arXiv subjects

Aaron M. Day

Publications and source records attributed to Aaron M. Day.

11 recordsLinked to original sources

arXiv2026

Resolving and resetting the charge environment of single T-centers in silicon p-i-n waveguides

The silicon T-center is a telecom-band spin-photon interface in a manufacturable photonics platform. In nanophotonic devices, however, its optical linewidth is broadened by a fluctuating charge environment, limiting photon indistinguishability for quantum networking. Here, we address this challenge through characterization and suppression of the local charge-noise of single T-centers in lateral p-i-n waveguides, demonstrating an unheralded method of T-center optical linewidth narrowing. Above-band illumination resets the charge environment, neutralizing the local field and suppressing spectral diffusion. Across 46 emitters this reset narrows the median linewidth 3.5-fold to 0.57(11) GHz, and an optimized emitter reaches 128(22) MHz, the narrowest unheralded linewidth reported for an integrated T-center. The narrowed transition supports coherent optical Rabi oscillations with a coherence time of 20(2) ns. Finally, we perform Stark-shift tuning using the p-i-n junction, and read out the local electric field and the charge-noise width at 15 mK. An analytical model of proximal surfaces, bulk, and junction field effects provides good agreement with our findings. Our multi-pronged characterization of the nanophotonic-integrated T-center charge environment enables future device optimization toward scalable quantum interconnects.

quant-ph↗

arXiv2026

The Evolution of Magnetism in a Thin Film Pyrochlore Ferromagnetic Insulator

The pyrochlore vanadates are compelling candidates for next-generation dissipationless devices. Lu2V2O7 and Y2V2O7 are ferromagnetic insulators (Tc ~ 70 K) that are believed to exhibit the magnon Hall effect and are expected to host topological magnons. Their completely dissipationless magnon edge states could be harnessed to realize low-power information transport in spintronic or magnonic devices. As a crucial step in the realization of devices, we synthesize the first thin films of pyrochlore Y2V2O7 on isostructural Y2Ti2O7 substrates and explore the evolution of their magnetic properties down to the ultrathin limit. All films are insulating ferromagnets with transition temperatures of up to the bulk value (Tc ~ 68 K) that decrease with thickness according to finite-size effects. Our films also exhibit a change in anisotropy from in-plane to out-of-plane easy axis coincident with the development of partial strain relaxation and nonzero magnetic hysteresis in an applied field. This evolution demonstrates the impact of strain on magnetic anisotropy and paves the way to tunable magnon topology.

cond-mat.mtrl-sci↗

arXiv2026

Ultracoherent self-assembled diamond nanomechanics reveals superfluid dynamics

From gravitational-wave detection, protein force microscopy, to exploration of quantum-classical boundaries, many anticipated discoveries in fundamental science require improving measurement sensitivity limits. Through the fluctuation-dissipation theorem, mechanical dissipation sets the acoustic noise for this limit. Yet, even in high-purity crystals, the microscopic mechanisms responsible for the acoustic loss remain poorly understood. Tension-induced dissipation dilution offers a route to ultralow acoustic loss, but is challenging to implement in crystalline materials including single-crystal diamond. Here we realize a strain-engineered diamond nanomechanical platform using a liquid-assisted van der Waals self-assembly process that harnesses intrinsic surface forces to apply tensile stress exceeding 1 GPa. At cryogenic temperatures these resonators achieve quality factors beyond 10 billion (intrinsic material quality factors beyond 100 million). This exceptional coherence turns them into a sensitive probe for residual dissipation, elucidating three distinct two-level-system channels and one topological dissipation channel from a surface superfluid helium film. Our work shows how advancing mechanical coherence opens access to new regimes of physics in hybrid quantum systems, precision metrology, and condensed-matter physics.

cond-mat.mes-hall↗

arXiv2026

Heterogeneous Transfer of Thin Film BaTiO$_3$ onto Silicon for Device Fabrication

