70 research outputs found
Unspeakable quantum information
No verbal explanation can indicate a direction in space or the orientation of
a coordinate system. Only material objects can do it. In this article we
consider the use of a set of spin-\half particles in an entangled state for
indicating a direction, or a hydrogen atom in a Rydberg state for transmitting
a Cartesian frame. Optimal strategies are derived for the emission and
detection of the quantum signals.Comment: to appear in "Quantum Theory: Reconsideration of Foundations", ed. by
A. Khrennikov; series ``Math. Modelling in Physics, Engineering and Cognitive
Sciences'' V\"axj\"o Univ. Press (2002) - requires sprocl.st
Weak limits for quantum random walks
We formulate and prove a general weak limit theorem for quantum random walks
in one and more dimensions. With denoting position at time , we show
that converges weakly as to a certain distribution which
is absolutely continuous and of bounded support. The proof is rigorous and
makes use of Fourier transform methods. This approach simplifies and extends
certain preceding derivations valid in one dimension that make use of
combinatorial and path integral methods
Transmission of a Cartesian Frame by a Quantum System
A single quantum system, such as a hydrogen atom, can transmit a Cartesian coordinate frame (three axes). For this it has to be prepared in a superposition of states belonging to different irreducible representations of the rotation group. The algorithm for decoding such a state is presented, and the fidelity of transmission is evaluated
Quantum Entropy and Special Relativity
We consider a single free spin-1/2 particle. The reduced density matrix for its spin is not covariant under Lorentz transformations. The spin entropy is not a relativistic scalar and has no invariant meaning
Audio-based anomaly detection on edge devices via self-supervision and spectral analysis
In real-world applications, audio surveillance is often performed by large models that can detect many types of anomalies. However, typical approaches are based on centralized solutions characterized by significant issues related to privacy and data transport costs. In addition, the large size of these models prevented a shift to contexts with limited resources, such as edge devices computing. In this work we propose conv-SPAD, a method for convolutional SPectral audio-based Anomaly Detection that takes advantage of common tools for spectral analysis and a simple autoencoder to learn the underlying condition of normality of real scenarios. Using audio data collected from real scenarios and artificially corrupted with anomalous sound events, we test the ability of the proposed model to learn normal conditions and detect anomalous events. It shows performances in line with larger models, often outperforming them. Moreover, the modelâs small size makes it usable in contexts with limited resources, such as edge devices hardware
A de Finetti Representation Theorem for Quantum Process Tomography
In quantum process tomography, it is possible to express the experimenter's
prior information as a sequence of quantum operations, i.e., trace-preserving
completely positive maps. In analogy to de Finetti's concept of exchangeability
for probability distributions, we give a definition of exchangeability for
sequences of quantum operations. We then state and prove a representation
theorem for such exchangeable sequences. The theorem leads to a simple
characterization of admissible priors for quantum process tomography and solves
to a Bayesian's satisfaction the problem of an unknown quantum operation.Comment: 10 page
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