13,006 research outputs found
Ghost Interference with Optical Parametric Amplifier
The 'Ghost' interference experiment is analyzed when the source of entangled
photons is a multimode Optical Parametric Amplifier(OPA) whose weak limit is
the two-photon Spontaneous Parametric Downconversion(SPDC) beam. The visibility
of the double-slit pattern is calculated, taking the finite coincidence time
window of the photon counting detectors into account. It is found that the
coincidence window and the bandwidth of light reaching the detectors play a
crucial role in the loss of visibility on coincidence detection, not only in
the 'Ghost' interference experiment but in all experiments involving
coincidence detection. The differences between the loss of visibility with
two-mode and multimode OPA sources is also discussed.
PACS: 42.65.Yj, 42.50.Dv, 42.65.L
A silicon-based single-electron interferometer coupled to a fermionic sea
We study Landau-Zener-Stueckelberg-Majorana (LZSM) interferometry under the
influence of projective readout using a charge qubit tunnel-coupled to a
fermionic sea. This allows us to characterise the coherent charge qubit
dynamics in the strong-driving regime. The device is realised within a silicon
complementary metal-oxide-semiconductor (CMOS) transistor. We first read out
the charge state of the system in a continuous non-demolition manner by
measuring the dispersive response of a high-frequency electrical resonator
coupled to the quantum system via the gate. By performing multiple fast
passages around the qubit avoided crossing, we observe a multi-passage LZSM
interferometry pattern. At larger driving amplitudes, a projective measurement
to an even-parity charge state is realised, showing a strong enhancement of the
dispersive readout signal. At even larger driving amplitudes, two projective
measurements are realised within the coherent evolution resulting in the
disappearance of the interference pattern. Our results demonstrate a way to
increase the state readout signal of coherent quantum systems and replicate
single-electron analogues of optical interferometry within a CMOS transistor
Evidence of Double Phonon Excitations in ^{16}O + ^{208}Pb Reaction
The fusion cross-sections for ^{16}O + ^{208}Pb, measured to high precision,
enable the extraction of the distribution of fusion barriers. This shows a
structure markedly different from the single-barrier which might be expected
for fusion of two doubly-closed shell nuclei. The results of exact coupled
channel calculations performed to understand the observations are presented.
These calculations indicate that coupling to a double octupole phonon excited
state in ^{208}Pb is necessary to explain the experimental barrier
distributions.Comment: 6 pages, 2 figures, To be published in the Proceedings of the FUSION
97 Conference, South Durras, Australia, March 1997 (J. Phys. G
Fusion barrier distributions in systems with finite excitation energy
Eigen-channel approach to heavy-ion fusion reactions is exact only when the
excitation energy of the intrinsic motion is zero. In order to take into
account effects of finite excitation energy, we introduce an energy dependence
to weight factors in the eigen-channel approximation. Using two channel
problem, we show that the weight factors are slowly changing functions of
incident energy. This suggests that the concept of the fusion barrier
distribution still holds to a good approximation even when the excitation
energy of the intrinsic motion is finite. A transition to the adiabatic
tunneling, where the coupling leads to a static potential renormalization, is
also discussed.Comment: 9 pages, 4 figures, Submitted to Physical Review
Probing anharmonic properties of nuclear surface vibration by heavy-ion fusion reactions
Describing fusion reactions between ^{16}O and ^{154}Dy and, between ^{16}O
and ^{144}Sm by the and interacting boson model, we show that
heavy-ion fusion reactions are strongly affected by anharmonic properties of
nuclear surface vibrations and nuclear shape, and thus provide a powerful
method to study details of nuclear structure and dynamics.Comment: 8 pages, 5 figures, To be published in the Proceedings of the FUSION
97 Conference, South Durras, Australia, March 1997 (J. Phys. G
Monte Carlo studies of a novel X-ray tube anode design
When energetic electrons are incident on high atomic number absorbers, a substantial fraction is back-scattered. This phenomenon is responsible for several undesirable effects in X-ray tubes, in particular a reduction in the X-ray output. The extent of this shortfall has been estimated by using Monte Carlo simulation to start electrons at increasing depth inside the anode, the results indicating that an output enhancement of nearly 50% could be achieved in principle if the electrons wasted in back-scatter events could be trapped inside a tungsten anode. To test this idea a further set of simulations were done for a novel anode geometry. Results showed that X-ray tube efficiencies might be substantially enhanced by this approach.http://www.sciencedirect.com/science/article/B6TVT-43P41Y7-30/1/526566f6ea15332c302cdad2886e583
