Ramón Aguado
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View article: Fluxoid valve effect in full-shell nanowire Josephson junctions
Fluxoid valve effect in full-shell nanowire Josephson junctions Open
We introduce a new type of supercurrent valve based on full-shell nanowires. These hybrid wires consist of a semiconductor core fully wrapped in a thin superconductor shell and subjected to an axial magnetic field. Due to the tubular shape…
View article: Non-Hermitian Skin Effect and Electronic Nonlocal Transport
Non-Hermitian Skin Effect and Electronic Nonlocal Transport Open
Open quantum systems governed by non-Hermitian effective Hamiltonians exhibit unique phenomena, such as the non-Hermitian skin effect, where eigenstates localize at system boundaries. We investigate this effect in a Rashba nanowire coupled…
View article: Characterizing local Majorana properties using Andreev states
Characterizing local Majorana properties using Andreev states Open
We propose using Andreev bound states (ABS) as spectroscopic probes to characterize Majorana zero modes (MZMs) in quantum-dot based minimal Kitaev chains. Specifically, we show that tunneling conductance measurements with a superconducting…
View article: Single-shot parity readout of a minimal Kitaev chain
Single-shot parity readout of a minimal Kitaev chain Open
Protecting qubits from noise is essential for building reliable quantum computers. Topological qubits offer a route to this goal by encoding quantum information non-locally, using pairs of Majorana zero modes. These modes form a shared fer…
View article: Theory of superconducting proximity effect in hole-based hybrid semiconductor-superconductor devices
Theory of superconducting proximity effect in hole-based hybrid semiconductor-superconductor devices Open
Hybrid superconductor-semiconductor systems have received a great deal of attention in the last few years because of their potential for quantum engineering, including novel qubits and topological devices. The proximity effect, the process…
View article: Josephson effect and critical currents in trivial and topological full-shell hybrid nanowires
Josephson effect and critical currents in trivial and topological full-shell hybrid nanowires Open
We perform microscopic numerical simulations of the Josephson effect through short junctions between two full-shell hybrid nanowires, comprised of a semiconductor core fully wrapped by a thin superconductor shell, both in the trivial and t…
View article: Non-Hermitian minimal Kitaev chains
Non-Hermitian minimal Kitaev chains Open
Starting from a double quantum dot realization of a minimal Kitaev chain, we demonstrate that non-Hermiticity stabilizes the so-called poor man's Majorana zero modes in a region of parameter space that is much broader than in the Hermitian…
View article: Non-Hermitian minimal Kitaev chains
Non-Hermitian minimal Kitaev chains Open
Starting from a double quantum dot realization of a minimal Kitaev chain, we demonstrate that non-Hermiticity stabilizes the so-called poor man's Majorana zero modes in a region of parameter space that is much broader than in the Hermitian…
View article: Fluxoid valve effect in full-shell nanowire Josephson junctions
Fluxoid valve effect in full-shell nanowire Josephson junctions Open
We introduce a new type of supercurrent valve based on full-shell nanowires. These hybrid wires consist of a semiconductor core fully wrapped in a thin superconductor shell and subjected to an axial magnetic field. Due to the tubular shape…
View article: Interplay between Majorana and Shiba states in a minimal Kitaev chain coupled to a superconductor
Interplay between Majorana and Shiba states in a minimal Kitaev chain coupled to a superconductor Open
Two semiconducting quantum dots (QDs) coupled through a superconductor constitute a minimal realisation of a Kitaev chain with Majorana zero modes (MZMs). Such MZMs can be detected by e.g., tunneling conductance between each QD and normal …
View article: Absence of Majorana oscillations in finite-length full-shell hybrid nanowires
Absence of Majorana oscillations in finite-length full-shell hybrid nanowires Open
Majorana bound states (MBSs) located at the ends of a hybrid superconductor-semiconductor nanowire are only true zero modes if their characteristic localization length is much smaller than the nanowire length, $ξ_M\ll L$. Otherwise, their …
View article: Thermodynamics of Non-Hermitian Josephson junctions with exceptional points
Thermodynamics of Non-Hermitian Josephson junctions with exceptional points Open
We present an analytical formulation of the thermodynamics, free energy and entropy, of any generic Bogoliubov de Genes model which develops exceptional point (EP) bifurcations in its complex spectrum when coupled to reservoirs. We apply o…
View article: Subgap states in semiconductor-superconductor devices for quantum technologies: Andreev qubits and minimal Majorana chains
Subgap states in semiconductor-superconductor devices for quantum technologies: Andreev qubits and minimal Majorana chains Open
In recent years, experimental advances have made it possible to achieve an unprecedented degree of control over the properties of subgap bound states in hybrid nanoscale superconducting structures. This research has been driven by the prom…
View article: Phenomenology of Majorana zero modes in full-shell hybrid nanowires
Phenomenology of Majorana zero modes in full-shell hybrid nanowires Open