Thin film BaTiO$_3$ has one of the highest known Pockels coefficients (>1200 pm/V), making it an attractive material for use in electro-optic devices. It is advantageous to integrate BaTiO$_3$ on silicon to enable complementary metal-oxide-semiconductor (CMOS) compatible processing. However, synthesis of high-quality BaTiO$_3$ directly on silicon remains a challenge. Here, we synthesize BaTiO$_3$ using hybrid metal-organic molecular beam epitaxy (hMBE) and demonstrate its transfer onto silicon using thermocompression bonding and chemical lift-off. Hybrid metal-organic MBE enables self-regulated synthesis of highly stoichiometric thin films at high growth rates (>100nm/hr). Our transfer method results in millimeter-scale areas of atomically flat, crack-free BaTiO$_3$ making it a potentially scalable method. Finally, we demonstrate the applicability of our process to device fabrication through characterization of lithographically-patterned and etch-transferred sub-micron features.

cond-mat.mtrl-sci↗

arXiv2026

Probing negative differential resistance in silicon with a P-I-N diode-integrated T center ensemble

Solid-state defect quantum systems are exquisite probes of their local charge environment. Nonlinear dynamical electric fields in solids are challenging to characterize directly, conventionally limited to coarse macroscopic methods which fail to capture subtle effects in the material. Here, through transient optical spectroscopy on an embedded T center ensemble, we realize the in-situ observation of a silicon PIN-diode phase transition to a regime of self-sustained carrier oscillatory dynamics characteristic of negative differential resistance. Manifest in both the ensemble electroluminescence and photoluminescence, we find a temperature and field-dependent phase space for persistent undamped amplitude oscillations indicative of a collective ensemble response to the field dynamics. These findings shed new light on the cryogenic behavior of silicon, provide fundamental insight into the physics of the T center for improved quantum device performance, and open a promising new direction for defect-based local quantum sensing in semiconductor devices.

quant-ph↗

arXiv2025

A Suspended 4H-Silicon Carbide Membrane Platform for Defect Integration into Quantum Devices

4H-silicon carbide is a promising platform for solid-state quantum technology due to its commercial availability as a wide bandgap semiconductor and ability to host numerous spin-active color centers. Integrating color centers into suspended nanodevices enhances defect control and readout--key advances needed to fully harness their potential. However, challenges in developing robust fabrication processes for 4H-SiC thin films--due to the material's chemical and mechanical stability--limit their implementation in quantum applications. Here, we report on a new fabrication approach that first synthesizes suspended thin films from a monolithic platform, then patterns devices. With this technique, we fabricate and characterize structures tailored for defect integration, demonstrating 1D photonic crystal cavities, with and without waveguide interfaces, and lithium niobate on 4H-SiC acoustic cavities. This approach allows for greater fabrication flexibility--supporting high temperature annealing and heterogeneous material platform compatibility--providing a versatile platform for scalable fabrication of 4H-SiC devices for quantum technologies.

physics.app-ph↗

arXiv2024

Selective Undercut of Undoped Optical Membranes for Spin-Active Color Centers in 4H-SiC

Silicon carbide (SiC) is a semiconductor used in quantum information processing, microelectromechanical systems, photonics, power electronics, and harsh environment sensors. However, its high temperature stability, high breakdown voltage, wide bandgap, and high mechanical strength are accompanied by a chemical inertness which makes complex micromachining difficult. Photoelectrochemical etching is a simple, rapid means of wet processing SiC, including the use of dopant selective etch stops that take advantage of mature SiC homoepitaxy. However, dopant selective photoelectrochemical etching typically relies on highly doped material, which poses challenges for device applications such as quantum defects and photonics that benefit from low doping to produce robust emitter properties and high optical transparency. In this work, we develop a new, selective photoelectrochemical etching process that relies not on high doping but on the electrical depletion of a fabricated diode structure, allowing the selective etching of an n-doped substrate wafer versus an undoped epitaxial ($N_a=1(10)^{14}cm^{-3}$) device layer. We characterize the photo-response and photoelectrochemical etching behavior of the diode under bias and use those insights to suspend large ($>100μm^2$) undoped membranes of SiC. We further characterize the compatibility of membranes with quantum emitters, performing comparative spin spectroscopy between undoped and highly doped membrane structures, finding the use of undoped material improves ensemble spin lifetime by $>3x$. This work enables the fabrication of high-purity suspended thin films suitable for scalable photonics, mechanics, and quantum technologies in SiC.

