arXiv subjects

Pedro Orellana

Publications and source records attributed to Pedro Orellana.

9 recordsLinked to original sources

arXiv2026

Shot noise signatures of Majorana-assisted transport in an Aharonov-Bohm interferometer

In this work, we investigate the finite-bias charge current, shot noise, and Fano factor in an Aharonov-Bohm interferometer composed of two parallel quantum dots, each side-coupled to a topological superconducting nanowire represented by an effective Kitaev chain hosting Majorana bound states at its ends. The transport properties are calculated using the nonequilibrium Green's function formalism within the equation-of-motion approach. Our results show that coupling to the Majorana bound states significantly modifies the interference pattern, producing distinctive signatures in the current, shot noise, and Fano factor. These signatures are particularly pronounced at the half-flux condition, where destructive interference suppresses the conventional transport background and enhances the visibility of Majorana-assisted transport. These findings demonstrate that finite-bias shot-noise spectroscopy provides a sensitive indirect probe of Majorana bound states in hybrid superconducting-nanowire interferometers.

cond-mat.mes-hall↗

arXiv2026

Phase-controlled quasi-bound states in the continuum and thermoelectric enhancement in Majorana-quantum-dot nanostructures

We investigate how the interplay between Majorana zero modes (MZMs) and bound states in the continuum (BICs) governs the electronic thermoelectric response of a crossbar-shaped quantum dot (QD) coupled to two topological-superconductor nanowires. Using the Green-function formalism, exact linear-response energy integrals, and their low-temperature Sommerfeld expansion, we analyze the spectral and thermoelectric properties of the system. We show that symmetry breaking converts BICs into quasi-BICs, allowing them to contribute to electrical and thermal transport and thereby generate a finite thermoelectric response. While unequal nanowire lengths, reflected in different intra-Majorana coupling strengths, produce only a modest enhancement of $ZT_{el}$, detuning the QD level increases $ZT_{el}$ by approximately one order of magnitude. Superconducting-phase control produces a much stronger enhancement, reaching $ZT_{el} \simeq 0.75$ through a quadratic transmission zero and a pronounced violation of the Wiedemann-Franz law. The low-temperature values $ZT^{max}_{el} \simeq 0.755$ and $\mathscr{L} /\mathscr{L}_{0} = 21/5$ are universal consequences of this quadratic antiresonance. Our results establish phase-tunable thermoelectric signatures of the Majorana-coupled interference structure and identify superconducting-phase control as an efficient means of engineering the electronic response of topological hybrid nanostructures.

cond-mat.mes-hall↗

arXiv2026

Quantum Magic Reveals CP Phases Invisible to Entanglement in Spin-0 Decays

All standard scalar quantum-information measures -- concurrence, negativity, entanglement entropy, the optimized CHSH bound, and quantum Fisher information -- are CP-blind in ideal \\ spin-0 $\to f\bar f$ decays because the two-qubit spin state is maximally entangled for every CP angle. We show that stabilizer magic, fixed in the physical Pauli frame of spin analysis, escapes this blind spot: the stabilizer Rényi entropy admits an exact closed form, vanishing at CP-definite and Clifford phases and peaking at maximal non-Clifford mixing. Two experimentally accessible, magic-inspired CP witnesses follow; the linear amplitude is $14.3\times$ more efficient than its quartic counterpart and reaches discovery-level sensitivity at the HL-LHC for $H\toτ^+τ^-$.

quant-ph↗

arXiv2026

Geometric control of maximal entanglement via bound states in the continuum

Bound states in the continuum (BiCs) convert dissipative open systems into effectively closed quantum subspaces through destructive interference. We show that two identical giant atoms coupled to a one-dimensional waveguide support BICs that coincide with maximally entangled atomic states. Most importantly, entanglement is predominantly determined by the geometric design; the ratio of intra-atomic connection lengths fixes the concurrence, while the propagation phase between atoms selects a family of Bell-like states. We further analyze the dynamical stability of these maximally entangled BICs under exact time evolution, revealing a clear hierarchy of robustness against parameter perturbations. Our results establish an analytical bridge between symmetry, geometry, entanglement, and BICs in giant-atom waveguide platforms.

