17 research outputs found
POSSIBLE USE OF DNAS IN SINGLE MOLECULE FORCE SPECTROSCOPY TO PROBE SINGLE PROTEIN UNFOLDING SIGNATURES
Master'sMASTER OF SCIENC
Protecting unknown two-qubit entangled states by nesting Uhrig's dynamical decoupling sequences
Future quantum technologies rely heavily on good protection of quantum
entanglement against environment-induced decoherence. A recent study showed
that an extension of Uhrig's dynamical decoupling (UDD) sequence can (in
theory) lock an arbitrary but known two-qubit entangled state to the th
order using a sequence of control pulses [Mukhtar et al., Phys. Rev. A 81,
012331 (2010)]. By nesting three layers of explicitly constructed UDD
sequences, here we first consider the protection of unknown two-qubit states as
superposition of two known basis states, without making assumptions of the
system-environment coupling. It is found that the obtained decoherence
suppression can be highly sensitive to the ordering of the three UDD layers and
can be remarkably effective with the correct ordering. The detailed theoretical
results are useful for general understanding of the nature of controlled
quantum dynamics under nested UDD. As an extension of our three-layer UDD, it
is finally pointed out that a completely unknown two-qubit state can be
protected by nesting four layers of UDD sequences. This work indicates that
when UDD is applicable (e.g., when environment has a sharp frequency cut-off
and when control pulses can be taken as instantaneous pulses), dynamical
decoupling using nested UDD sequences is a powerful approach for entanglement
protection.Comment: 11 pages, 3 figures, published versio
Universal Dynamical Decoupling: Two-Qubit States and Beyond
Uhrig's dynamical decoupling pulse sequence has emerged as one universal and
highly promising approach to decoherence suppression. So far both the
theoretical and experimental studies have examined single-qubit decoherence
only. This work extends Uhrig's universal dynamical decoupling from one-qubit
to two-qubit systems and even to general multi-level quantum systems. In
particular, we show that by designing appropriate control Hamiltonians for a
two-qubit or a multi-level system, Uhrig's pulse sequence can also preserve a
generalized quantum coherence measure to the order of , with only
pulses. Our results lead to a very useful scheme for efficiently locking
two-qubit entangled states. Future important applications of Uhrig's pulse
sequence in preserving the quantum coherence of multi-level quantum systems can
also be anticipated.Comment: 10 pages, 4 figures, minor changes made, submitted to PR
THE ROLE OF MECHANICS AND COLLECTIVE CELL CONSTRAINTS IN EPITHELIAL CELL DEATH AND EXTRUSION
Ph.DDOCTOR OF PHILOSOPH
Biological Tissues as Active Nematic Liquid Crystals
International audienc
Emergent patterns of collective cell migration under tubular confinement
Collective epithelial behaviours are studied in vitro in the context of flat sheets but a system to mimic tubular systems is lacking. Here, the authors develop a method to study collective behaviour in lumenal structures and show that several features depend on the extent of tubular confinement and/or curvature
Material approaches to active tissue mechanics
International audienc
Topological defects in epithelia govern cell death and extrusion
International audienc
Transepithelial potential difference governs epithelial homeostasis by electromechanics
International audienceStudies of electric effects in biological systems, from the work on action potential to studies on limb regeneration or wound healing, commonly focus on transitory behaviour and not on addressing the question of homeostasis. Here we use a microfluidic device to study how the homeostasis of confluent epithelial tissues is modified when a transepithelial potential difference that is different from the natural one is imposed on an epithelial layer. When the field direction matches the natural one, we can restore perfect confluence in an epithelial layer turned defective either by E-cadherin knockout or by weakening the cell-substrate adhesion; additionally, the tissue pushes on the substrate with kilopascal stress, inducing active-cell response such as death and differentiation. When the field is opposite, the tissue pulls with similar strengths, whereas homeostasis is destroyed by the perturbation of junctional actin and cell shapes, increased cell division rate and formation of mounds. Most of these observations can be quantitatively explained by an electrohydrodynamic theory involving local cytoplasmic electro-osmotic flows. We expect this work to motivate further studies on the long-time effects of electromechanical pathways with important tissue engineering applications