2,329 research outputs found
Non-divisibility vs backflow of information in understanding revivals of quantum correlations for continuous-variable systems interacting with fluctuating environments
We address the dynamics of quantum correlations for a bipartite
continuous-variable quantum system interacting with its fluctuating
environment. In particular, we consider two independent quantum oscillators
initially prepared in a Gaussian state, e.g. a squeezed thermal state, and
compare the dynamics resulting from local noise, i.e. oscillators coupled to
two independent external fields, to that originating from common noise, i.e.
oscillators interacting with a single common field. We prove non-Markovianity
(non-divisibility) of the dynamics in both regimes and analyze the connections
between non-divisibility, backflow of information and revivals of quantum
correlations. Our main results may be summarized as follows: (i) revivals of
quantumness are present in both scenarios, however, the interaction with a
common environment better preserves the quantum features of the system; (ii)
the dynamics is always non-divisible but revivals of quantum correlations are
present only when backflow of information is present as well. We conclude that
non-divisibility in its own is not a resource to preserve quantum correlations
in our system, i.e. it is not sufficient to observe recoherence phenomena.
Rather, it represents a necessary prerequisite to obtain backflow of
information, which is the true ingredient to obtain revivals of quantumness
Entanglement as a resource for discrimination of classical environments
We address extended systems interacting with classical fluctuating
environments and analyze the use of quantum probes to discriminate local noise,
described by independent fluctuating fields, from common noise, corresponding
to the interaction with a common one. In particular, we consider a bipartite
system made of two non interacting harmonic oscillators and assess
discrimination strategies based on homodyne detection, comparing their
performances with the ultimate bounds on the error probabilities of
quantum-limited measurements. We analyze in details the use of Gaussian probes,
with emphasis on experimentally friendly signals. Our results show that a joint
measurement of the position-quadrature on the two oscillators outperforms any
other homodyne-based scheme for any input Gaussian state
Assessment of landfill leachate biodegradability and treatability by means of allochthonous and autochthonous biomasses
The biodegradability and treatability of a young (3 years old) municipal landfill leachate was evaluated by means of chemical oxygen demand (COD) fractionation tests, based on respirometric techniques. The tests were performed using two different biomasses: one cultivated from the raw leachate (autochthonous biomass) and the other collected from a conventional municipal wastewater treatment plant after its acclimation to leachate (allochthonous biomass). The long term performances of the two biomasses were also studied. The results demonstrated that the amount of biodegradable COD in the leachate was strictly dependent on the biomass that was used to perform the fractionation tests. Using the autochthonous biomass, the amount of biodegradable organic substrate resulted in approximately 75% of the total COD, whereas it was close to 40% in the case of the allochthonous biomass, indicating the capacity of the autochthonous biomass to degrade a higher amount of organic compounds present in the leachate. The autochthonous biomass was characterized by higher biological activity and heterotrophic active fraction (14% vs 7%), whereas the activity of the allochthonous biomass was significantly affected by inhibitory compounds in the leachate, resulting in a lower respiration rate (SOUR = 13 mg O2 gVSS-1 h-1 vs 37 mg O2 gVSS-1 h-1). The long-term performance of the autochthonous and allochthonous biomasses indicated that the former was more suitable for the treatment of raw landfill leachate, ensuring higher removal performance towards the organic pollutants
Missense mutations in the perforin (PRF1) gene as a cause of hereditary cancer predisposition
Perforin, a pore-forming toxin released from secretory granules of NK cells and CTLs, is essential for their cytotoxic activity against infected or cancerous target cells. Bi-allelic loss-of-function mutations in the perforin gene are invariably associated with a fatal immunoregulatory disorder, familial haemophagocytic lymphohistiocytosis type 2 (FHL2), in infants. More recently, it has also been recognized that partial loss of perforin function can cause disease in later life, including delayed onset FHL2 and haematological malignancies. Herein we report a family in which a wide range of systemic inflammatory and neoplastic manifestations have occurred across three generations. We found that disease was linked to two missense perforin gene mutations (encoding A91V, R410W) that cause protein misfolding and partial loss of activity. These cases link the partial loss of perforin function with some solid tumours that are known to be controlled by the immune system, as well as haematological cancers. Our findings also demonstrate that perforin gene mutations can contribute to hereditary cancer predisposition
Quantum spatial correlations in high-gain parametric down-conversion measured by means of a CCD camera
We consider travelling-wave parametric down-conversion in the high-gain
regime and present the experimental demonstration of the quantum character of
the spatial fluctuations in the system. In addition to showing the presence of
sub-shot noise fluctuations in the intensity difference, we demonstrate that
the peak value of the normalized spatial correlations between signal and idler
lies well above the line marking the boundary between the classical and the
quantum domain. This effect is equivalent to the apparent violation of the
Cauchy-Schwartz inequality, predicted by some of us years ago, which represents
a spatial analogue of photon antibunching in time. Finally, we analyse
numerically the transition from the quantum to the classical regime when the
gain is increased and we emphasize the role of the inaccuracy in the
determination of the symmetry center of the signal/idler pattern in the
far-field plane.Comment: 21 pages, 11 figures, submitted to J. Mod. Opt. special issue on
Quantum Imagin
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