111 research outputs found
A Configurable Protocol for Quantum Entanglement Distribution to End Nodes
The primary task of a quantum repeater network is to deliver entanglement
among end nodes. Most of existing entanglement distribution protocols do not
consider purification, which is thus delegated to an upper layer. This is a
major drawback since, once an end-to-end entangled connection (or a portion
thereof) is established it cannot be purified if its fidelity (F) does not fall
within an interval bounded by Fmin (greater than 0.5) and Fmax (less than 1).
In this paper, we propose the Ranked Entanglement Distribution Protocol
(REDiP), a connection-oriented protocol that overcomes the above drawback. This
result was achieved by including in our protocol two mechanisms for carrying
out jointly purification and entanglement swapping. We use simulations to
investigate the impact of these mechanisms on the performance of a repeater
network, in terms of throughput and fidelity. Moreover, we show how REDiP can
easily be configured to implement custom entanglement swapping and purification
strategies, including (but not restricted to) those adopted in two recent
works.Comment: 6 pages, 6 figures, submitted to IEEE ICC 202
Discriminating Quantum States in the Presence of a Deutschian CTC: A Simulation Analysis
In an article published in 2009, Brun et al. proved that in the presence of a “Deutschian” closed timelike curve, one can map distinct nonorthogonal states (hereafter, input set) to the standard orthonormal basis of a -dimensional state space. To implement this result, the authors proposed a quantum circuit that includes, among SWAP gates, a fixed set of controlled operators (boxes) and an algorithm for determining the unitary transformations carried out by such boxes. To our knowledge, what is still missing to complete the picture is an analysis evaluating the performance of the aforementioned circuit from an engineering perspective. The objective of this article is, therefore, to address this gap through an in-depth simulation analysis, which exploits the approach proposed by Brun et al. in 2017. This approach relies on multiple copies of an input state, multiple iterations of the circuit until a fixed point is (almost) reached. The performance analysis led us to a number of findings. First, the number of iterations is significantly high even if the number of states to be discriminated against is small, such as 2 or 3. Second, we envision that such a number may be shortened as there is plenty of room to improve the unitary transformation acting in the aforementioned controlled boxes. Third, we also revealed a relationship between the number of iterations required to get close to the fixed point and the Chernoff limit of the input set used: the higher the Chernoff bound, the smaller the number of iterations. A comparison, although partial, with another quantum circuit discriminating the nonorthogonal states, proposed by Nareddula et al. in 2018, is carried out and differences are highlighted
Nonviral gene-delivery by highly fluorinated gemini bispyridinium surfactant-based DNA nanoparticles
Biological and thermodynamic properties of a new homologous series of highly fluorinated bispyridinium
cationic gemini surfactants, differing in the length of the spacer bridging the pyridinium polar
heads in 1,10 position, are reported for the first time. Interestingly, gene delivery ability is closely
associated with the spacer length due to a structural change of the molecule in solution. This conformation
change is allowed when the spacer reaches the right length, and it is suggested by the trends
of the apparent and partial molar enthalpies vs molality. To assess the compounds’ biological activity,
they were tested with an agarose gel electrophoresis mobility shift assay (EMSA), MTT proliferation
assay and Transient Transfection assays on a human rhabdomyosarcoma cell line. Data from atomic
force microscopy (AFM) allow for morphological characterization of DNA nanoparticles. Dilution
enthalpies, measured at 298 K, enabled the determination of apparent and partial molar enthalpies
vs molality. All tested compounds (except that with the longest spacer), at different levels, can deliver
the plasmid when co-formulated with 1,2-dioleyl-sn-glycero-3-phosphoethanolamine (DOPE). The
compound with a spacer formed by eight carbon atoms gives rise to a gene delivery ability that is
comparable to that of the commercial reagent. The compound with the longest spacer compacts
DNA in loosely condensed structures by forming bows, which are not suitable for transfection.
