184 research outputs found
Entanglement witnesses for a class of bipartite states of n x n qubits
We characterize the positive maps detecting the entangled bipartite states of
n x n qubits that are diagonal with respect to the orthonormal basis
constructed by tensor products of Pauli matrices acting on the totally
symmetric state. We then discuss the case n=2 for a class of states completely
determined by the geometric patterns of subsets of a 16 point lattice.Comment: 25 page
Direct CP-violation as a test of quantum mechanics
Direct CP-violating effects in the neutral kaon system result in violations
of certain Bell-like inequalities. The new experimental results on the
determination of the phenomenological parameter epsilon' allow to dismiss a
large class of ``hidden variable'' alternatives to quantum mechanics.Comment: 15 pages, Te
On deciding whether a Boolean function is constant or not
We study the probability of making an error if, by querying an oracle a fixed
number of times, we declare constant a randomly chosen n-bit
Boolean function. We compare the classical and the quantum case, and we
determine for how many oracle-queries k and for how many bits n one querying
procedure is more efficient than the other.Comment: 8 pages, Latex, 5 figures; accepted for publication on International
Journal of Quantum Informatio
Translation Invariant States on Twisted Algebras on a Lattice
We construct an algebra with twisted commutation relations and equip it with
the shift. For appropriate irregularity of the non-local commutation relations
we prove that the tracial state is the only translation-invariant state
On Some Hamiltonian Models of Brownian Motion
The Langevin and Fokker-Planck structures of two phase-space gaussian Markov processes are investigated in terms of their algebraic properties
The Classical Limit of a Class of Quantum Dynamical Semigroups
The Ghirardi-Rimini-Weber (G.R.W.-) model is studied in the limit ħ â 0 and it is shown that a weak-coupling limit is needed in order to retain its dissipative character at the phase-space level. As a byproduct, solutions of the corresponding Chapman-Kolmogorov differential equation, with linear Liouville term, are provided explicitly
Non-markovian mesoscopic dissipative dynamics of open quantum spin chains
We study the dissipative dynamics of quantum spins with Lindblad
generator consisting of operators scaling as fluctuations, namely with the
inverse square-root of . In the large limit, the microscopic dissipative
time-evolution converges to a non-Markovian unitary dynamics on strictly local
operators, while at the mesoscopic level of fluctuations it gives rise to a
dissipative non-Markovian dynamics. The mesoscopic time-evolution is Gaussian
and exhibits either a stable or an unstable asymptotic character; furthermore,
the mesoscopic dynamics builds correlations among fluctuations that survive in
time even when the original microscopic dynamics is unable to correlate local
observables.Comment: 18 page
PULP-HD: Accelerating Brain-Inspired High-Dimensional Computing on a Parallel Ultra-Low Power Platform
Computing with high-dimensional (HD) vectors, also referred to as
, is a brain-inspired alternative to computing with
scalars. Key properties of HD computing include a well-defined set of
arithmetic operations on hypervectors, generality, scalability, robustness,
fast learning, and ubiquitous parallel operations. HD computing is about
manipulating and comparing large patterns-binary hypervectors with 10,000
dimensions-making its efficient realization on minimalistic ultra-low-power
platforms challenging. This paper describes HD computing's acceleration and its
optimization of memory accesses and operations on a silicon prototype of the
PULPv3 4-core platform (1.5mm, 2mW), surpassing the state-of-the-art
classification accuracy (on average 92.4%) with simultaneous 3.7
end-to-end speed-up and 2 energy saving compared to its single-core
execution. We further explore the scalability of our accelerator by increasing
the number of inputs and classification window on a new generation of the PULP
architecture featuring bit-manipulation instruction extensions and larger
number of 8 cores. These together enable a near ideal speed-up of 18.4
compared to the single-core PULPv3
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