Sea-level change and storm surges in the context of climate change

This paper reviews the latest research in New Zealand surrounding the issues of sea-level rise and extreme sea levels in the context of global warming and variability in the Pacific-wide El Nino– Southern Oscillation (ENSO). Past records of climate, sea level (excluding tides) and sea and air temperatures have shown that they are continuously fluctuating over various long-term timescales of years, decades and centuries. This has made it very difficult to determine whether the anthropogenic effects such as increased levels of “greenhouse” gases are having an accelerating effect on global sea levels or an increased incidence of extreme storms. Over the past century, global sea level has risen by 10–25 cm, and is in line with the rise in relative sea level at New Zealand’s main ports of +1.7 mm yr –1. What has become very clear is the need to better understand interannual (year-to-year) and decadal variability in sea-level, as these larger signals of the order of 5–15 cm in annual-mean sea level have a significant “flow-on” effect on the long-term trend in sea level. The paper describes sea level variability in northern New Zealand—both long- and short-term—involved in assessing the regional trends in sea level. The paper also discusses the relative contributions of tides, barometric pressure and wind set-up in causing extreme sea levels during storm surges. Some recent research also looked at a related question—Is there any sign of increased storminess, and hence storm surge, in northern New Zealand due to climate change? The paper concludes that, while no one can be completely sure how sea-level and the degree of storminess will respond in the near future, what is clear is that interannual and decadal variability in sea level is inextricably linked with Pacific-wide ENSO response and longer inter-decadal shifts in the Pacific climate regime, such as the latest shift in 1976

Single-spin magnetometry with multi-pulse sensing sequences

We experimentally demonstrate single-spin magnetometry with multi-pulse sensing sequences. The use of multi-pulse sequences can greatly increase the sensing time per measurement shot, resulting in enhanced ac magnetic field sensitivity. We theoretically derive and experimentally verify the optimal number of sensing cycles, for which the effects of decoherence and increased sensing time are balanced. We perform these experiments for oscillating magnetic fields with fixed phase as well as for fields with random phase. Finally, by varying the phase and frequency of the ac magnetic field, we measure the full frequency-filtering characteristics of different multi-pulse schemes and discuss their use in magnetometry applications.Comment: 4 pages, 4 figures. Final versio

Entanglement genesis by ancilla-based parity measurement in 2D circuit QED

We present an indirect two-qubit parity meter in planar circuit quantum electrodynamics, realized by discrete interaction with an ancilla and a subsequent projective ancilla measurement with a dedicated, dispersively coupled resonator. Quantum process tomography and successful entanglement by measurement demonstrate that the meter is intrinsically quantum non-demolition. Separate interaction and measurement steps allow commencing subsequent data qubit operations in parallel with ancilla measurement, offering time savings over continuous schemes.Comment: 5 pages, 4 figures; supplemental material with 5 figure

Volcanic Generation of Tsunamis: Two New Zealand Palaeo-Events

Rapid emplacement of a mass via pyroclastic flows, or edifice failure, generates volcanic tsunamis. Physical modelling demonstrates that the efficiency of tsuna-mi generation is influenced by the angle the mass enters the ocean. Efficiency de-creases with increasing slope angle from 20° to 60°, before increasing to a maxi-mum at 90°, which corresponds to a mass falling directly into the ocean without interacting with the slope (impact tsunami). Further, in the case of surging pyro-clastic flows or regressive failures, successive closely spaced events may generate larger tsunami waves than a single event of comparable volume. It is difficult to assess if physical model results are meaningful for real world tsu-nami events due to limited observational data. This paper compares numerical models developed from physical simulations with palaeotsunami deposits from two New Zealand palaeo-events – pyroclastic flows from Mt Tarawera and edi-fice failure at Whakaari (White Island) – which constrains numerical simulations of the source mechanisms. The Mt Tarawera event involved multiple pyroclastic flows entering a lake during the AD 1314±12 Kaharoa Eruption. The interaction of multiple closely spaced pyroclastic flows is necessary to generate the 6-7 m maximum wave height inferred from near source tsunami deposits. Tsunami de-posits in the Bay of Plenty, dated to 2962±52 BP, are consistent with edifice fail-ure at Whakaari. In this case a single event with a volume of 0.23 km3 is suffi-cient to account for the tsunami deposits. Hence, if the failure was regressive, the successive stages were sufficiently close together to be indistinguishable from a large single event

Nanopositioning of a diamond nanocrystal containing a single NV defect center

Precise control over the position of a single quantum object is important for many experiments in quantum science and nanotechnology. We report on a technique for high-accuracy positioning of individual diamond nanocrystals. The positioning is done with a home-built nanomanipulator under real-time scanning electron imaging, yielding an accuracy of a few nanometers. This technique is applied to pick up, move and position a single NV defect center contained in a diamond nanocrystal. We verify that the unique optical and spin properties of the NV center are conserved by the positioning process.Comment: 3 pages, 3 figures; high-resolution version available at http://www.ns.tudelft.nl/q

Bootstrap tomography of high-precision pulses for quantum control

Long-time dynamical decoupling and quantum control of qubits require high-precision control pulses. Full characterization (quantum tomography) of imperfect pulses presents a bootstrap problem: tomography requires initial states of a qubit which can not be prepared without imperfect pulses. We present a protocol for pulse error analysis, specifically tailored for a wide range of the single solid-state electron spins. Using a single electron spin of a nitrogen-vacancy (NV) center in diamond, we experimentally verify the correctness of the protocol, and demonstrate its usefulness for quantum control tasks

Reversing quantum trajectories with analog feedback

We demonstrate the active suppression of transmon qubit dephasing induced by dispersive measurement, using parametric amplification and analog feedback. By real-time processing of the homodyne record, the feedback controller reverts the stochastic quantum phase kick imparted by the measurement on the qubit. The feedback operation matches a model of quantum trajectories with measurement efficiency $\tilde{\eta} \approx 0.5$, consistent with the result obtained by postselection. We overcome the bandwidth limitations of the amplification chain by numerically optimizing the signal processing in the feedback loop and provide a theoretical model explaining the optimization result.Comment: 5 pages, 4 figures, and Supplementary Information (7 figures

Theory of pinning in a Superconducting Thin Film Pierced by a Ferromagnetic Columnar Defect

This is an analytical study of pinning and spontaneous vortex phase is a system consisting of a superconducting thin film pierced by a long ferromagnetic columnar defect of finite radius $R$. The magnetic fields, screening currents, energy and pinning forces for this system are calculated. The interaction between the magnetic field of vortices and the magnetization outside the plane of the film and its close proximity enhances vortex pinning significantly. Spontaneous vortex phase appears when the magnetization of the columnar defect is increased above a critical value. Transitions between phases characterized by different number of flux quanta are also studied. These results are generalized to the case when the superconductor is pierced by an array of columnar defects.Comment: 6 pages, 4 figures, Accepted for publication in Phys. Rev.