arXiv subjects

Hsiang-Yu Lo

Publications and source records attributed to Hsiang-Yu Lo.

6 recordsLinked to original sources

arXiv2025

Reducing Ion Heating in Quantum Computing: A Novel 3D-Printed Micro Ion Trap with Skeleton Structure

Electric-field-induced ion heating is a major obstacle in scalable trapped-ion quantum computing. We present a theoretical study of a novel 3D-printed ion trap with a skeleton electrode structure, designed to reduce heating by minimizing surface area near the ion. Compared to a conventional blade trap with identical confinement parameters, the skeleton trap achieves over 50% reduction in total heating rate. Patch-by-patch analysis reveals that heating is dominated by surfaces within 500 μm of the ion. For axial motion, the peak heating occurs approximately 110 μm away due to electric field directionality. We demonstrate that minor geometric optimization, in which the electrode gaps are realigned with these hotspots, can further suppress heating despite the associated increase in surface area. A linear relationship between ion-to-electrode distance and peak heating location is also established. These results highlight the potential of 3D-printed electrode designs for achieving both strong confinement and reduced noise in future quantum systems.

quant-ph↗

arXiv2018

Repeated multi-qubit readout and feedback with a mixed-species trapped-ion register

Quantum error correction will be essential for realizing the full potential of large-scale quantum information processing devices. Fundamental to its experimental realization is the repetitive detection of errors via projective measurements of quantum correlations among qubits, and correction using conditional feedback. Performing these tasks repeatedly requires a system in which measurement and feedback decision times are short compared to qubit coherence times, where the measurement reproduces faithfully the desired projection, and for which the measurement process has no detrimental effect on the ability to perform further operations. Here we demonstrate up to 50 sequential measurements of correlations between two beryllium-ion qubits using a calcium ion ancilla, and implement feedback which allows us to stabilize two-qubit subspaces as well as Bell states. Multi-qubit mixed-species gates are used to transfer information from qubits to the ancilla, enabling quantum state detection with negligible crosstalk to the stored qubits. Heating of the ion motion during detection is mitigated using sympathetic recooling. A key element of the experimental system is a powerful classical control system, which features flexible in-sequence processing to implement feedback control. The methods employed here provide a number of essential ingredients for scaling trapped-ion quantum computing, and provide new opportunities for quantum state control and entanglement-enhanced quantum metrology.

quant-ph↗

arXiv2016

Large Cross-Phase Modulations at the Few-Photon Level

We demonstrate an efficient cross-phase modulation (XPM) based on a closed-loop double-Λ system. The property of the double-Λ medium can be controlled by changing the phases of the applied optical fields. This phase-dependent XPM scheme can achieve large phase modulations at low-light intensities without requiring cavities or tightly focusing of laser beams. With this scheme, we observe a π-level phase shift with two pulses both consisting of 8 photons in cold rubidium atoms. Such novel scheme provides a simple route to generate strong interactions between photons and may have potential applications in all-optical quantum signal processing.

quant-ph↗

arXiv2016

Parallel transport quantum logic gates with trapped ions

We demonstrate single-qubit operations by transporting a beryllium ion with a controlled velocity through a stationary laser beam. We use these to perform coherent sequences of quantum operations, and to perform parallel quantum logic gates on two ions in different processing zones of a multiplexed ion trap chip using a single recycled laser beam. For the latter, we demonstrate individually addressed single-qubit gates by local control of the speed of each ion. The fidelities we observe are consistent with operations performed using standard methods involving static ions and pulsed laser fields. This work therefore provides a path to scalable ion trap quantum computing with reduced requirements on the optical control complexity.

quant-ph↗

arXiv2015

Spin-motion entanglement and state diagnosis with squeezed oscillator wavepackets

Mesoscopic superpositions of distinguishable coherent states provide an analog to the Schrödinger's cat thought experiment. For mechanical oscillators these have primarily been realised using coherent wavepackets, for which the distinguishability arises due to the spatial separation of the superposed states. Here, we demonstrate superpositions composed of squeezed wavepackets, which we generate by applying an internal-state dependent force to a single trapped ion initialized in a squeezed vacuum state with 9 dB reduction in the quadrature variance. This allows us to characterise the initial squeezed wavepacket by monitoring the onset of spin-motion entanglement, and to verify the evolution of the number states of the oscillator as a function of the duration of the force. In both cases, we observe clear differences between displacements aligned with the squeezed and anti-squeezed axes. We observe coherent revivals when inverting the state-dependent force after separating the wavepackets by more than 19 times the ground-state root mean squared extent, which corresponds to 56 times the root mean squared extent of the squeezed wavepacket along the displacement direction. Aside from their fundamental nature, these states may be useful for quantum metrology or quantum information processing with continuous variables.

quant-ph↗

arXiv2013

Few-Photon All-Optical π Phase modulation Based on a Double-Λ System

We propose an efficient all-optical phase modulation based on a double-Λ system and demonstrate a π phase shift of a few-photon pulse induced by another few-photon pulse in cold rubidium atoms with this scheme. By changing the phases of the applied laser fields, one can control the property of the double-Λ medium. This phase-dependent mechanism makes the double-Λ system different form the conventional cross-Kerr-based system which only depends on the applied laser intensities. The proposed scheme provides a new route to generate strong nonlinear interactions between photons, and may have potential for applications in quantum information technologies.

physics.optics↗