7 research outputs found
Quantum interference of tunneling paths under a double-well barrier
The tunnel effect, a hallmark of the quantum realm, involves motion across a
classically forbidden region. In a driven nonlinear system, two or more
tunneling paths may coherently interfere, enhancing or cancelling the tunnel
effect. Since individual quantum systems are difficult to control, this
interference effect has only been studied for the lowest energy states of
many-body ensembles. In our experiment, we show a coherent cancellation of the
tunneling amplitude in the ground and excited state manifold of an individual
squeeze-driven Kerr oscillator, a consequence of the destructive interference
of tunneling paths in the classically forbidden region. The tunnel splitting
vanishes periodically in the spectrum as a function of the frequency of the
squeeze-drive, with the periodicity given by twice the Kerr coefficient. This
resonant cancellation, combined with an overall exponential reduction of
tunneling as a function of both amplitude and frequency of the squeeze-drive,
reduces drastically the well-switching rate under incoherent
environment-induced evolution. The control of tunneling via interference
effects can be applied to quantum computation, molecular, and nuclear physics
Towards quantum simulation with circular Rydberg atoms
The main objective of quantum simulation is an in-depth understanding of
many-body physics. It is important for fundamental issues (quantum phase
transitions, transport, . . . ) and for the development of innovative
materials. Analytic approaches to many-body systems are limited and the huge
size of their Hilbert space makes numerical simulations on classical computers
intractable. A quantum simulator avoids these limitations by transcribing the
system of interest into another, with the same dynamics but with interaction
parameters under control and with experimental access to all relevant
observables. Quantum simulation of spin systems is being explored with trapped
ions, neutral atoms and superconducting devices. We propose here a new paradigm
for quantum simulation of spin-1/2 arrays providing unprecedented flexibility
and allowing one to explore domains beyond the reach of other platforms. It is
based on laser-trapped circular Rydberg atoms. Their long intrinsic lifetimes
combined with the inhibition of their microwave spontaneous emission and their
low sensitivity to collisions and photoionization make trapping lifetimes in
the minute range realistic with state-of-the-art techniques. Ultra-cold
defect-free circular atom chains can be prepared by a variant of the
evaporative cooling method. This method also leads to the individual detection
of arbitrary spin observables. The proposed simulator realizes an XXZ spin-1/2
Hamiltonian with nearest-neighbor couplings ranging from a few to tens of kHz.
All the model parameters can be tuned at will, making a large range of
simulations accessible. The system evolution can be followed over times in the
range of seconds, long enough to be relevant for ground-state adiabatic
preparation and for the study of thermalization, disorder or Floquet time
crystals. This platform presents unrivaled features for quantum simulation
Extreme homozygosity in Southern Hemisphere populations of Deladenus siricidicola, a biological control agent of Sirex noctilio
The woodwasp Sirex noctilio, together with its mutualistic fungal symbiont Amylostereum
areolatum, is the most damaging invasive pest of Pinus spp. in the Southern Hemisphere. The
nematode Deladenus siricidicola parasitizes S. noctilio larvae and is the most effective biological
control agent against this woodwasp. Nothing is known regarding the genetic diversity of D.
siricidicola, even though such knowledge would be invaluable in improving sustainable
biological control programs. The aim of this study was to develop microsatellite markers to study
the genetic diversity of D siricidicola populations. Microsatellite enrichment was performed
using Fast Isolation by AFLP of Sequences Containing repeats (FIASCO) and fragments were
then sequenced using 454 GS-FLX pyrosequencing. From the 1.2 megabases of sequence data,
166 microsatellite containing contigs were identified. Twenty-six primer pairs were designed
using the web-based program Primer3 and screened for polymorphism in populations of the
nematode from different sources in the Southern Hemisphere. Seventeen primers amplified
microsatellite-containing loci of interest. No length polymorphism was present in any of the
microsatellite repeats in these populations. Regions flanking the microsatellites also showed no
polymorphism, except for one transition observed in an Argentinean strain for locus Ds316.
Twelve of the loci showed polymorphism between the Southern Hemisphere and Canadian
sources of D. siricidicola. The lack of diversity in Southern Hemisphere populations of D.
siricidicola could affect the ability of this nematode to adapt to different environments and host
types where it is used in biological control programs, and should thus be considered as a factor in
future control strategies and research projects.We thank the University of Pretoria, the National Research Foundation, members of the Tree
Protect Co-operative Program and THRIP funding from the Department of Trade and Industry,
South Africa, for financial support. We also thank the Mandela Rhodes Foundation for financial
support for the first author.http://www.elsevier.com/locate/ybconnf201