Addictive Technology and Its Implications for Antitrust Enforcement
The advent of mobile devices and digital media platforms in the past decade represents the biggest shock to cognition in human history. Robust medical evidence is emerging that digital media platforms are addictive and, when used in excess, harmful to users’ mental health. Other types of addictive products, like tobacco and prescription drugs, are heavily regulated to protect consumers. Currently, there is no regulatory structure protecting digital media users from these harms. Antitrust enforcement and regulation that lowers entry barriers could help consumers of social media by increasing competition. Economic theory tells us that more choice in digital media will increase the likelihood that some firms will vie to offer higher-quality and safer platforms. For this reason, evaluating harm to innovation (especially safety innovation) and product variety may be particularly important in social media merger and conduct cases. Another critical element to antitrust enforcement in this space is a correct accounting of social media’s addictive qualities. Standard antitrust analysis seeks to prohibit conduct that harms consumer welfare. Economists have taught the antitrust bar that the output of a product or service is a reliable proxy for consumer welfare. However, output and welfare do not have this relationship when a product is addictive. Indeed, in social media markets, increased output is often harmful. We argue that antitrust analysis must reject the output proxy and return to a focus on consumer welfare itself in cases involving addictive social media platforms. In particular, courts should reject defenses that rely only on gross output measures without evidence that any alleged increases in output actually benefit consumers
Magnon-photon coupling in the noncollinear magnetic insulator Cu 2 OSeO 3
Anticrossing behavior between magnons in the noncollinear chiral magnet Cu2OSeO3 and a two-mode X-band microwave resonator was studied in the temperature range 5–100 K. In the field-induced ferrimagnetic phase, we observed a strong-coupling regime between magnons and two microwave cavity modes with a cooperativity reaching 3600. In the conical phase, cavity modes are dispersively coupled to a fundamental helimagnon mode, and we demonstrate that the magnetic phase diagram of Cu2OSeO3 can be reconstructed from the measurements of the cavity resonance frequency. In the helical phase, a hybridized state of a higher-order helimagnon mode and a cavity mode—a helimagnon polariton—was found. Our results reveal a class of magnetic systems where strong coupling of microwave photons to nontrivial spin textures can be observed
Effect of oil palm sustainability certification on deforestation and fire in Indonesia.
Many major corporations and countries have made commitments to purchase or produce only "sustainable" palm oil, a commodity responsible for substantial tropical forest loss. Sustainability certification is the tool most used to fulfill these procurement policies, and around 20% of global palm oil production was certified by the Roundtable on Sustainable Palm Oil (RSPO) in 2017. However, the effect of certification on deforestation in oil palm plantations remains unclear. Here, we use a comprehensive dataset of RSPO-certified and noncertified oil palm plantations (∼188,000 km2) in Indonesia, the leading producer of palm oil, as well as annual remotely sensed metrics of tree cover loss and fire occurrence, to evaluate the impact of certification on deforestation and fire from 2001 to 2015. While forest loss and fire continued after RSPO certification, certified palm oil was associated with reduced deforestation. Certification lowered deforestation by 33% from a counterfactual of 9.8 to 6.6% y-1 Nevertheless, most plantations contained little residual forest when they received certification. As a result, by 2015, certified areas held less than 1% of forests remaining within Indonesian oil palm plantations. Moreover, certification had no causal impact on forest loss in peatlands or active fire detection rates. Broader adoption of certification in forested regions, strict requirements to avoid all peat, and routine monitoring of clearly defined forest cover loss in certified and RSPO member-held plantations appear necessary if the RSPO is to yield conservation and climate benefits from reductions in tropical deforestation
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