quant-ph↗

arXiv2025

Unconventional Floquet topological phases in the SSH lattice

Topological materials, known for their edge states robust against local perturbations, hold promise for next-generation quantum technologies, but remain scarce in nature and challenging to realize in static systems. The Su-Schrieffer-Heeger chain is a one-dimensional system for topological phases, although its static control is limited. To overcome these limitations, we propose to use high-frequency monochromatic driving and modulated amplitude pulses to dynamically induce and switch the Floquet topological phases. Using a Kramers-Henneberger-like transformation, we encode all Floquet sidebands into a single effective Hamiltonian. We demonstrate that both monochromatic and experimental pulse protocols (Gaussian and fast-beating envelopes) can induce topological edge states, enabling dynamic phase switching. Notably, fast-beating modulations require significantly lower field strengths than monochromatic ones, especially with larger inter-dimer separations. Our findings offer an experimentally feasible route for Floquet engineering, paving the way for ultrafast and energy efficient control of topological phases in quantum platforms, opening up new possibilities in the field of dynamic quantum materials.

quant-ph↗

arXiv2025

Thermoelectric transport through a Majorana zero modes interferometer

In this study, we examine the thermoelectric characteristics of a system consisting of two topological superconducting nanowires, each exhibiting Majorana zero modes at their ends, connected to leads within an interferometer configuration. By employing Green's function formalism, we derive the spectral properties and transport coefficients. Our findings indicate that bound states in the continuum (BICs) manifest in symmetric setups, influenced by the length of the wires and coupling parameters. Deviations of the magnetic flux from specific values transform BICs into quasi-BICs with finite width, resulting in conductance antiresonances. The existence and interplay of Majorana zero modes enhance thermoelectric performance in asymmetric configurations. Modulating the magnetic flux transitions BICs into quasi-BICs significantly enhances the Seebeck coefficient and figure of merit, thereby proposing a strategy for optimizing thermoelectric efficiency in systems based on Majorana zero modes.

cond-mat.mes-hall↗

arXiv2023

Bound states in the continuum in a fluxonium qutrit

The heavy fluxonium at zero external flux has a long-lived state when coupled capacitively to any other system. We analyze it by projecting all the fluxonium relevant operators into the qutrit subspace, as this long-lived configuration corresponds to the second excited fluxonium level. This state becomes a bound-state in the continuum (BIC) when the coupling occurs to an extended system supporting a continuum of modes. In the case without noise, we find BIC lifetimes that can be much larger than seconds $T_1\gg {\rm s}$ when the fluxonium is coupled to a superconducting waveguide, while typical device frequencies are in the order of ${\rm GHz}$. We have performed a detailed study of the different sources of decoherence in a realistic experiment, obtaining that upward transitions caused by a finite temperature in the waveguide and decay induced by $1/f$-flux noise are the most dangerous ones. Even in their presence, BICs decay times could reach the range of ${T_1\sim \rm 10^{-1} ms},$ while preparation times are of the order of $10^{2}$ns.

quant-ph↗

arXiv2013

Electronic transport of folded graphene nanoribbons

We investigate the electronic transport properties of a folded graphene nanoribbon with monolayer nanoribbon contacts. We consider two possible foldings: either the nanoribbon can be folded onto itself in the shape of a hairpin with the nanoribbon leads at a $0^\circ$ angle, or the monolayer contacts have different directions, forming a $60^\circ$ angle. The system is described by a single $π$-band nearest-neighbor tight-binding Hamiltonian taking into account curvature effects. We have found that for the case of a nanoribbon folded over itself the conductance oscillates from almost zero and a finite value depending on the coupling between contacts, whereas in the $60^\circ$ angle folding the conductance is only slightly perturbed, allowing for the connection of graphene nanoelectronic components in a variety of geometries.

cond-mat.mes-hall↗

arXiv2011

Transport properties of graphene quantum dots

In this work we present a theoretical study of transport properties of a double crossbar junction composed by segments of graphene ribbons with different widths forming a graphene quantum dot structure. The systems are described by a single-band tight binding Hamiltonian and the Green's function formalism using real space renormalization techniques. We show calculations of the local density of states, linear conductance and I-V characteristics. Our results depict a resonant behavior of the conductance in the quantum dot structures which can be controlled by changing geometrical parameters such as the nanoribbon segments widths and relative distance between them. By applying a gate voltage on determined regions of the structure, it is possible to modulate the transport response of the systems. We show that negative differential resistance can be obtained for low values of gate and bias voltages applied.

cond-mat.mes-hall↗