The tensor product postulate of quantum mechanics states that the Hilbert space of a composite system is the tensor product of the components' Hilbert spaces. All current formalizations of quantum mechanics that do not contain this postulate contain some equivalent postulate or assumption (sometimes hidden). Here we give a natural definition of composite system as a set containing the...
We draw a picture of physical systems allowing us to recognize what is the thing we call ”time”. Elements of the picture are two non-interacting, entangled quantum systems: one acting as a clock, and the other one as the evolving system. The setting is based on the ”Page and Wootters mechanism”, with tools from Lie-Group and large-N quantum approaches. The theoretical framework, based on a...
We discuss a decoherence process due to quantum gravity effects. We assume a foamy quantum spacetime with a fluctuating minimal length coinciding on average with the Planck scale. Considering deformed canonical commutation relations with a fluctuating deformation parameter, we derive a Lindblad master equation that yields localization in energy space and decoherence times consistent with the...
We address the question whether a reversible transformation produces a causal influence from one of its input systems to one of its outputs. In quantum theory causal influence is typically identified with signalling. A second notion is borrowed from the theory of quantum cellular automata. We adopt an extension of the latter, in the context of general probabilistic theories. We show that in...
Non-abelian gauge fields emerge naturally in the description of adiabatically evolving quantum systems. In this talk we show that they also play a role in Thouless pumping in the presence of degenerate bands. Specifically, we consider a photonic Lieb lattice and show that when the lattice parameters are slowly modulated, the propagation of the photons bear the fingerprints of the underlying...
In a quantum network, entanglement between qubits located in remote nodes is a fundamental resource for different applications including distributed quantum computing and quantum repeaters. Once can generate entanglement between distant ions by creating an ion-photon entangled pair at each of the two network nodes, steering the photons to opposite ports of a beamsplitter, and subsequently...
