4,079 research outputs found
Multicasting Homogeneous and Heterogeneous Quantum States in Quantum Networks
In this paper, we target the practical implementation issues of quantum
multicast networks. First, we design a recursive lossless compression that
allows us to control the trade-off between the circuit complexity and the
dimension of the compressed quantum state. We give a formula that describes the
trade-off, and further analyze how the formula is affected by the controlling
parameter of the recursive procedure. Our recursive lossless compression can be
applied in a quantum multicast network where the source outputs homogeneous
quantum states (many copies of a quantum state) to a set of destinations
through a bottleneck. Such a recursive lossless compression is extremely useful
in the current situation where the technology of producing large-scale quantum
circuits is limited. Second, we develop two lossless compression schemes that
work for heterogeneous quantum states (many copies of a set of quantum states)
when the set of quantum states satisfies a certain structure. The heterogeneous
compression schemes provide extra compressing power over the homogeneous
compression scheme. Finally, we realize our heterogeneous compression schemes
in several quantum multicast networks, including the single-source
multi-terminal model, the multi-source multi-terminal model, and the ring
networks. We then analyze the bandwidth requirements for these network models.Comment: 24 pages, 9 figure
Origin of Borromean systems
The complex energies of the three-body resonances for one infinitely heavy
particle and two non-interacting light particles are the sum of the two
contributing two-body complex resonance energies. The bound state of a
Borromean system originates from a resonance when the third interaction is
introduced, a finite mass is allowed and proper angular momentum coupling is
included. The relative importance of these contributions are investigated and
the resulting structure of Borromean systems are traced back to the two-body
continuum properties. The and states in He result from
neutron-core p-states and the ground and first excited state of Li
originate from neutron-core and -states.Comment: Physics Letters B, in pres
An open--quantum--system formulation of particle decay
We consider an open quantum system which contains unstable states. The time
evolution of the system can be described by an effective non-hermitian
Hamiltonian H_{eff}, in accord with the Wigner--Weisskopf approximation, and an
additional term of the Lindblad form, the socalled dissipator. We show that,
after enlarging the original Hilbert space by states which represent the decay
products of the unstable states, the non-hermitian part of H_{eff} --the
``particle decay''-- can be incorporated into the dissipator of the enlarged
space via a specific Lindblad operator. Thus the new formulation of the time
evolution on the enlarged space has a hermitian Hamiltonian and is probability
conserving. The equivalence of the new formulation with the original one
demonstrates that the time evolution which is governed by a non-hermitian
Hamiltonian and a dissipator of the Lindblad form is nevertheless completely
positive, just as systems with hermitian Hamiltonians.Comment: 8 page
Magnesium for the management of chronic noncancer pain in adults:Protocol for a Systematic Review
International audienc
Origin of three-body resonances
We expose the relation between the properties of the three-body continuum
states and their two-body subsystems. These properties refer to their bound and
virtual states and resonances, all defined as poles of the -matrix. For one
infinitely heavy core and two non-interacting light particles, the complex
energies of the three-body poles are the sum of the two two-body complex
pole-energies. These generic relations are modified by center-of-mass effects
which alone can produce a Borromean system. We show how the three-body states
evolve in He, Li, and Be when the nucleon-nucleon interaction is
continuously switched on. The schematic model is able to reproduce the main
properties in their spectra. Realistic calculations for these nuclei are shown
in detail for comparison. The implications of a core with non-zero spin are
investigated and illustrated for Ne (O+p+p). Dimensionless units
allow predictions for systems of different scales.Comment: 15 pages, 7 figure
Odour conditioning of positive affective states: Rats can learn to associate an odour with being tickled.
Most associative learning tests in rodents use negative stimuli, such as electric shocks. We
investigated if young rats can learn to associate the presence of an odour with the experience of being tickled (i.e. using an experimenter’s hand to mimic rough-and-tumble play),
shown to elicit 50 kHz ultrasonic vocalisations (USVs), which are indicative of positive affect.
