1,164 research outputs found
Mechanical On-Chip Microwave Circulator
Nonreciprocal circuit elements form an integral part of modern measurement
and communication systems. Mathematically they require breaking of
time-reversal symmetry, typically achieved using magnetic materials and more
recently using the quantum Hall effect, parametric permittivity modulation or
Josephson nonlinearities. Here, we demonstrate an on-chip magnetic-free
circulator based on reservoir engineered optomechanical interactions.
Directional circulation is achieved with controlled phase-sensitive
interference of six distinct electro-mechanical signal conversion paths. The
presented circulator is compact, its silicon-on-insulator platform is
compatible with both superconducting qubits and silicon photonics, and its
noise performance is close to the quantum limit. With a high dynamic range, a
tunable bandwidth of up to 30 MHz and an in-situ reconfigurability as beam
splitter or wavelength converter, it could pave the way for superconducting
qubit processors with integrated and multiplexed on-chip signal processing and
readout.Comment: References have been update
Stationary Entangled Radiation from Micromechanical Motion
Mechanical systems facilitate the development of a new generation of hybrid
quantum technology comprising electrical, optical, atomic and acoustic degrees
of freedom. Entanglement is the essential resource that defines this new
paradigm of quantum enabled devices. Continuous variable (CV) entangled fields,
known as Einstein-Podolsky-Rosen (EPR) states, are spatially separated two-mode
squeezed states that can be used to implement quantum teleportation and quantum
communication. In the optical domain, EPR states are typically generated using
nondegenerate optical amplifiers and at microwave frequencies Josephson
circuits can serve as a nonlinear medium. It is an outstanding goal to
deterministically generate and distribute entangled states with a mechanical
oscillator. Here we observe stationary emission of path-entangled microwave
radiation from a parametrically driven 30 micrometer long silicon nanostring
oscillator, squeezing the joint field operators of two thermal modes by
3.40(37) dB below the vacuum level. This mechanical system correlates up to 50
photons/s/Hz giving rise to a quantum discord that is robust with respect to
microwave noise. Such generalized quantum correlations of separable states are
important for quantum enhanced detection and provide direct evidence for the
non-classical nature of the mechanical oscillator without directly measuring
its state. This noninvasive measurement scheme allows to infer information
about otherwise inaccessible objects with potential implications in sensing,
open system dynamics and fundamental tests of quantum gravity. In the near
future, similar on-chip devices can be used to entangle subsystems on vastly
different energy scales such as microwave and optical photons.Comment: 13 pages, 5 figure
Novel Collective Effects in Integrated Photonics
Superradiance, the enhanced collective emission of energy from a coherent
ensemble of quantum systems, has been typically studied in atomic ensembles. In
this work we study theoretically the enhanced emission of energy from coherent
ensembles of harmonic oscillators. We show that it should be possible to
observe harmonic oscillator superradiance for the first time in waveguide
arrays in integrated photonics. Furthermore, we describe how pairwise
correlations within the ensemble can be measured with this architecture. These
pairwise correlations are an integral part of the phenomenon of superradiance
and have never been observed in experiments to date.Comment: 7 pages, 3 figure
Resposta de cultivares de trigo à infestação do pulgão Rhopalosiphum padi.
O objetivo deste trabalho foi avaliar a resposta de oito cultivares comerciais de trigo (BRS 194, BRS 208, BRS Camboatá, BRS Guabiju, BRS Guamirim, BRS Louro, BRS Timbaúva e BRS Umbu) à infestação do pulgão Rhopalosiphum padi (Hemiptera: Aphididae). O experimento foi realizado na Embrapa Trigo, em telado, em blocos ao acaso, com oito tratamentos e seis repetições, dispostos em parcelas subdivididas. As parcelas principais receberam os tratamentos com e sem infestação de pulgões, e as subparcelas foram compostas pelas cultivares. A infestação com os pulgões (20 adultos ápteros por planta) foi realizada aos 12 dias após a emergência das plantas, quando se encontravam no início do afilhamento, e foi mantida durante 15 dias. As cultivares avaliadas responderam diferentemente à infestação do pulgão R. padi. A cultivar BRS Timbaúva é a mais resistente, e as cultivares BRS Umbu e BRS Guabiju são as mais suscetíveis ao pulgão, quanto ao crescimento e a capacidade produtiva de plantas
Integrated Photonic Sensing
Loss is a critical roadblock to achieving photonic quantum-enhanced
technologies. We explore a modular platform for implementing integrated
photonics experiments and consider the effects of loss at different stages of
these experiments, including state preparation, manipulation and measurement.
