4,084 research outputs found
Enhancing quantum transduction via long-range waveguide mediated interactions between quantum emitters
Efficient transduction of electromagnetic signals between different frequency
scales is an essential ingredient for modern communication technologies as well
as for the emergent field of quantum information processing. Recent advances in
waveguide photonics have enabled a breakthrough in light-matter coupling, where
individual two-level emitters are strongly coupled to individual photons. Here
we propose a scheme which exploits this coupling to boost the performance of
transducers between low-frequency signals and optical fields operating at the
level of individual photons. Specifically, we demonstrate how to engineer the
interaction between quantum dots in waveguides to enable efficient transduction
of electric fields coupled to quantum dots. Owing to the scalability and
integrability of the solid-state platform, our transducer can potentially
become a key building block of a quantum internet node. To demonstrate this, we
show how it can be used as a coherent quantum interface between optical photons
and a two-level system like a superconducting qubit.Comment: The maintext has 6 pages, two column and 4 figure
Multi-partite entanglement detection with non symmetric probing
We show that spin squeezing criteria commonly used for entanglement detection
can be erroneous, if the probe is not symmetric. We then derive a lower bound
on squeezing for separable states in spin systems probed asymmetrically. Using
this we further develop a procedure that allows us to verify the degree of
entanglement of a quantum state in the spin system. Finally, we apply our
method for entanglement verification to existing experimental data, and use it
to prove the existence of tri-partite entanglement in a spin squeezed atomic
ensemble.Comment: 7 pages, 2 figures (Include Supplemental material
Photon Scattering from a System of Multi-Level Quantum Emitters. I. Formalism
We introduce a formalism to solve the problem of photon scattering from a
system of multi-level quantum emitters. Our approach provides a direct solution
of the scattering dynamics. As such the formalism gives the scattered fields
amplitudes in the limit of a weak incident intensity. Our formalism is equipped
to treat both multi-emitter and multi-level emitter systems, and is applicable
to a plethora of photon scattering problems including conditional state
preparation by photo-detection. In this paper, we develop the general formalism
for an arbitrary geometry. In the following paper (part II), we reduce the
general photon scattering formalism to a form that is applicable to
-dimensional waveguides, and show its applicability by considering explicit
examples with various emitter configurations.Comment: This is first part of a two part series of papers. It has 11 pages,
double column, and one figur
Photonic Controlled-Phase Gates Through Rydberg Blockade in Optical Cavities
We propose a novel scheme for high fidelity photonic controlled phase gates
using Rydberg blockade in an ensemble of atoms in an optical cavity. The gate
operation is obtained by first storing a photonic pulse in the ensemble and
then scattering a second pulse from the cavity, resulting in a phase change
depending on whether the first pulse contained a single photon. We show that
the combination of Rydberg blockade and optical cavities effectively enhances
the optical non-linearity created by the strong Rydberg interaction and thereby
reduces the requirements for photonic quantum gates. The resulting gate can be
implemented with cavities of moderate finesse which allows for highly efficient
processing of quantum information encoded in photons. As a particular example
of this, we show how the gate can be employed to increase the communication
rate of quantum repeaters based on atomic ensembles.Comment: main manuscript 5 pages with 11 pages of supplementary informatio
Violation of Bell's inequality with quantum-dot single-photon sources
We investigate the possibility of realizing a loophole-free violation of
Bell's inequality using deterministic single-photon sources. We provide a
detailed analysis of a scheme to achieve such violations over long distances
with immediate extensions to device-independent quantum key distribution. We
investigate the effect of key experimental imperfections that are unavoidable
in real-world single-photon sources including the finite degree of photon
indistinguishability, single-photon purity, and the overall source efficiency.
We benchmark the performance requirements to state-of-the-art deterministic
single-photon sources based on quantum dots in photonic nanostructures and find
that experimental realizations appear to be within reach. We also evaluate the
requirements for a post-selected version of the protocol, which relaxes the
demanding requirements with respect to the source efficiency.Comment: 17 pages, 8 figure
A device for extraction, manipulation and stretching of DNA from single human chromosomes
We describe the structure and operation of a micro/nanofluidic device in which individual metaphase chromosomes can be isolated and processed without being displaced during exchange of reagents. The change in chromosome morphology as a result of introducing protease into the device was observed by time-lapse imaging; pressure-driven flow was then used to shunt the chromosomal DNA package into a nanoslit. A long linear DNA strand (>1.3 Mbp) was seen to stretch out from the DNA package and along the length of the nanoslit. Delivery of DNA in its native metaphase chromosome package as well as the microfluidic environment prevented DNA from shearing and will be important for preparing ultra-long lengths of DNA for nanofluidic analysis
Characterisation of the horse transcriptome from immunologically active tissues
The immune system of the horse has not been well studied, despite the fact that the horse displays several features such as sensitivity to bacterial lipopolysaccharide that make them in many ways a more suitable model of some human disorders than the current rodent models. The difficulty of working with large animal models has however limited characterisation of gene expression in the horse immune system with current annotations for the equine genome restricted to predictions from other mammals and the few described horse proteins. This paper outlines sequencing of 184 million transcriptome short reads from immunologically active tissues of three horses including the genome reference “Twilight”. In a comparison with the Ensembl horse genome annotation, we found 8,763 potentially novel isoforms
Comparison of an approximately isothermal gravitational potentials of elliptical galaxies based on X-ray and optical data
We analyze six X-ray bright elliptical galaxies, observed with Chandra and
XMM-Newton, and approximate their gravitational potentials by isothermal
spheres phi(r)=v_c^2 ln(r) over a range of radii from ~0.5 to ~25 kpc. We then
compare the circular speed v_c derived from X-ray data with the estimators
available from optical data. In particular we discuss two simple and robust
procedures for evaluating the circular speed of the galaxy using the observed
optical surface brightness and the line-of-sight velocity dispersion profiles.
The best fitting relation between the circular speeds derived from optical
observations of stars and X-ray observations of hot gas is v_{c,opt}~ \eta *
v_{c,X}, where \eta=1.10-1.15 (depending on the method), suggesting, albeit
with large statistical and systematic uncertainties, that non-thermal pressure
on average contributes ~20-30% of the gas thermal pressure.Comment: 24 pages, 15 figures; Accepted for publication in MNRA
- …