arXiv subjects

Monica Benito

Publications and source records attributed to Monica Benito.

4 recordsLinked to original sources

arXiv2026

Fast coherent control of a charge qubit on solid neon with a spin-qubit-compatible resonator

Electrons floating in vacuum provide a clean platform for quantum information processing owing to their isolation from material defects. In particular, electrons on solid neon have emerged as a promising qubit platform because of their potentially long coherence times. Here, toward spin-qubit realization, we couple a single electron on solid neon to a magnetic-field-compatible superconducting NbTiN nanowire resonator. We realize a charge qubit and demonstrate microwave readout and coherent control, with Rabi frequencies up to 76 MHz, an order of magnitude larger than in previous studies. Under strong driving, we observe a qubit frequency shift from nonlinear interactions with the intense microwave field. Deterministic electron trapping at an intended position remains challenging due to solid neon surface roughness; we characterize the electron's position from its differential coupling to distinct electrodes. Although not trapped at an intended position, our estimates indicate that spin-qubit demonstrations remain feasible.

cond-mat.mes-hall↗

arXiv2026

Modeling of flopping-mode spin qubits: beyond the two-site model

We present a flexible modeling framework for flopping-mode spin qubits that captures the spatial structure of the double-well confinement and magnetic-field-gradient profile going beyond conventional low-energy descriptions. By using this approach, we simulate electric dipole spin resonance-based single-qubit control and evaluate the frequency and spectral purity of the Rabi oscillations across different parameter regimes. Our analysis reveals a fundamental tradeoff between fast electrical driving and clean single-mode Rabi oscillations, and demonstrates that the standard two-site low-energy approximation can overestimate the Rabi frequency by up to $\sim$ 20\% in certain parameter regimes. We also investigate two-qubit control by considering two capacitively coupled flopping-mode qubits and derive the corresponding exchange interaction with an appropriately restricted configuration interaction treatment. Our approach reveals the interplay between the spatial profile of the double-well confinement, magnetic field gradient, and Coulomb interaction, which together govern the effective exchange coupling strength. Our spatially resolved modelling framework enables efficient exploration of double-well confinement parameters and magnetic field gradient profiles, enabling a transparent mapping from spatial device properties to flopping-mode qubit parameters and quality metrics.

cond-mat.mes-hall↗

arXiv2024

Electrical readout of spins in the absence of spin blockade

In semiconductor nanostructures, spin blockade (SB) is the most scalable mechanism for electrical spin readout, requiring only two bound spins for its implementation. In conjunction with charge sensing techniques, SB has led to high-fidelity readout of spins in semiconductor-based quantum processors. However, various mechanisms may lift SB, such as strong spin-orbit coupling (SOC) or low-lying excited states, hence posing challenges to perform spin readout at scale and with high fidelity in such systems. Here, we present a method, based on the dependence of the two-spin system polarizability on energy detuning, to perform spin state readout even when SB lifting mechanisms are dominant. It leverages SB lifting as a resource to detect selectively different spin measurement outcomes. We demonstrate the method using a hybrid system formed by a quantum dot (QD) and a Boron acceptor in a silicon p-type transistor and show spin-selective readout of different spin states under SB lifting conditions due to (i) SOC and (ii) low-lying orbital states in the QD. We further use the method to determine the detuning-dependent spin relaxation time of 0.1 - 8 $\mu$s. Our method should help perform projective spin measurements with high spin-to-charge conversion fidelity in systems subject to strong SOC, will facilitate state leakage detection and enable complete readout of two-spin states.

cond-mat.mes-hall↗

arXiv2019

Electric-field control and noise protection of the flopping-mode spin qubit

We propose and analyze a novel "flopping-mode" mechanism for electric dipole spin resonance based on the delocalization of a single electron across a double quantum dot confinement potential. Delocalization of the charge maximizes the electronic dipole moment compared to the conventional single dot spin resonance configuration. We present a theoretical investigation of the flopping-mode spin qubit properties through the crossover from the double to the single dot configuration by calculating effective spin Rabi frequencies and single-qubit gate fidelities. The flopping-mode regime optimizes the artificial spin-orbit effect generated by an external micromagnet and draws on the existence of an externally controllable sweet spot, where the coupling of the qubit to charge noise is highly suppressed. We further analyze the sweet spot behavior in the presence of a longitudinal magnetic field gradient, which gives rise to a second order sweet spot with reduced sensitivity to charge fluctuations.

cond-mat.mes-hall↗