential of performing quantum state transfer
between superconducting circuitry and a traveling optical signal. Such
transducers are often operated in a linear regime, where the hybrid system can
be described using linear response theory based on the Heisenberg-Langevin
equations. While mathematically straightforward to solve, this approach yields
little intuition about the dynamics of the hybrid system to aid the
optimization of the transducer. As an analysis and design tool for such
electro-optomechanical transducers, we introduce an equivalent circuit
formalism, where the entire transducer is represented by an electrical circuit.
Thereby we integrate the transduction functionality of optomechanical systems
into the toolbox of electrical engineering allowing the use of its
well-established design techniques. This unifying impedance description can be
applied both for static (DC) and harmonically varying (AC) drive fields,
accommodates arbitrary linear circuits, and is not restricted to the
resolved-sideband regime. Furthermore, by establishing the quantized
input-output formalism for the equivalent circuit, we obtain the scattering
matrix for linear transducers using circuit analysis, and thereby have a
complete quantum mechanical characterization of the transducer. Hence, this
mapping of the entire transducer to the language of electrical engineering both
sheds light on how the transducer performs and can at the same time be used to
optimize its performance by aiding the design of a suitable electrical circuit.Comment: 30 pages, 9 figure
Osmotic Water Transport with Glucose in GLUT2 and SGLT
Carrier-mediated water cotransport is currently a favored explanation for water movement against an osmotic gradient. The vestibule within the central pore of Na+-dependent cotransporters or GLUT2 provides the necessary precondition for an osmotic mechanism, explaining this phenomenon without carriers. Simulating equilibrative glucose inflow via the narrow external orifice of GLUT2 raises vestibular tonicity relative to the external solution. Vestibular hypertonicity causes osmotic water inflow, which raises vestibular hydrostatic pressure and forces water, salt, and glucose into the outer cytosolic layer via its wide endofacial exit. Glucose uptake via GLUT2 also raises oocyte tonicity. Glucose exit from preloaded cells depletes the vestibule of glucose, making it hypotonic and thereby inducing water efflux. Inhibiting glucose exit with phloretin reestablishes vestibular hypertonicity, as it reequilibrates with the cytosolic glucose and net water inflow recommences. Simulated Na+-glucose cotransport demonstrates that active glucose accumulation within the vestibule generates water flows simultaneously with the onset of glucose flow and before any flow external to the transporter caused by hypertonicity in the outer cytosolic layers. The molar ratio of water/glucose flow is seen now to relate to the ratio of hydraulic and glucose permeability rather than to water storage capacity of putative water carriers
Correlated photon dynamics in dissipative Rydberg media
Rydberg blockade physics in optically dense atomic media under the conditions
of electromagnetically induced transparency (EIT) leads to strong dissipative
interactions between single photons. We introduce a new approach to analyzing
this challenging many-body problem in the limit of large optical depth per
blockade radius. In our approach, we separate the single-polariton EIT physics
from Rydberg-Rydberg interactions in a serialized manner while using a
hard-sphere model for the latter, thus capturing the dualistic particle-wave
nature of light as it manifests itself in dissipative Rydberg-EIT media. Using
this approach, we analyze the saturation behavior of the transmission through
one-dimensional Rydberg-EIT media in the regime of non-perturbative dissipative
interactions relevant to current experiments. Our model is able to capture the
many-body dynamics of bright, coherent pulses through these strongly
interacting media. We compare our model with available experimental data in
this regime and find good agreement. We also analyze a scheme for generating
regular trains of single photons from continuous-wave input and derive its
scaling behavior in the presence of imperfect single-photon EIT.Comment: Final version. 6 pages, 4 figures (+ Supplemental Material; 7 pages,
3 figures
Biofuels in the transition of Maersk
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Dynamic Computational Workload-Based Co-Processing
A computing device may dynamically determine a strong coprocessor to perform peerto-peer updates. The computing device may advertise its hardware capabilities as services to enable co-processing and peer-to-peer updates. Based on the information provided by other devices in the local network, the computing device may automatically send work to some devices with more processing capabilities. The computing device may be configured to automatically offload computation from less powerful devices (e.g., mobile phones) to other more powerful devices (e.g., personal computers) in a local network. The computing device may also receive at least a portion of one or more files from other devices from the local network and share at least a portion of one or more files to other devices in the local network. A dedicated computing device or a super node may be used to download auto-updates and perform peer-topeer auto-updates
Unconditional steady-state entanglement in macroscopic hybrid systems by coherent noise cancellation
The generation of entanglement between disparate physical objects is a key
ingredient in the field of quantum technologies, since they can have different
functionalities in a quantum network. Here we propose and analyze a generic
approach to steady-state entanglement generation between two oscillators with
different temperatures and decoherence properties coupled in cascade to a
common unidirectional light field. The scheme is based on a combination of
coherent noise cancellation and dynamical cooling techniques for two
oscillators with effective masses of opposite signs, such as quasi-spin and
motional degrees of freedom, respectively. The interference effect provided by
the cascaded setup can be tuned to implement additional noise cancellation
leading to improved entanglement even in the presence of a hot thermal
environment. The unconditional entanglement generation is advantageous since it
provides a ready-to-use quantum resource. Remarkably, by comparing to the
conditional entanglement achievable in the dynamically stable regime, we find
our unconditional scheme to deliver a virtually identical performance when
operated optimally.Comment: Final version; 6 pages, 3 figures + Supplemental Materia
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