physics.app-ph↗

arXiv2023

Electrical Manipulation of Telecom Color Centers in Silicon

Silicon color centers have recently emerged as promising candidates for commercial quantum technology, yet their interaction with electric fields has yet to be investigated. In this paper, we demonstrate electrical manipulation of telecom silicon color centers by fabricating lateral electrical diodes with an integrated G center ensemble in a commercial silicon on insulator wafer. The ensemble optical response is characterized under application of a reverse-biased DC electric field, observing both 100% modulation of fluorescence signal, and wavelength redshift of approximately 1.4 GHz/V above a threshold voltage. Finally, we use G center fluorescence to directly image the electric field distribution within the devices, obtaining insight into the spatial and voltage-dependent variation of the junction depletion region and the associated mediating effects on the ensemble. Strong correlation between emitter-field coupling and generated photocurrent is observed. Our demonstration enables electrical control and stabilization of semiconductor quantum emitters.

quant-ph↗

arXiv2023

Deterministic Creation of Strained Color Centers in Nanostructures via High-Stress Thin Films

Color centers have emerged as a leading qubit candidate for realizing hybrid spin-photon quantum information technology. One major limitation of the platform, however, is that the characteristics of individual color-centers are often strain dependent. As an illustrative case, the silicon-vacancy center in diamond typically requires millikelvin temperatures in order to achieve long coherence properties, but strained silicon vacancy centers have been shown to operate at temperatures beyond 1K without phonon-mediated decoherence. In this work we combine high-stress silicon nitride thin films with diamond nanostructures in order to reproducibly create statically strained silicon-vacancy color centers (mean ground state splitting of 608 GHz) with strain magnitudes of $\sim 4 \times 10^{-4}$. Based on modeling, this strain should be sufficient to allow for operation of a majority silicon-vacancy centers within the measured sample at elevated temperatures (1.5K) without any degradation of their spin properties. This method offers a scalable approach to fabricate high-temperature operation quantum memories. Beyond silicon-vacancy centers, this method is sufficiently general that it can be easily extended to other platforms as well.

quant-ph↗

arXiv2022

Deterministic Laser Writing of Spin Defects in Nanophotonic Cavities

High-yield engineering and characterization of cavity-emitter coupling is an outstanding challenge in developing scalable quantum network nodes. Ex-situ defect formation processes prevent real-time defect-cavity characterization, and previous in-situ methods require further processing to improve emitter properties or are limited to bulk substrates. We demonstrate direct laser-writing of cavity-integrated spin defects using a nanosecond-pulsed above-bandgap laser. Photonic crystal cavities in 4H-silicon carbide serve as a nanoscope monitoring silicon monovacancy (V$_{Si}^-$) defect formation within the $100~\text{nm}^3$ cavity mode volume. We observe defect spin resonance, cavity-integrated photoluminescence and excited-state lifetimes consistent with conventional defect formation methods, without need for post-irradiation thermal annealing. We further find an exponential reduction in excited-state lifetime at fluences approaching the cavity amorphization threshold, and show single-shot local annealing of the intrinsic background defects at the V$_{Si}^-$ formation sites. This real-time in-situ method of localized defect formation, paired with demonstration of cavity-integrated defect spins, marks an important step in engineering cavity-emitter coupling for quantum networking.

physics.app-ph↗

arXiv2022

Spin-Acoustic Control of Silicon Vacancies in 4H Silicon Carbide

We demonstrate direct, acoustically mediated spin control of naturally occurring negatively charged silicon monovacancies (V$_{Si}^-$) in a high quality factor Lateral Overtone Bulk Acoustic Resonator fabricated out of high purity semi-insulating 4H-Silicon Carbide. We compare the frequency response of silicon monovacancies to a radio-frequency magnetic drive via optically-detected magnetic resonance and the resonator's own radio-frequency acoustic drive via optically-detected spin acoustic resonance and observe a narrowing of the spin transition to nearly the linewidth of the driving acoustic resonance. We show that acoustic driving can be used at room temperature to induce coherent population oscillations. Spin acoustic resonance is then leveraged to perform stress metrology of the lateral overtone bulk acoustic resonator, showing for the first time the stress distribution inside a bulk acoustic wave resonator. Our work can be applied to the characterization of high quality-factor micro-electro-mechanical systems and has the potential to be extended to a mechanically addressable quantum memory.

physics.app-ph↗