Full-shell nanowires have been proposed as an alternative nanowire design in the search of topological superconductivity and Majorana zero modes (MZMs). They are hybrid nanostructures consisting of a semiconductor core fully covered by a t…
View article: Flux-tunable supercurrent in full-shell nanowire Josephson junctions
Flux-tunable supercurrent in full-shell nanowire Josephson junctions Open
Full-shell nanowires formed by a semiconducting core fully wrapped by an epitaxial superconducting shell, have recently been introduced as promising hybrid quantum devices. Despite this, however, their properties when forming a Josephson j…
View article: Phenomenology of Majorana zero modes in full-shell hybrid nanowires
Phenomenology of Majorana zero modes in full-shell hybrid nanowires Open
Full-shell nanowires have been proposed as an alternative nanowire design in the search of topological superconductivity and Majorana zero modes (MZMs). They are hybrid nanostructures consisting of a semiconductor core fully covered by a t…
View article: Minimal Kitaev-transmon qubit based on double quantum dots
Minimal Kitaev-transmon qubit based on double quantum dots Open
Minimal Kitaev chains composed of two semiconducting quantum dots coupled via a grounded superconductor have emerged as a promising platform to realize and study Majorana bound states (MBSs). We propose a hybrid qubit based on a Josephson …
View article: Strong-coupling theory of quantum dot Josephson junctions: role of the residual quasiparticle
Strong-coupling theory of quantum dot Josephson junctions: role of the residual quasiparticle Open
We consider an interacting quantum dot strongly coupled to two superconducting leads in a Josephson junction geometry. By defining symmetry-adapted superpositions of states from the leads, we formulate an effective Hamiltonian for the stro…
View article: Majorana bound states in encapsulated bilayer graphene
Majorana bound states in encapsulated bilayer graphene Open
The search for robust topological superconductivity and Majorana bound states continues, exploring both one-dimensional (1D) systems such as semiconducting nanowires and two-dimensional (2D) platforms. In this work we study a 2D approach b…
View article: Direct manipulation of a superconducting spin qubit strongly coupled to a transmon qubit
Direct manipulation of a superconducting spin qubit strongly coupled to a transmon qubit Open
Spin qubits in semiconductors are currently one of the most promising architectures for quantum computing. However, they face challenges in realizing multi-qubit interactions over extended distances. Superconducting spin qubits provide a p…
View article: Spectroscopy of spin-split Andreev levels in a quantum dot with superconducting leads
Spectroscopy of spin-split Andreev levels in a quantum dot with superconducting leads Open
We use a hybrid superconductor-semiconductor transmon device to perform spectroscopy of a quantum dot Josephson junction tuned to be in a spin-1/2 ground state with an unpaired quasiparticle. Due to spin-orbit coupling, we resolve two flux…
View article: Singlet-Doublet Transitions of a Quantum Dot Josephson Junction Detected in a Transmon Circuit
Singlet-Doublet Transitions of a Quantum Dot Josephson Junction Detected in a Transmon Circuit Open
We realize a hybrid superconductor-semiconductor transmon device in which the Josephson effect is controlled by a gate-defined quantum dot in an InAs/Al nanowire. Microwave spectroscopy of the transmon's transition spectrum allows us to pr…
View article: Majorana-like Coulomb spectroscopy in the absence of zero bias peaks
Majorana-like Coulomb spectroscopy in the absence of zero bias peaks Open
Hybrid semiconductor-superconductor devices hold great promise for realizing topological quantum computing with Majorana zero modes (MZMs). However, multiple claims of Majorana detection, based on either tunneling or Coulomb blockade (CB) …
View article: Majorana bound states in encapsulated bilayer graphene
Majorana bound states in encapsulated bilayer graphene Open
The search for robust topological superconductivity and Majorana bound states continues, exploring both one-dimensional (1D) systems such as semiconducting nanowires and two-dimensional (2D) platforms. In this work we study a 2D approach b…
View article: Fluxoid-induced pairing suppression and near-zero modes in quantum dots coupled to full-shell nanowires
Fluxoid-induced pairing suppression and near-zero modes in quantum dots coupled to full-shell nanowires Open
We analyze the subgap excitations and phase diagram of a quantum dot (QD) coupled to a semiconducting nanowire fully wrapped by a superconducting (S) shell. We take into account how a Little-Parks (LP) pairing fluxoid (a winding in the S p…
View article: Vortex-induced pairing suppression and near-zero modes in quantum dots coupled to full-shell nanowires
Vortex-induced pairing suppression and near-zero modes in quantum dots coupled to full-shell nanowires Open
We analyze the subgap excitations and phase diagram of a quantum dot (QD) coupled to a semiconducting nanowire fully wrapped by a superconducting (S) shell. We take into account how a Little-Parks (LP) pairing vortex in the shell influence…
View article: Nontopological zero-bias peaks in full-shell nanowires induced by flux-tunable Andreev states
Nontopological zero-bias peaks in full-shell nanowires induced by flux-tunable Andreev states Open
A Majorana look-alike Most experimental claims of Majorana bound states, unusual quasiparticles that may become the cornerstone of topological quantum computing, rest on the observation of a persistent zero bias peak (ZBP) in tunneling spe…