Male, pair-housed Wistar rats (N = 24) were all exposed to two neutral odours (A and B) presented in a perforated container on alternate days in a test arena. Following 60s of exposure, the rats were either tickled on days when odour A (n = 8) or odour B (n = 8) was
present, or never tickled (n = 8). When tickled, rats produced significantly more 50 kHz
USVs compared to the days when not being tickled, and compared to control rats. The level
of anticipatory 50 kHz USVs in the 60s prior to tickling did not differ significantly between the
tickled and control rats. As a retrieval test following the odour conditioning, rats were
exposed successively in the same arena to three odours: an unknown neutral odour, extract
of fox faeces, and either odours A or B. Compared to controls, 50 kHz USVs of tickled rats
increased when exposed to the odour they had previously experienced when tickled, indicating that these rats had learned to associate the odour with the positive experience of
being tickled. In a test with free access for 5 min to both arms of a T-maze, each containing
one of the odours, rats tickled with odour A spent more time in the arm with this odour. This
work is the first to test in a fully balanced design whether rats can learn to associate an
odour with tickling, and indicates that positive odour conditioning has potential to be used as
an alternative to negative conditioning tests
Ancilla-based quantum simulation
We consider simulating the BCS Hamiltonian, a model of low temperature
superconductivity, on a quantum computer. In particular we consider conducting
the simulation on the qubus quantum computer, which uses a continuous variable
ancilla to generate interactions between qubits. We demonstrate an O(N^3)
improvement over previous work conducted on an NMR computer [PRL 89 057904
(2002) & PRL 97 050504 (2006)] for the nearest neighbour and completely general
cases. We then go on to show methods to minimise the number of operations
needed per time step using the qubus in three cases; a completely general case,
a case of exponentially decaying interactions and the case of fixed range
interactions. We make these results controlled on an ancilla qubit so that we
can apply the phase estimation algorithm, and hence show that when N \geq 5,
our qubus simulation requires significantly less operations that a similar
simulation conducted on an NMR computer.Comment: 20 pages, 10 figures: V2 added section on phase estimation and
performing controlled unitaries, V3 corrected minor typo
Numerical simulation of electrocardiograms for full cardiac cycles in healthy and pathological conditions
This work is dedicated to the simulation of full cycles of the electrical
activity of the heart and the corresponding body surface potential. The model
is based on a realistic torso and heart anatomy, including ventricles and
atria. One of the specificities of our approach is to model the atria as a
surface, which is the kind of data typically provided by medical imaging for
thin volumes. The bidomain equations are considered in their usual formulation
in the ventricles, and in a surface formulation on the atria. Two ionic models
are used: the Courtemanche-Ramirez-Nattel model on the atria, and the "Minimal
model for human Ventricular action potentials" (MV) by Bueno-Orovio, Cherry and
Fenton in the ventricles. The heart is weakly coupled to the torso by a Robin
boundary condition based on a resistor- capacitor transmission condition.
Various ECGs are simulated in healthy and pathological conditions (left and
right bundle branch blocks, Bachmann's bundle block, Wolff-Parkinson-White
syndrome). To assess the numerical ECGs, we use several qualitative and
quantitative criteria found in the medical literature. Our simulator can also
be used to generate the signals measured by a vest of electrodes. This
capability is illustrated at the end of the article
Device-independent certification of entangled measurements
We present a device-independent protocol to test if a given black-box
measurement device is entangled, that is, has entangled eigenstates. Our scheme
involves three parties and is inspired by entanglement swapping; the test uses
the Clauser-Horne-Shimony-Holt (CHSH) Bell inequality, checked between each
pair of parties. Also, focusing on the case where all particles are qubits, we
characterize quantitatively the deviation of the measurement device from a
perfect Bell state measurement.Comment: 5 pages, 2 figure
Open/Closed Duality, Unstable D-Branes, and Coarse-Grained Closed Strings
At the final stage of unstable D-brane decay in the effective field theory
approach, all energy and momentum of the initial state are taken up by two
types of fluids, known as string fluid and tachyon matter. In this note, we
compare motion of this fluid system to that of macroscopic collection of
stretched closed strings and find a precise match at classical level. The
string fluid reflects low frequency undulation of the stretched strings while
the tachyon matter encodes the average effect of high frequency oscillations
turned on those strings. In particular, the combined fluid system has been
known to have a reduced speed of light, depending on the composition, and we
show that this property is exactly reproduced in classical motion on the closed
string side. Finally we illustrate how the tachyon matter may be viewed as an
effective degrees of freedom carrying high frequency energy-momentum of
Nambu-Goto strings by coarse-graining the dynamics of the latter.Comment: LaTeX, 29 pages, 4 figure file
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