317 research outputs found
Dissipative stabilization of entangled cat states using a driven Bose-Hubbard dimer
We analyze a modified Bose-Hubbard model, where two cavities having on-site
Kerr interactions are subject to two-photon driving and correlated dissipation.
We derive an exact solution for the steady state of this interacting
driven-dissipative system, and use it show that the system permits the
preparation and stabilization of pure entangled non-Gaussian states, so-called
entangled cat states. Unlike previous proposals for dissipative stabilization
of such states, our approach requires only a linear coupling to a single
engineered reservoir (as opposed to nonlinear couplings to two or more
reservoirs). Our scheme is within the reach of state-of-the-art experiments in
circuit QED.Comment: 5 pages main text, 5 pages appendices, 6 figure
Stabilizing two-qubit entanglement with engineered synthetic squeezing
It is well known that qubits immersed in a squeezed vacuum environment
exhibit many exotic phenomena, including dissipative entanglement
stabilization. Here, we show that these effects only require interference
between excitation and decay processes, and can be faithfully mimicked without
non-classical light using simple classical temporal modulation. We present
schemes that harnesses this idea to stabilize entanglement between two remote
qubits coupled via a transmission line or waveguide, where either the
qubit-waveguide coupling is modulated, or the qubits are directly driven. We
analyze the resilience of these approaches against various imperfections, and
also characterize the trade-off between the speed and quality of entanglement
stabilization. Our protocols are compatible with state of the art cavity QED
systems.Comment: 16 pages, 6 figure
Simultaneous readout of two charge qubits
We consider a system of two solid state charge qubits, coupled to a single
read-out device, consisting of a single-electron transistor (SET). The
conductance of each tunnel junction is influenced by its neighboring qubit, and
thus the current through the transistor is determined by the qubits' state. The
full counting statistics of the electrons passing the transistor is calculated,
and we discuss qubit dephasing, as well as the quantum efficiency of the
readout. The current measurement is then compared to readout using real-time
detection of the SET island's charge state. For the latter method we show that
the quantum efficiency is always unity. Comparing the two methods a simple
geometrical interpretation of the quantum efficiency of the current measurement
appears. Finally, we note that full quantum efficiency in some cases can be
achieved measuring the average charge of the SET island, in addition to the
average current.Comment: 11 pages with 5 figure
Sequential Strong Measurements and Heat Vision
We study scenarios where a finite set of non-demolition von-Neumann
measurements are available. We note that, in some situations, repeated
application of such measurements allows estimating an infinite number of
parameters of the initial quantum state, and illustrate the point with a
physical example. We then move on to study how the system under observation is
perturbed after several rounds of projective measurements. While in the finite
dimensional case the effect of this perturbation always saturates, there are
some instances of infinite dimensional systems where such a perturbation is
accumulative, and the act of retrieving information about the system increases
its energy indefinitely (i.e., we have `Heat Vision'). We analyze this effect
and discuss a specific physical system with two dichotomic von-Neumann
measurements where Heat Vision is expected to show.Comment: See the Appendix for weird examples of heat visio
Improving transferability of introduced species' distribution models: new tools to forecast the spread of a highly invasive seaweed
Extent: 13 p.The utility of species distribution models for applications in invasion and global change biology is critically dependent on their transferability between regions or points in time, respectively. We introduce two methods that aim to improve the transferability of presence-only models: density-based occurrence thinning and performance-based predictor selection. We evaluate the effect of these methods along with the impact of the choice of model complexity and geographic background on the transferability of a species distribution model between geographic regions. Our multifactorial experiment focuses on the notorious invasive seaweed Caulerpa cylindracea (previously Caulerpa racemosa var. cylindracea) and uses Maxent, a commonly used presence-only modeling technique. We show that model transferability is markedly improved by appropriate predictor selection, with occurrence thinning, model complexity and background choice having relatively minor effects. The data shows that, if available, occurrence records from the native and invaded regions should be combined as this leads to models with high predictive power while reducing the sensitivity to choices made in the modeling process. The inferred distribution model of Caulerpa cylindracea shows the potential for this species to further spread along the coasts of Western Europe, western Africa and the south coast of Australia.Heroen Verbruggen, Lennert Tyberghein, Gareth S. Belton, Frederic Mineur, Alexander Jueterbock, Galice Hoarau, C. Frederico D. Gurgel, Olivier De Clerc
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