arXiv subjects

J. Tu

Publications and source records attributed to J. Tu.

4 recordsLinked to original sources

arXiv2026

Dual-species alkali and alkaline-earth-like optical tweezer arrays via interferometrically aligned high-NA objectives

We have developed a dual-species optical tweezer array apparatus combining $^{87}\text{Rb}$ and $^{174}\text{Yb}$ atoms with a permanent hybrid Twyman-Green--Fizeau interferometer, which provides precision co-alignment of two opposing 0.6-numerical aperture (NA) objectives and the high NA beams that pass through the system. This technique is extensible to other tweezer platforms operating at high numerical aperture across widely-separated wavelengths. Here we present simultaneous trapping and single-site resolved imaging of both species in co-aligned tweezer arrays with $^{87}\text{Rb}$ confined at $840\ \rm{nm}$ and $^{174}\text{Yb}$ at $532\ \rm{nm}$. The platform provides a foundation for hybrid quantum register operation, including mid-circuit measurements and asymmetric intra- and inter-species interactions, greatly expanding the capabilities of neutral atom arrays.

physics.atom-ph↗

arXiv2024

Quadrature amplitude modulation for electronic sideband Pound-Drever-Hall laser frequency locking

The Pound--Drever--Hall (PDH) technique is routinely used to stabilize the frequency of a laser to a reference cavity. Electronic sideband (ESB) locking, a PDH variant, bridges the frequency gap between the discrete cavity resonances and a desired laser frequency. Here we use quadrature amplitude modulation (QAM), a standard technique in digital communications, to generate the high-quality phase-modulated radio-frequency (rf) drive required for ESB locking. We develop a theoretical framework to analyze how in-phase/quadrature-phase (I/Q) impairments distort the ESB error signal and induce frequency offsets relevant to ultranarrow-linewidth lasers. We then design and implement a direct software-defined radio (SDR) on an UltraScale+ RFSoC platform, frequently adopted across modern quantum-computing systems, to digitally compensate QAM I/Q impairments. Using this device, we generate phase-modulated rf signals with a large phase-modulation index of $1.01$ rad and root-mean-square I/Q errors below $0.3\ \%$ over a carrier-frequency range of $350~\mathrm{MHz}$ to $1.75~\mathrm{GHz}$. Finally, we lock a laser to an ultralow expansion (ULE) reference cavity and demonstrate continuous laser-frequency tuning by ramping the carrier frequency while maintaining lock, validating the continuous tunability of our ESB locking instrument.

physics.optics↗

arXiv2020

Discriminative Feature Representation with Spatio-temporal Cues for Vehicle Re-identification

Vehicle re-identification (re-ID) aims to discover and match the target vehicles from a gallery image set taken by different cameras on a wide range of road networks. It is crucial for lots of applications such as security surveillance and traffic management. The remarkably similar appearances of distinct vehicles and the significant changes of viewpoints and illumination conditions take grand challenges to vehicle re-ID. Conventional solutions focus on designing global visual appearances without sufficient consideration of vehicles' spatiotamporal relationships in different images. In this paper, we propose a novel discriminative feature representation with spatiotemporal clues (DFR-ST) for vehicle re-ID. It is capable of building robust features in the embedding space by involving appearance and spatio-temporal information. Based on this multi-modal information, the proposed DFR-ST constructs an appearance model for a multi-grained visual representation by a two-stream architecture and a spatio-temporal metric to provide complementary information. Experimental results on two public datasets demonstrate DFR-ST outperforms the state-of-the-art methods, which validate the effectiveness of the proposed method.

cs.CV↗

arXiv2011

Harry Potter's Cloak

The magic "Harry Potter's cloak" has been the dream of human beings for really long time. Recently, transformation optics inspired from the advent of metamaterials offers great versatility for manipulating wave propagation at will to create amazing illusion effects. In the present work, we proposed a novel transformation recipe, in which the cloaking shell somehow behaves like a "cloaking lens", to provide almost all desired features one can expect for a real magic cloak. The most exciting feature of the current recipe is that an object with arbitrary characteristics (e.g., size, shape or material properties) can be invisibilized perfectly with positive-index materials, which significantly benefits the practical realization of a broad-band cloaking device fabricated with existing materials. Moreover, the one concealed in the hidden region is able to undistortedly communicate with the surrounding world, while the lens-like cloaking shell will protect the cloaked source/sensor from being traced back by outside detectors by creating a virtual image.

physics.class-ph↗