arXiv subjects

Fernando Torres-Leal

Publications and source records attributed to Fernando Torres-Leal.

3 recordsLinked to original sources

arXiv2026

Towards polarization steganography

We propose and experimentally demonstrate a polarization--based steganographic scheme using partially polarized vector beams. In our approach, the spatially dependent polarization structure of the optical field serves as the carrier through which the hidden information can be retrieved. By engineering a vector beam whose polarization states populate a prescribed region of the Poincar\'e sphere, specifically, the equatorial disk, we establish a nontrivial mapping between transverse spatial coordinates and polarization states. Information retrieval is achieved by applying a spatial mask derived from a parametric curve defined within this region of the Poincar\'e sphere, followed by spatially resolved polarization analysis. We demonstrate the selective reconstruction of various parametric shapes, including polygonal and smooth curves, confirming that the hidden patterns are retrieved through the combined use of spatial filtering and polarization--domain mapping. Our results establish partially polarized vector beams as a flexible and experimentally accessible platform for polarization--based information hiding.

physics.optics↗

arXiv2026

Measuring and correcting nanosecond pulse distortions in quantum-dot spin qubits

Gate-defined semiconductor quantum dots utilize fast electrical control to manipulate spin and charge states of individual electrons. Electrical pulse distortions can limit control fidelities but are difficult to measure at the device level. Here, we use detuning-axis pulsed spectroscopy to characterize baseband pulse distortions in a silicon double quantum-dot. We extract the gate-voltage impulse response and apply a digital pre-distortion filter to eliminate pulse distortions on timescales longer than 1~ns. With the pre-distortion, we reduce the frequency chirp of coherent exchange oscillations in a singlet-triplet qubit. Our results suggest a scalable and tuning-efficient method for characterizing pulse distortions in quantum-dot spin qubits.

quant-ph↗

arXiv2025

Mitigating Residual Exchange Coupling in Resonant Singlet-Triplet Qubits

We propose methods to mitigate single- and two-qubit control errors due to residual exchange coupling in systems of exchange-coupled resonant singlet-triplet qubits. Commensurate driving, where the pulse length is an integer multiple of the drive period, can mitigate errors from residual intra-qubit exchange, including effects from counter rotating terms and off-axis rotations, as well as leakage errors during two-qubit operations. Residual inter-qubit exchange creates crosstalk errors that reduce single-qubit control fidelities. We show that using a single-spin coupler between two resonant singlet-triplet qubits can reduce this crosstalk error by an order of magnitude. Assuming perfect coupler state preparation and realistic charge and hyperfine noise, we predict that coupler-assisted two-qubit gate errors can be below $3\times10^{-3}$ for gate times as short as $66~\text{ns}$, even in the presence of residual exchange levels exceeding several hundred kHz. Our results suggest the potential of utilizing coupler-based architectures for large scale fault-tolerant spin qubit processors based on resonant singlet-triplet qubits.

quant-ph↗