33 research outputs found
Non-Markovian quantum dynamics: local versus non-local
We analyze non-Markovian evolution of open quantum systems. It is shown that
any dynamical map representing evolution of such a system may be described
either by non-local master equation with memory kernel or equivalently by
equation which is local in time. These two descriptions are complementary: if
one is simple the other is quite involved, or even singular, and vice versa.
The price one pays for the local approach is that the corresponding generator
keeps the memory about the starting point `t_0'. This is the very essence of
non-Markovianity. Interestingly, this generator might be highly singular,
nevertheless, the corresponding dynamics is perfectly regular. Remarkably,
singularities of generator may lead to interesting physical phenomena like
revival of coherence or sudden death and revival of entanglement.Comment: 4.5 pages; new examples are adde
On the structure of entanglement witnesses and new class of positive indecomposable maps
We construct a new class of positive indecomposable maps in the algebra of 'd
x d' complex matrices. Each map is uniquely characterized by a cyclic
bistochastic matrix. This class generalizes a Choi map for d=3. It provides a
new reach family of indecomposable entanglement witnesses which define
important tool for investigating quantum entanglement.Comment: 18 page
General form of quantum evolution
We propose a complete treatment of a local in time dynamics of open quantum
systems. In this approach Markovian evolution turns out to be a special case of
a general non-Markovian one. We provide a general representation of the local
generator which generalizes well known Lindblad representation for the
Markovian dynamics. It shows that the structure of non-Markovian generators is
highly intricate and the problem of their classification is still open. Simple
examples illustrate our approach.Comment: 4 page
From Markovian semigroup to non-Markovian quantum evolution
We provided a class of legitimate memory kernels leading to completely
positive trace preserving dynamical maps. Our construction is based on a simple
normalization procedure. Interestingly, when applied to the celebrated
Wigner-Weisskopf theory it gives the standard Markovian evolution governed by
the local master equation.Comment: 8 page
Multipartite circulant states with positive partial transposes
We construct a large class of multipartite qudit states which are positive
under the family of partial transpositions. The construction is based on
certain direct sum decomposition of the total Hilbert space displaying
characteristic circular structure and hence generalizes a class of bipartite
circulant states proposed recently by the authors. This class contains many
well known examples of multipartite quantum states from the literature and
gives rise to a huge family of completely new states.Comment: 14 pages; minor change
Rotationally invariant multipartite states
We construct a class of multipartite states possessing rotational SO(3)
symmetry -- these are states of K spin-j_A particles and K spin-j_B particles.
The construction of symmetric states follows our two recent papers devoted to
unitary and orthogonal multipartite symmetry. We study basic properties of
multipartite SO(3) symmetric states: separability criteria and multi-PPT
conditions.Comment: 18 pages; new reference
On partially entanglement breaking channels
Using well known duality between quantum maps and states of composite systems
we introduce the notion of Schmidt number of a quantum channel. It enables one
to define classes of quantum channels which partially break quantum
entanglement. These classes generalize the well known class of entanglement
breaking channels.Comment: 9 page
A new class of states with positive partial transposition
We construct a new class of PPT states for bipartite "d x d" systems. This
class is invariant under the maximal commutative subgroup of U(d) and contains
as special cases almost all known examples of PPT states. Theses states may be
used to test the atomic property of positive maps which are crucial in studying
quantum entanglement.Comment: 4.5 page
Antibody-Mediated Rejection: An Evolving Entity in Heart Transplantation
Antibody-mediated rejection (AMR) is gaining increasing recognition as a major complication after heart transplantation, posing a significant risk for allograft failure, cardiac allograft vasculopathy, and poor survival. AMR results from activation of the humoral immune arm and the production of donor-specific antibodies (DSA) that bind to the cardiac allograft causing myocardial injury predominantly through complement activation. The diagnosis of AMR has evolved from a clinical diagnosis involving allograft dysfunction and the presence of DSA to a primarily pathologic diagnosis based on histopathology and immunopathology. Treatment for AMR is multifaceted, targeting inhibition of the humoral immune system at different levels with emerging agents including proteasome and complement inhibitors showing particular promise. While there have been significant advances in our current understanding of the pathogenesis, diagnosis, and treatment of AMR, further research is required to determine optimal diagnostic tools, therapeutic agents, and timing of treatment
Tankyrase represses autoinflammation through the attenuation of TLR2 signaling
Dysregulation of Toll-like receptor (TLR) signaling contributes to the pathogenesis of autoimmune diseases. Here, we provide genetic evidence that tankyrase, a member of the poly(ADP-ribose) polymerase (PARP) family, negatively regulates TLR2 signaling. We show that mice lacking tankyrase in myeloid cells developed severe systemic inflammation with high serum inflammatory cytokine levels. We provide mechanistic evidence that tankyrase deficiency resulted in tyrosine phosphorylation and activation of TLR2 and show that phosphorylation of tyrosine 647 within the TIR domain by SRC and SYK kinases was critical for TLR2 stabilization and signaling. Last, we show that the elevated cytokine production and inflammation observed in mice lacking tankyrase in myeloid cells were dependent on the adaptor protein 3BP2, which is required for SRC and SYK activation. These data demonstrate that tankyrase provides a checkpoint on the TLR-mediated innate immune response