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Papers by Sara Di Martino

Research paper thumbnail of Dynamics of a particle confined in a two-dimensional dilating and deforming domain

Research paper thumbnail of Spatial separation and entanglement of identical particles

International Journal of Quantum Information, 2014

We reconsider the effect of indistinguishability on the reduced density operator of the internal ... more We reconsider the effect of indistinguishability on the reduced density operator of the internal degrees of freedom (tracing out the spatial degrees of freedom) for a quantum system composed of identical particles located in different spatial regions. We explicitly show that if the spin measurements are performed in disjoint spatial regions then there are no constraints on the structure of the reduced state of the system. This implies that the statistics of identical particles has no role from the point of view of separability and entanglement when the measurements are spatially separated. We extend the treatment to the case of n particles and show the connection with some recent criteria for separability based on subalgebras of observables.

Research paper thumbnail of Strong Monogamy Conjecture for Multiqubit Entanglement: The Four-Qubit Case

Physical Review Letters, 2014

We investigate the distribution of bipartite and multipartite entanglement in multiqubit states. ... more We investigate the distribution of bipartite and multipartite entanglement in multiqubit states. In particular, we define a set of monogamy inequalities sharpening the conventional Coffman-Kundu-Wootters constraints, and we provide analytical proofs of their validity for relevant classes of states. We present extensive numerical evidence validating the conjectured strong monogamy inequalities for arbitrary pure states of four qubits.

Research paper thumbnail of Quantum systems with time-dependent boundaries

International Journal of Geometric Methods in Modern Physics, 2015

We present here a set of lecture notes on quantum systems with time-dependent boundaries. In part... more We present here a set of lecture notes on quantum systems with time-dependent boundaries. In particular, we analyze the dynamics of a non-relativistic particle in a bounded domain of physical space, when the boundaries are moving or changing. In all cases, unitarity is preserved and the change of boundaries does not introduce any decoherence in the system.

Research paper thumbnail of An algebraic approach to the study of multipartite entanglement

Journal of Russian Laser Research

A simple algebraic approach to the study of multipartite entanglement for pure states is introduc... more A simple algebraic approach to the study of multipartite entanglement for pure states is introduced together with a class of suitable functionals able to detect entanglement. On this basis, some known results are reproduced. Indeed, by investigating the properties of the introduced functionals, it is shown that a subset of such class is strictly connected to the purity. Moreover, a direct and basic solution to the problem of the simultaneous maximization of three appropriate functionals for three-qubit states is provided, confirming that the simultaneous maximization of the entanglement for all possible bipartitions is compatible only with the structure of GHZ-states.

Research paper thumbnail of Dynamics of a particle confined in a two- or three-dimensional moving domain

The behavior of a quantum particle confined in a two-dimensional box whose walls are moving is in... more The behavior of a quantum particle confined in a two-dimensional box whose walls are moving is investigated and the relevant mathematical problem with moving boundaries is recast in the form of a problem with fixed boundaries and time-dependent Hamiltonian. Changes of the shape of the box are shown to be important, as it clearly emerges from the comparison between the 'pantographic' case (same shape of the box through all the process) and the case with deformation. Extension of the results to the three-dimensional case is also briefly discussed.

Research paper thumbnail of Quantum particle in a box with moving walls

Journal of Mathematical Physics, 1993

We analyze the non-relativistic problem of a quantum particle that bounces back and forth between... more We analyze the non-relativistic problem of a quantum particle that bounces back and forth between two moving walls. We recast this problem into the equivalent one of a quantum particle in a fixed box whose dynamics is governed by an appropriate time-dependent Schrödinger operator.

Research paper thumbnail of A quantum particle in a box with moving walls

We analyze the non-relativistic problem of a quantum particle that bounces back and forth between... more We analyze the non-relativistic problem of a quantum particle that bounces back and forth between two moving walls. We recast this problem into the equivalent one of a quantum particle in a fixed box whose dynamics is governed by an appropriate time-dependent Schroedinger operator.

