1,363 research outputs found
Entangling power of baker's map: Role of symmetries
The quantum baker map possesses two symmetries: a canonical "spatial"
symmetry, and a time-reversal symmetry. We show that, even when these features
are taken into account, the asymptotic entangling power of the baker's map does
not always agree with the predictions of random matrix theory. We have verified
that the dimension of the Hilbert space is the crucial parameter which
determines whether the entangling properties of the baker are universal or not.
For power-of-two dimensions, i.e., qubit systems, an anomalous entangling power
is observed; otherwise the behavior of the baker is consistent with random
matrix theories. We also derive a general formula that relates the asymptotic
entangling power of an arbitrary unitary with properties of its reduced
eigenvectors.Comment: 5 page
Matrix Element Distribution as a Signature of Entanglement Generation
We explore connections between an operator's matrix element distribution and
its entanglement generation. Operators with matrix element distributions
similar to those of random matrices generate states of high multi-partite
entanglement. This occurs even when other statistical properties of the
operators do not conincide with random matrices. Similarly, operators with some
statistical properties of random matrices may not exhibit random matrix element
distributions and will not produce states with high levels of multi-partite
entanglement. Finally, we show that operators with similar matrix element
distributions generate similar amounts of entanglement.Comment: 7 pages, 6 figures, to be published PRA, partially supersedes
quant-ph/0405053, expands quant-ph/050211
Mycobacterial immune reconstitution inflammatory syndrome in HIV-1 infection after antiretroviral therapy is associated with deregulated specific T-cell responses: Beneficial effect of IL-2 and GM-CSF immunotherapy
BACKGROUND: With the advent of antiretroviral therapy (ART) cases of immune reconstitution inflammatory syndrome (IRIS) have increasingly been reported. IRIS usually occurs in individuals with a rapidly rising CD4 T-cell count or percentage upon initiation of ART, who develop a deregulated immune response to infection with or without reactivation of opportunistic organisms. Here, we evaluated rises in absolute CD4 T-cells, and specific CD4 T-cell responses in 4 HIV-1(+ )individuals presenting with mycobacterial associated IRIS who received in conjunction with ART, IL-2 plus GM-CSF immunotherapy. METHODS: We assessed CD4 T-cell counts, HIV-1 RNA loads, phenotype for naïve and activation markers, and in vitro proliferative responses. Results were compared with those observed in 11 matched, successfully treated asymptomatic clinical progressors (CP) with no evidence of opportunistic infections, and uninfected controls. RESULTS: Median CD4 T-cell counts in IRIS patients rose from 22 cells/μl before initiation of ART, to 70 cells/μl after 8 months of therapy (median 6.5 fold increase). This coincided with IRIS diagnosis, lower levels of naïve CD4 T-cells, increased expression of immune activation markers, and weak CD4 T-cell responses. In contrast, CP had a median CD4 T-cell counts of 76 cells/μl at baseline, which rose to 249 cells/μl 6 months post ART, when strong T-cell responses were seen in > 80% of patients. Higher levels of expression of immune activation markers were seen in IRIS patients compared to CP and UC (IRIS > CP > UC). Immunotherapy with IL-2 and GM-CSF paralleled clinical recovery. CONCLUSION: These data suggest that mycobacterial IRIS is associated with inadequate immune reconstitution rather than vigorous specific T-cell responses, and concomitant administration of IL-2 and GM-CSF immunotherapy with effective ART may correct/augment T-cell immunity in such setting resulting in clinical benefit
Latent tuberculosis infection screening and treatment in HIV: insights from evaluation of UK practice
Latent TB infection (LTBI) screening and treatment in HIV-positive individuals in the UK is advocated by the British HIV Association (BHIVA) and National Institute for Health and Care Excellence (NICE), although each recommends differing strategies. We undertook an evaluation of UK practice, relating the responses to the local HIV/TB disease burden. 162 of 188 (86%) UK geographical areas responded; only 93/162 (57.4%) offer LTBI testing with considerable heterogeneity in practice, and no difference in HIV/TB burden between areas offering testing and those who do not. Only 33/93 (35.5%) and 6/93 (6.5%) reported full compliance with BHIVA and NICE guidance respectively. A uniform national guideline is required
The statistics of the entanglement changes generated by the Hadamard-CNOT quantum circuit
We consider the change of entanglement of formation produced by
the Hadamard-CNOT circuit on a general (pure or mixed) state describing
a system of two qubits. We study numerically the probabilities of obtaining
different values of , assuming that the initial state is randomly
distributed in the space of all states according to the product measure
recently introduced by Zyczkowski {\it et al.} [Phys. Rev. A {\bf 58} (1998)
883].Comment: 12 pages, 2 figure
Conditional q-Entropies and Quantum Separability: A Numerical Exploration
We revisit the relationship between quantum separability and the sign of the
relative q-entropies of composite quantum systems. The q-entropies depend on
the density matrix eigenvalues p_i through the quantity omega_q = sum_i p_i^q.
Renyi's and Tsallis' measures constitute particular instances of these
entropies. We perform a systematic numerical survey of the space of mixed
states of two-qubit systems in order to determine, as a function of the degree
of mixture, and for different values of the entropic parameter q, the volume in
state space occupied by those states characterized by positive values of the
relative entropy. Similar calculations are performed for qubit-qutrit systems
and for composite systems described by Hilbert spaces of larger dimensionality.
We pay particular attention to the limit case q --> infinity. Our numerical
results indicate that, as the dimensionalities of both subsystems increase,
composite quantum systems tend, as far as their relative q-entropies are
concerned, to behave in a classical way
Beneficial effect of NNRTI over boosted PI first line cART on CD4 T-cell restoration in older HIV-1+patients
Entanglement Distribution and Entangling Power of Quantum Gates
Quantum gates, that play a fundamental role in quantum computation and other
quantum information processes, are unitary evolution operators that
act on a composite system changing its entanglement. In the present
contribution we study some aspects of these entanglement changes. By recourse
of a Monte Carlo procedure, we compute the so called "entangling power" for
several paradigmatic quantum gates and discuss results concerning the action of
the CNOT gate. We pay special attention to the distribution of entanglement
among the several parties involved
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