We frame our discussion mainly in the context of quantum sensing and focus
particularly on the use of loss-tolerant Holland-Burnett states for optical
phase estimation. In particular, we discuss spontaneous four-wave mixing in
standard birefringent fibre as a source of pure, heralded single photons and
present methods of optimising such sources. We also outline a route to
programmable circuits which allow the control of photonic interactions even in
the presence of fabrication imperfections and describe a ratiometric
characterisation method for beam splitters which allows the characterisation of
complex circuits without the need for full process tomography. Finally, we
present a framework for performing state tomography on heralded states using
lossy measurement devices. This is motivated by a calculation of the effects of
fabrication imperfections on precision measurement using Holland-Burnett
states.Comment: 19 pages, 7 figure
Generating, manipulating and measuring entanglement and mixture with a reconfigurable photonic circuit
Entanglement is the quintessential quantum mechanical phenomenon understood
to lie at the heart of future quantum technologies and the subject of
fundamental scientific investigations. Mixture, resulting from noise, is often
an unwanted result of interaction with an environment, but is also of
fundamental interest, and is proposed to play a role in some biological
processes. Here we report an integrated waveguide device that can generate and
completely characterize pure two-photon states with any amount of entanglement
and arbitrary single-photon states with any amount of mixture. The device
consists of a reconfigurable integrated quantum photonic circuit with eight
voltage controlled phase shifters. We demonstrate that for thousands of
randomly chosen configurations the device performs with high fidelity. We
generate maximally and non-maximally entangled states, violate a Bell-type
inequality with a continuum of partially entangled states, and demonstrate
generation of arbitrary one-qubit mixed states.Comment: 6 pages, 6 figure
First bounds on the very high energy gamma-ray emission from Arp 220
Using the Major Atmospheric Gamma Imaging Cherenkov Telescope (MAGIC), we
have observed the nearest ultra-luminous infrared galaxy Arp 220 for about 15
hours. No significant signal was detected within the dedicated amount of
observation time. The first upper limits to the very high energy -ray
flux of Arp 220 are herein reported and compared with theoretical expectations.Comment: Accepted for publication in Ap
Experimental Quantum Hamiltonian Learning
Efficiently characterising quantum systems, verifying operations of quantum
devices and validating underpinning physical models, are central challenges for
the development of quantum technologies and for our continued understanding of
foundational physics. Machine-learning enhanced by quantum simulators has been
proposed as a route to improve the computational cost of performing these
studies. Here we interface two different quantum systems through a classical
channel - a silicon-photonics quantum simulator and an electron spin in a
diamond nitrogen-vacancy centre - and use the former to learn the latter's
Hamiltonian via Bayesian inference. We learn the salient Hamiltonian parameter
with an uncertainty of approximately . Furthermore, an observed
saturation in the learning algorithm suggests deficiencies in the underlying
Hamiltonian model, which we exploit to further improve the model itself. We go
on to implement an interactive version of the protocol and experimentally show
its ability to characterise the operation of the quantum photonic device. This
work demonstrates powerful new quantum-enhanced techniques for investigating
foundational physical models and characterising quantum technologies
Systematic search for VHE gamma-ray emission from X-ray bright high-frequency BL Lac objects
All but three (M87, BL Lac and 3C 279) extragalactic sources detected so far
at very high energy (VHE) gamma-rays belong to the class of high-frequency
peaked BL Lac (HBL) objects. This suggested to us a systematic scan of
candidate sources with the MAGIC telescope, based on the compilation of X-ray
blazars by Donato et al. (2001). The observations took place from December 2004
to March 2006 and cover sources on the northern sky visible under small zenith
distances zd < 30 degrees at culmination. The sensitivity of the search was
planned for detecting X-ray bright F(1 keV) > 2 uJy) sources emitting at least
the same energy flux at 200 GeV as at 1 keV. In order to avoid strong gamma-ray
attenuation close to the energy threshold, the redshift of the sources was
constrained to values z<0.3. Of the fourteen sources observed, 1ES 1218+304 and
1ES 2344+514 have been detected in addition to the known bright TeV blazars Mrk
421 and Mrk 501. A marginal excess of 3.5 sigma from the position of 1ES
1011+496 was observed and has been confirmed as a source of VHE gamma-rays by a
second MAGIC observation triggered by a high optical state (Albert et al.
2007). For the remaining sources, we present here the 99% confidence level
upper limits on the integral flux above ~200 GeV. We characterize the sample of
HBLs (including all HBLs detected at VHE so far) by looking for correlations
between their multi-frequency spectral indices determined from simultaneous
optical, archival X-ray, and radio luminosities, finding that the VHE emitting
HBLs do not seem to constitute a unique subclass. The absorption corrected
gamma-ray luminosities at 200 GeV of the HBLs are generally not higher than
their X-ray luminosities at 1 keV.Comment: 15 pages, 7 figures, 5 tables, submitted to ApJ (revised version
Discovery of Very High Energy -Rays from Markarian~180 Triggered by an Optical Outburst
The high-frequency-peaked BL Lacertae object Markarian~180 (Mrk~180) was
observed to have an optical outburst in 2006 March, triggering a Target of
Opportunity observation with the MAGIC telescope. The source was observed for
12.4 hr and very high energy -ray emission was detected with a
significance of 5.5 . An integral flux above 200 GeV of
was measured, corresponding to
11% of the Crab Nebula flux. A rather soft spectrum with a photon index of
has been determined. No significant flux variation was found.Comment: Accepted by ApJ Letters, minor revision
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