Research paper thumbnail of Dynamics of a particle confined in a two-dimensional dilating and deforming domain

Research paper thumbnail of Spatial separation and entanglement of identical particles

International Journal of Quantum Information, 2014

We reconsider the effect of indistinguishability on the reduced density operator of the internal ... more We reconsider the effect of indistinguishability on the reduced density operator of the internal degrees of freedom (tracing out the spatial degrees of freedom) for a quantum system composed of identical particles located in different spatial regions. We explicitly show that if the spin measurements are performed in disjoint spatial regions then there are no constraints on the structure of the reduced state of the system. This implies that the statistics of identical particles has no role from the point of view of separability and entanglement when the measurements are spatially separated. We extend the treatment to the case of n particles and show the connection with some recent criteria for separability based on subalgebras of observables.

Research paper thumbnail of Strong Monogamy Conjecture for Multiqubit Entanglement: The Four-Qubit Case

Physical Review Letters, 2014

We investigate the distribution of bipartite and multipartite entanglement in multiqubit states. ... more We investigate the distribution of bipartite and multipartite entanglement in multiqubit states. In particular, we define a set of monogamy inequalities sharpening the conventional Coffman-Kundu-Wootters constraints, and we provide analytical proofs of their validity for relevant classes of states. We present extensive numerical evidence validating the conjectured strong monogamy inequalities for arbitrary pure states of four qubits.

Research paper thumbnail of Quantum systems with time-dependent boundaries

International Journal of Geometric Methods in Modern Physics, 2015

We present here a set of lecture notes on quantum systems with time-dependent boundaries. In part... more We present here a set of lecture notes on quantum systems with time-dependent boundaries. In particular, we analyze the dynamics of a non-relativistic particle in a bounded domain of physical space, when the boundaries are moving or changing. In all cases, unitarity is preserved and the change of boundaries does not introduce any decoherence in the system.

Research paper thumbnail of An algebraic approach to the study of multipartite entanglement

Journal of Russian Laser Research

A simple algebraic approach to the study of multipartite entanglement for pure states is introduc... more A simple algebraic approach to the study of multipartite entanglement for pure states is introduced together with a class of suitable functionals able to detect entanglement. On this basis, some known results are reproduced. Indeed, by investigating the properties of the introduced functionals, it is shown that a subset of such class is strictly connected to the purity. Moreover, a direct and basic solution to the problem of the simultaneous maximization of three appropriate functionals for three-qubit states is provided, confirming that the simultaneous maximization of the entanglement for all possible bipartitions is compatible only with the structure of GHZ-states.

Research paper thumbnail of Dynamics of a particle confined in a two- or three-dimensional moving domain

The behavior of a quantum particle confined in a two-dimensional box whose walls are moving is in... more The behavior of a quantum particle confined in a two-dimensional box whose walls are moving is investigated and the relevant mathematical problem with moving boundaries is recast in the form of a problem with fixed boundaries and time-dependent Hamiltonian. Changes of the shape of the box are shown to be important, as it clearly emerges from the comparison between the 'pantographic' case (same shape of the box through all the process) and the case with deformation. Extension of the results to the three-dimensional case is also briefly discussed.

Research paper thumbnail of Quantum particle in a box with moving walls

Journal of Mathematical Physics, 1993

We analyze the non-relativistic problem of a quantum particle that bounces back and forth between... more We analyze the non-relativistic problem of a quantum particle that bounces back and forth between two moving walls. We recast this problem into the equivalent one of a quantum particle in a fixed box whose dynamics is governed by an appropriate time-dependent Schrödinger operator.

Research paper thumbnail of A quantum particle in a box with moving walls

We analyze the non-relativistic problem of a quantum particle that bounces back and forth between... more We analyze the non-relativistic problem of a quantum particle that bounces back and forth between two moving walls. We recast this problem into the equivalent one of a quantum particle in a fixed box whose dynamics is governed by an appropriate time-dependent Schroedinger operator.