3,412 research outputs found
Superradiance-like Electron Transport through a Quantum Dot
We theoretically show that intriguing features of coherent many-body physics
can be observed in electron transport through a quantum dot (QD). We first
derive a master equation based framework for electron transport in the
Coulomb-blockade regime which includes hyperfine (HF) interaction with the
nuclear spin ensemble in the QD. This general tool is then used to study the
leakage current through a single QD in a transport setting. We find that, for
an initially polarized nuclear system, the proposed setup leads to a strong
current peak, in close analogy with superradiant emission of photons from
atomic ensembles. This effect could be observed with realistic experimental
parameters and would provide clear evidence of coherent HF dynamics of nuclear
spin ensembles in QDs.Comment: 21 pages, 10 figure
Steady-state negative Wigner functions of nonlinear nanomechanical oscillators
We propose a scheme to prepare nanomechanical oscillators in nonclassical
steady states, characterized by a pronounced negative Wigner function. In our
optomechanical approach, the mechanical oscillator couples to multiple laser
driven resonances of an optical cavity. By lowering the resonance frequency of
the oscillator via an inhomogeneous electrostatic field, we significantly
enhance its intrinsic geometric nonlinearity per phonon. This causes the
motional sidebands to split into separate spectral lines for each phonon number
and transitions between individual phonon Fock states can be selectively
addressed. We show that this enables the preparation of the nanomechanical
oscillator in a single phonon Fock state. Our scheme can for example be
implemented with a carbon nanotube dispersively coupled to the evanescent field
of a state of the art whispering gallery mode microcavity
Nuclear Spin Dynamics in Double Quantum Dots: Multi-Stability, Dynamical Polarization, Criticality and Entanglement
We theoretically study the nuclear spin dynamics driven by electron transport
and hyperfine interaction in an electrically-defined double quantum dot (DQD)
in the Pauli-blockade regime. We derive a master-equation-based framework and
show that the coupled electron-nuclear system displays an instability towards
the buildup of large nuclear spin polarization gradients in the two quantum
dots. In the presence of such inhomogeneous magnetic fields, a quantum
interference effect in the collective hyperfine coupling results in sizable
nuclear spin entanglement between the two quantum dots in the steady state of
the evolution. We investigate this effect using analytical and numerical
techniques, and demonstrate its robustness under various types of
imperfections.Comment: 35 pages, 19 figures. This article provides the full analysis of a
scheme proposed in Phys. Rev. Lett. 111, 246802 (2013). v2: version as
publishe
Solid-state magnetic traps and lattices
We propose and analyze magnetic traps and lattices for electrons in
semiconductors. We provide a general theoretical framework and show that
thermally stable traps can be generated by magnetically driving the particle's
internal spin transition, akin to optical dipole traps for ultra-cold atoms.
Next we discuss in detail periodic arrays of magnetic traps, i.e. magnetic
lattices, as a platform for quantum simulation of exotic Hubbard models, with
lattice parameters that can be tuned in real time. Our scheme can be readily
implemented in state-of-the-art experiments, as we particularize for two
specific setups, one based on a superconducting circuit and another one based
on surface acoustic waves.Comment: 18 pages, 8 figure
Multi-locus barcoding confirms the occurrence of Elegant Tern in Western Europe
We are very grateful to the following people who helped in various ways with sample collection: JĂ©rome Fuchs and Eric Pasquet (National Museum of Natural History, Paris), Sharon M. Birks (Burke Museum of Naturel History of Seattle), Charlotte Francesiaz, Benjamin Vollot and Gilles Balança (Sandwich Tern, France), Charles Collins (Elegant Tern, USA), Arnaud Lenoble (Royal Tern, Guadeloupe), Lorien Pichegru (Crested Tern, South Africa), Abdulmaula Hamza (Lesser Crested Tern, Libya) and Clive Barlow (The Gambia). Marcio Efe and Eli Bridge helped with genotyping and shared unpublished sequences. We thank Juan Antonio GĂłmez for advice and Miguel ChardĂ and Francisco Javier GarcĂa-Gans for field assistance in Valencia (Spain). Mathias Grandpierre (SociĂ©tĂ© pour lâEtude et lâAmĂ©nagement de la Nature dans le Sud-Ouest) helped with fieldwork at the Banc dâArguin (France). All the experiments comply with the current laws of the country in which they were performed.Peer reviewedPostprin
- âŠ