200 research outputs found
Direct microwave measurement of Andreev-bound-state dynamics in a proximitized semiconducting nanowire
The modern understanding of the Josephson effect in mesosopic devices derives
from the physics of Andreev bound states, fermionic modes that are localized in
a superconducting weak link. Recently, Josephson junctions constructed using
semiconducting nanowires have led to the realization of superconducting qubits
with gate-tunable Josephson energies. We have used a microwave circuit QED
architecture to detect Andreev bound states in such a gate-tunable junction
based on an aluminum-proximitized InAs nanowire. We demonstrate coherent
manipulation of these bound states, and track the bound-state fermion parity in
real time. Individual parity-switching events due to non-equilibrium
quasiparticles are observed with a characteristic timescale . The of a topological nanowire
junction sets a lower bound on the bandwidth required for control of Majorana
bound states
Measurement of the Lifetime of the Metastable 5d\u3csub\u3e3/2\u3c/sub\u3e26d\u3csub\u3e3/2\u3c/sub\u3e, J=0 Autoionizing State of Barium
We report a measurement of the lifetime of the metastable 5d3/226d3/2, J=0 autoionizing state of barium. We have determined the lifetime to be 190(10) ns
Two-Step Stabilization of Autoionizing States
A two-step process using internal conversion and fluorescence to stabilize the 6P3/211d autoionizing state of barium has been observed. The internal conversion produces very highly excited autoionizing Rydberg states, which then emit fluorescence to produce singly excited, bound states. Inclusion of this process should bring calculations closer to agreement with recent measurements of dielectronic recombination
Realization of microwave quantum circuits using hybrid superconducting-semiconducting nanowire Josephson elements
We report the realization of quantum microwave circuits using hybrid
superconductor-semiconductor Josephson elements comprised of InAs nanowires
contacted by NbTiN. Capacitively-shunted single elements behave as transmon
qubits with electrically tunable transition frequencies. Two-element circuits
also exhibit transmon-like behavior near zero applied flux, but behave as flux
qubits at half the flux quantum, where non-sinusoidal current-phase relations
in the elements produce a double-well Josephson potential. These hybrid
Josephson elements are promising for applications requiring microwave
superconducting circuits operating in magnetic field.Comment: Main text: 4 pages, 4 figures; Supplement: 10 pages, 8 figures, 1
tabl
In-situ Tuning of the Electric Dipole Strength of a Double Dot Charge Qubit: Charge Noise Protection and Ultra Strong Coupling
Semiconductor quantum dots, where electrons or holes are isolated via
electrostatic potentials generated by surface gates, are promising building
blocks for semiconductor-based quantum technology. Here, we investigate double
quantum dot (DQD) charge qubits in GaAs, capacitively coupled to high-impedance
SQUID array and Josephson junction array resonators. We tune the strength of
the electric dipole interaction between the qubit and the resonator in-situ
using surface gates. We characterize the qubit-resonator coupling strength,
qubit decoherence, and detuning noise affecting the charge qubit for different
electrostatic DQD configurations. We find that all quantities can be tuned
systematically over more than one order of magnitude, resulting in reproducible
decoherence rates MHz in the limit of high interdot
capacitance. Conversely, by reducing the interdot capacitance, we can increase
the DQD electric dipole strength, and therefore its coupling to the resonator.
By employing a Josephson junction array resonator with an impedance of
k and a resonance frequency of GHz, we observe
a coupling strength of MHz, demonstrating the possibility to
achieve the ultrastrong coupling regime (USC) for electrons hosted in a
semiconductor DQD. These results are essential for further increasing the
coherence of quantum dot based qubits and investigating USC physics in
semiconducting QDs.Comment: 24 pages, 13 figure
Front versus rear side light-ion acceleration from high-intensity laser–solid interactions
The source of ions accelerated from high-intensity laser interactions with thin foil targets is investigated by coating a deuterated plastic layer either on the front, rear or both surfaces of thin foil targets. The originating surface of the deuterons is therefore known and this method is used to assess the relative source contributions and maximum energies using a Thomson parabola spectrometer to obtain high-resolution light-ion spectra. Under these experimental conditions, laser intensity of (0.5–2.5) _ 10 19 W cm _2 , pulse duration of 400 fs and target thickness of 6–13 µm, deuterons originating from the front surface can gain comparable maximum energies as those from the rear surface and spectra from either side can deviate from Maxwellian. Two-dimensional particle-in-cell simulations model the acceleration and show that any presence of a proton rich contamination layer over the surface is detrimental to the deuteron acceleration from the rear surface, whereas it is likely to be less influential on the front side acceleration mechanism.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/90782/1/0741-3335_53_1_014011.pd
Introduction: Examined Live – An Epistemological Exchange Between Philosophy and Cultural Psychology on Reflection
Besides the general agreement about the human capability of reflection, there is a large area of disagreement and debate about the nature and value of “reflective scrutiny” and the role of “second-order states” in everyday life. This problem has been discussed in a vast and heterogeneous literature about topics such as epistemic injustice, epistemic norms, agency, understanding, meta-cognition etc. However, there is not yet any extensive and interdisciplinary work, specifically focused on the topic of the epistemic value of reflection. This volume is one of the first attempts aimed at providing an innovative contribution, an exchange between philosophy, epistemology and psychology about the place and value of reflection in everyday life.
Our goal in the next sections is not to offer an exhaustive overview of recent work on epistemic reflection, nor to mimic all of the contributions made by the chapters in this volume. We will try to highlight some topics that have motivated a new resumption of this field and, with that, drawing on chapters from this volume where relevant.
Two elements defined the scope and content of this volume, on the one hand, the crucial contribution of Ernest Sosa, whose works provide original and thought-provoking contributions to contemporary epistemology in setting a new direction for old dilemmas about the nature and value of knowledge, giving a central place to reflection. On the other hand, the recent developments of cultural psychology, in the version of the “Aalborg approach”, reconsider the object and scope of psychological sciences, stressing that “[h]uman conduct is purposeful”
Comparison of bulk and pitcher-catcher targets for laser-driven neutron production
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/98756/1/PhysPlasmas_18_083106.pd
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