Regarding the compounds’ hydrogenated counterparts, the tight relationship between the solutio
Histamine modulates spinal motoneurons and locomotor circuits
Spinal motoneurons and locomotor networks are regulated by monoamines, among which, the contribution of histamine has yet to be fully addressed. The present study investigates histaminergic regulation of spinal activity, combining intra- and extracellular electrophysiological recordings from neonatal rat spinal cord in vitro preparations. Histamine dose-dependently and reversibly generated motoneuron depolarization and action potential firing. Histamine (20ĂŽÂĽM) halved the area of dorsal root reflexes and always depolarized motoneurons. The majority of cells showed a transitory repolarization, while 37% showed a sustained depolarization maintained with intense firing. Extracellularly, histamine depolarized ventral roots (VRs), regardless of blockage of ionotropic glutamate receptors. Initial, transient glutamate-mediated bursting was synchronous among VRs, with some bouts of locomotor activity in a subgroup of preparations. After washout, the amplitude of spontaneous tonic discharges increased. No desensitization or tachyphylaxis appeared after long perfusion or serial applications of histamine. On the other hand, histamine induced single motoneuron and VR depolarization, even in the presence of tetrodotoxin (TTX). During chemically induced fictive locomotion (FL), histamine depolarized VRs. Histamine dose-dependently increased rhythm periodicity and reduced cycle amplitude until near suppression. This study demonstrates that histamine induces direct motoneuron membrane depolarization and modulation of locomotor output, indicating new potential targets for locomotor neurorehabilitation
Nutritional considerations during prolonged exposure to a confined, hyperbaric, hyperoxic environment: Recommendations for saturation divers
Saturation diving is an occupation that involves prolonged exposure to a confined, hyperoxic, hyperbaric environment. The unique and extreme environment is thought to result in disruption to physiological and metabolic homeostasis, which may impact human health and performance. Appropriate nutritional intake has the potential to alleviate and/or support many of these physiological and metabolic concerns, whilst enhancing health and performance in saturation divers. Therefore, the purpose of this review is to identify the physiological and practical challenges of saturation diving and consequently provide evidence-based nutritional recommendations for saturation divers to promote health and performance within this challenging environment. Saturation diving has a high-energy demand, with an energy intake of between 44 and 52 kcal/kg body mass per day recommended, dependent on intensity and duration of underwater activity. The macronutrient composition of dietary intake is in accordance with the current Institute of Medicine guidelines at 45-65 % and 20-35 % of total energy intake for carbohydrate and fat intake, respectively. A minimum daily protein intake of 1.3 g/kg body mass is recommended to facilitate body composition maintenance. Macronutrient intake between individuals should, however, be dictated by personal preference to support the attainment of an energy balance. A varied diet high in fruit and vegetables is highly recommended for the provision of sufficient micronutrients to support physiological processes, such as vitamin B12 and folate intake to facilitate red blood cell production. Antioxidants, such as vitamin C and E, are also recommended to reduce oxidised molecules, e.g. free radicals, whilst selenium and zinc intake may be beneficial to reinforce endogenous antioxidant reserves. In addition, tailored hydration and carbohydrate fueling strategies for underwater work are also advised
Encoding and extracting a classical Internet packet from a qubit: issues, algorithms and their performance evaluation
The Quantum Internet has been conceived as a disruptive communication paradigm
to transfer qubit states among different computers so as to support applications
which are out of reach for the current Internet. Using qubits to convey classical
internet packets (basically n-bit strings of classical information) through the
Quantum Internet is a challenging issue which is thoroughly investigated in the
thesis. An infinite amount of information can be encoded in the amplitudes of a
qubit. However this information cannot be accessed easily: when a qubit is
measured it collapses either on 0 or 1, losing everything that was stored inside.
Holevo’s theorem sets an upper bound, stating that only one classical bit of
information can be reliably extracted from a qubit and this looks pretty bad for our
purposes. The transmission of two bits via a single qubit is made possible by
the Superdense coding protocol. However the bit length of a packet is much higher
than 2!
The violation of the Holevo bound, and thus the retrieval of an n-bit string from a
single qubit, is made possible by the Deutschian closed timelike curve (D-CTC). In
this thesis we focus on an iterative algorithm to simulate the presence of a D-CTC
and extract n-bits of information from a qubit state. We evaluate the performances
of this algorithm and compare its outcomes with a theoretical limit, called the
Quantum Chernoff bound. The insights gained during the performance analysis allowed us to
formulate a number of coding proposals which outperform those of the assessed
algorithm
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