1,720,993 research outputs found
Charge transfer and coherence dynamics of tunnelling system coupled to a harmonic oscillator
No full textIrreversible Work versus Fidelity Susceptibility for infinitesimal quenches
No full textWe compare the irreversible work produced in an infinitesimal sudden quench
of a quantum system at zero temperature with its ground state fidelity
susceptibility, giving an explicit relation between the two quantities. We find
that the former is proportional to the latter but for an extra term appearing
in the irreversible work which includes also contributions from the excited
states. We calculate explicitly the two quantities in the case of the quantum
Ising chain, showing that at criticality they exhibit different scaling
behavior. The irreversible work, rescaled by square of the quench's amplitude,
exhibits a divergence slower than the fidelity susceptibility one. As a
consequence, the two quantities obey also different finite-size scaling
relations
A density matrix approach to the dynamical properties of a two-site Holstein model
No full textThe two-site Holstein model represents a first non-trivial paradigm for the interaction between an itinerant charge with a quantum oscillator, a very common topic in different ambits. Exact results can be achieved both analytically and numerically, nevertheless it can be useful to compare them with approximate, semi-classical techniques in order to highlight the role of quantum effects. In this paper we consider the adiabatic limit in which the oscillator is slower than the electron. A density matrix approach is introduced for studying the charge dynamics and the exact results are compared with two different approximations: a Born-Oppenheimer-based Static Approximation for the oscillator (SA) and a Quantum-classical (QC) dynamics
Strange correlators for topological quantum systems from bulk-boundary correspondence
Full text link“Strange” correlators provide a tool to detect topological phases arising in many-body models by computing the matrix elements of suitably defined two-point correlations between the states under investigation and trivial reference states. Their effectiveness depends on the choice of the adopted operators. In this paper, we give a systematic procedure for this choice, discussing the advantages of choosing operators using the bulk-boundary correspondence of the systems under scrutiny. Via the scaling exponents, we directly relate the algebraic decay of the strange correlators with the scaling dimensions of gapless edge modes operators. We begin our analysis with lattice models hosting symmetry-protected topological phases and we analyze the sums of the strange correlators, pointing out that integrating their moduli substantially reduces cancellations and finite-size effects. We also analyze instances of systems hosting intrinsic topological order, as well as strange correlators between states with different nontrivial topologies. Our results for both translational and nontranslational invariant cases, and in the presence of on-site disorder and long-range couplings, extend the validity of the strange correlator approach for the diagnosis of topological phases of matter and indicate a general procedure for their optimal choice
Strange correlators for topological quantum systems from bulk-boundary correspondence
No full text"Strange"correlators provide a tool to detect topological phases arising in many-body models by computing the matrix elements of suitably defined two-point correlations between the states under investigation and trivial reference states. Their effectiveness depends on the choice of the adopted operators. In this paper, we give a systematic procedure for this choice, discussing the advantages of choosing operators using the bulk-boundary correspondence of the systems under scrutiny. Via the scaling exponents, we directly relate the algebraic decay of the strange correlators with the scaling dimensions of gapless edge modes operators. We begin our analysis with lattice models hosting symmetry-protected topological phases and we analyze the sums of the strange correlators, pointing out that integrating their moduli substantially reduces cancellations and finite-size effects. We also analyze instances of systems hosting intrinsic topological order, as well as strange correlators between states with different nontrivial topologies. Our results for both translational and nontranslational invariant cases, and in the presence of on-site disorder and long-range couplings, extend the validity of the strange correlator approach for the diagnosis of topological phases of matter and indicate a general procedure for their optimal choice
Current transport properties and phase diagram of a Kitaev chain with long-range pairing
No full textWe describe a method to probe the quantum phase transition between the short-range topological phase and the long-range topological phase in the superconducting Kitaev chain with long-range pairing, both exhibiting subgap modes localized at the edges. The method relies on the effects of the finite mass of the subgap edge modes in the long-range regime (which survives in the thermodynamic limit) on the single-particle scattering coefficients through the chain connected to two normal leads
Observation of the Quantum Zeno Effect on a NISQ Device
Full text linkWe study the Quantum Zeno Effect (QZE) on a single qubit on IBM Quantum
Experience devices under the effect of multiple measurements. We consider two
possible cases: the Rabi evolution and the free decay. SPAM error mitigations
have also been applied. In both cases we observe the occurrence of the QZE as
an increasing of the survival probability with the number of measurements
Teleportation on a quantum dot array
No full textWe present a model of quantum teleportation protocol based on a double quantum dot array. The unknown qubit is encoded using a pair of quantum dots, with one excess electron, coupled by tunneling. It is shown how to create a maximally entangled state using an adiabatically increasing Coulomb repulsion between different dot pairs. This entangled state is exploited to perform teleportation again using an adiabatic coupling between itself and the incoming unknown state. Finally, a sudden separation of Bob's qubit allows a time evolution of Alice's which amounts to a modified version of standard Bell measurement. A transmission over a long distance could be obtained by considering the entangled state of a chain of N coupled double quantum dots. The system is shown to be increasingly robust with N against decoherence due to phonons
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