arXiv subjects

Jorge Monroy-Ruz

Publications and source records attributed to Jorge Monroy-Ruz.

6 recordsLinked to original sources

arXiv2024

Piezoelectric microresonators for sensitive spin detection

Piezoelectric microresonators are indispensable in wireless communications, and underpin radio frequency filtering in mobile phones. These devices are usually analyzed in the quasi-(electro)static regime with the magnetic field effectively ignored. On the other hand, at GHz frequencies and especially in piezoelectric devices exploiting strong dimensional confinement of acoustic fields, the surface magnetic fields ($B_{1}$) can be significant. This $B_1$ field, which oscillates at GHz frequencies, but is confined to ${\mu}$m-scale wavelengths provides a natural route to efficiently interface with nanoscale spin systems. We show through scaling arguments that $B_1{\propto}f^2$ for tightly focused acoustic fields at a given operation frequency $f$. We demonstrate the existence of these surface magnetic fields in a proof-of-principle experiment by showing excess power absorption at the focus of a surface acoustic wave (SAW), when a polished Yttrium-Iron-Garnet (YIG) sphere is positioned in the evanescent field, and the magnon resonance is tuned across the SAW transmission. Finally, we outline the prospects for sensitive spin detection using small mode volume piezoelectric microresonators, including the feasibility of electrical detection of single spins at cryogenic temperatures.

physics.app-ph↗

arXiv2023

Heterogeneous integration of solid state quantum systems with a foundry photonics platform

Diamond colour centres are promising optically-addressable solid state spins that can be matter-qubits, mediate deterministic interaction between photons and act as single photon emitters. Useful quantum computers will comprise millions of logical qubits. To become useful in constructing quantum computers, spin-photon interfaces must therefore become scalable and be compatible with mass-manufacturable photonics and electronics. Here we demonstrate heterogeneous integration of NV centres in nanodiamond with low-fluorescence silicon nitride photonics from a standard 180 nm CMOS foundry process. Nanodiamonds are positioned over pre-defined sites in a regular array on a waveguide, in a single post-processing step. Using an array of optical fibres, we excite NV centres selectively from an array of six integrated nanodiamond sites, and collect the photoluminescence (PL) in each case into waveguide circuitry on-chip. We verify single photon emission by an on-chip Hanbury Brown and Twiss cross-correlation measurement, which is a key characterisation experiment otherwise typically performed routinely with discrete optics. Our work opens up a simple and effective route to simultaneously address large arrays of individual optically-active spins at scale, without requiring discrete bulk optical setups. This is enabled by the heterogeneous integration of NV centre nanodiamonds with CMOS photonics.

quant-ph↗

arXiv2022

Sub-{\mu}m axial precision depth imaging with entangled two-colour Hong-Ou-Mandel microscopy

The quantum interference of two wavelength-entangled photons overlapping at a beamsplitter results in an oscillating interference pattern. The frequency of the beat note is dependent on the wavelength separation of the entangled photons but is robust to wavelength scale perturbations that can limit the practicality of standard interferometry. Here we use two-colour entanglement interferometry to evaluate the variation in thickness of a semi-transparent sample in combination with two-dimensional raster scanning. The axial precision and the dynamic range of the microscope are actively controlled by adjusting the wavelength separation of the entangled photon pairs. Sub-$\mu m$ precision is reported using up to $12.3~nm$ of detuning and $\sim10^4$ detected photon pairs.

quant-ph↗

arXiv2021

Towards compact high-efficiency grating couplers for visible wavelength photonics

While grating couplers have become the de-facto standard for optical access to integrated silicon photonics platforms, their performance at visible wavelengths, in moderate index contrast platforms like silicon nitride, leaves significant room for improvement. In particular, the index contrast governs the diffraction efficiency per grating tooth and the resulting overall coupler length. In this work, we develop two approaches to address this problem: a dielectric grating that sums multiple optical modes to increase the overall output intensity, and an embedded metal grating that enhances the attainable refractive index contrast, and therefore reduces the on-chip footprint. We present experimental results that can be developed to realise compact efficient visible wavelength photonic interconnects, with a view towards cryogenic deployment for quantum photonics, where space is constrained and efficiency is critical.

physics.optics↗

arXiv2019

Single photon emission and single spin coherence of a nitrogen vacancy centre encapsulated in silicon nitride

Finding the right material platform for engineering efficient photonic interfaces to solid state emitters has been a long-standing bottleneck for scaling up solid state quantum systems. In this work, we demonstrate that nitrogen-rich silicon nitride, with its low background auto-fluorescence at visible wavelengths, is a viable quantum photonics platform by showing that nitrogen vacancy centres embedded in nanodiamonds preserve both their quantum optical and spin properties post-encapsulation. Given the variety of high-performance photonic components already demonstrated in silicon nitride, our work opens up a new avenue for building integrated photonic circuits using solid state emitters.

physics.app-ph↗

arXiv2016

Counter-propagating spontaneous four wave mixing: photon-pair factorability and ultra-narrowband single photon

We introduce a new kind of spontaneous four wave mixing process for the generation of photon pairs, in which the four waves involved counter-propagate in a guided-wave \chi^{(3)} medium; we refer to this process as counter-propagating spontaneous four wave mixing (CP-SFWM). We show that for the simplest CP-SFWM source, in which all waves propagate in the same polarization and transverse mode and in which self- and cross-phase modulation effects are negligible, phasematching is attained automatically regardless of dispersion in the fiber or waveguide. Furthermore, we show that in two distinct versions of this source (both pumps pulsed, or one pump pulsed and the remaining one monochromatic), the two-photon state is automatically factorable provided that the length of the nonlinear medium exceeds a certain threshold, easily achievable in practice since this threshold length tends to be in the range of mm to cm. We also show that if one of the pumps approaches the monochromatic limit, and for a sufficient nonlinear medium length, the bandwidth of one of the two photons in a given pair may be reduced to the level of MHz, compatible with electronic transitions for the implementation of atom-photon interfaces, without the use of optical cavities.

quant-ph↗