arXiv subjects

M. Trupke

Publications and source records attributed to M. Trupke.

At least 19 recordsLinked to original sources

arXiv2026

Demonstration Of A Quantum Magnetometer Chip Based On Proprietary And Scalable 4H-Silicon Carbide Technology

This work presents an industrially scalable, power-efficient and high-performance quantum magnetometer chip based on proprietary 4H-silicon carbide (SiC) technology, leveraging wafer-scale fabrication techniques to optimize V2 silicon vacancy color centers for highly reproducible, industry-grade fabrication with precise control of depth and density. The integration of these color center ensembles into a planar silicon carbide waveguide enables efficient excitation of a large ensemble and simplifies fluorescence extraction compared to standard confocal methods. We report continuous-wave (CW) optically detected magnetic resonance measurements, complemented by Rabi, Ramsey, and Hahn-echo sequences, which demonstrate coherent capabilities of the large embedded ensemble of V2 centers. Based on the data, our device exhibits sensor shot-noise limited sensitivities 2-3 orders of magnitude lower compared to more complex confocal techniques. Collectively, these advancements simplify the quantum sensor architecture, enhance sensitivity, and streamline optical excitation and collection, thereby paving the way for the development of next-generation SiC-quantum sensing technologies.

quant-ph↗

arXiv2025

Optical Interferometric Readout of a Magnetically Levitated Superconducting Microsphere

We probe the motion of a 6 $\mu g$ magnetically levitated superconducting microsphere using optical interferometry at 3 K, achieving a resolution better than 1 $nm/ \sqrt{Hz}$, and use the measured signal to feedback-cool its motion. The resolution exceeds the shot-noise limit of 11 $pm/ \sqrt{Hz}$ primarily due to technical noise arising from the roughness of the particle. Combined with established techniques of cavity optomechanics, the high degree of isolation from environmental noise afforded by this platform provides a path to quantum physics experiments with cryogenic isolated masses at the microgram scale.

quant-ph↗

arXiv2022

Vanadium in Silicon Carbide: Telecom-ready spin centres with long relaxation lifetimes and hyperfine-resolved optical transitions

Vanadium in silicon carbide (SiC) is emerging as an important candidate system for quantum technology due to its optical transitions in the telecom wavelength range. However, several key characteristics of this defect family including their spin relaxation lifetime (T1), charge state dynamics, and level structure are not fully understood. In this work, we determine the T1 of an ensemble of vanadium defects, demonstrating that it can be greatly enhanced at low temperature. We observe a large spin contrast exceeding 90% and long spin-relaxation times of up to 25s at 100mK, and of order 1s at 1.3K. These measurements are complemented by a characterization of the ensemble charge state dynamics. The stable electron spin furthermore enables high-resolution characterization of the systems' hyperfine level structure via two-photon magneto-spectroscopy. The acquired insights point towards high-performance spin-photon interfaces based on vanadium in SiC.

quant-ph↗

arXiv2019

Influence of irradiation on defect spin coherence in silicon carbide

Irradiation-induced lattice defects in silicon carbide (SiC) have already exceeded their previous reputation as purely performance-inhibiting. With their remarkable quantum properties, such as long room-temperature spin coherence and the possibility of downscaling to single-photon source level, they have proven to be promising candidates for a multitude of quantum information applications. One of the most crucial parameters of any quantum system is how long its quantum coherence can be preserved. By using the pulsed optically detected magnetic resonance (ODMR) technique, we investigate the spin-lattice relaxation time ($T_1$) and spin coherence time ($T_2$) of silicon vacancies in 4H-SiC created by neutron, electron and proton irradiation in a broad range of fluences. We also examine the effect of irradiation energy and sample annealing. We establish a robustness of the $T_1$ time against all types of irradiation and reveal a universal scaling of the $T_2$ time with the emitter density. Our results can be used to optimize the coherence properties of silicon vacancy qubits in SiC for specific tasks.

cond-mat.mtrl-sci↗

arXiv2019

Optical Properties of Vanadium in 4H Silicon Carbide for Quantum Technology

We study the optical properties of tetravalent vanadium impurities in 4H silicon carbide (4H SiC). Emission from two crystalline sites is observed at wavelengths of 1.28 \mum and 1.33 \mum, with optical lifetimes of 163 ns and 43 ns. Group theory and ab initio density functional supercell calculations enable unequivocal site assignment and shed light on the spectral features of the defects. We conclude with a brief outlook on applications in quantum photonics.

quant-ph↗

arXiv2019

Silicon microcavity arrays with open access and a finesse of half a million

Optical resonators are increasingly important tools in science and technology. Their applications range from laser physics, atomic clocks, molecular spectroscopy, and single-photon generation to the detection, trapping and cooling of atoms or nano-scale objects. Many of these applications benefit from strong mode confinement and high optical quality factors, making small mirrors of high surface-quality desirable. Building such devices in silicon yields ultra-low absorption at telecom wavelengths and enables integration of micro-structures with mechanical, electrical and other functionalities. Here, we push optical resonator technology to new limits by fabricating lithographically aligned silicon mirrors with ultra-smooth surfaces, small and wellcontrolled radii of curvature, ultra-low loss and high reflectivity. We build large arrays of microcavities with finesse greater than F = 500,000 and a mode volume of 330 femtoliters at wavelengths near 1550 nm. Such high-quality micro-mirrors open up a new regime of optics and enable unprecedented explorations of strong coupling between light and matter.

physics.app-ph↗

arXiv2016

Enhanced dual-beam excitation photoelectric detection of NV magnetic resonances in diamond

The core issue for the implementation of the diamond NV centre qubits technology is the sensitive readout of NV spin state. We have recently demonstrated the photoelectric detection of NV magnetic resonances (PDMR), anticipated to be faster and more sensitive than optical detection (ODMR). Here we report on a PDMR contrast of 9 % - three times enhanced compared to previous work - on shallow N-implanted diamond. Based on ab-initio modelling, we demonstrate a novel one-photon ionization dual-beam PDMR protocol. We predict that this scheme is significantly less vulnerable to the influence of defects such as substitutional nitrogen.

cond-mat.mes-hall↗

arXiv2016

All-optical dc nanotesla magnetometry using silicon vacancy fine structure in isotopically purified silicon carbide

We uncover the fine structure of a silicon vacancy in isotopically purified silicon carbide (4H-$^{28}$SiC) and find extra terms in the spin Hamiltonian, originated from the trigonal pyramidal symmetry of this spin-3/2 color center. These terms give rise to additional spin transitions, which are otherwise forbidden, and lead to a level anticrossing in an external magnetic field. We observe a sharp variation of the photoluminescence intensity in the vicinity of this level anticrossing, which can be used for a purely all-optical sensing of the magnetic field. We achieve dc magnetic field sensitivity of 87 nT Hz$^{-1/2}$ within a volume of $3 \times 10^{-7}$ mm$^{3}$ at room temperature and demonstrate that this contactless method is robust at high temperatures up to at least 500 K. As our approach does not require application of radiofrequency fields, it is scalable to much larger volumes. For an optimized light-trapping waveguide of 3 mm$^{3}$ the projection noise limit is below 100 fT Hz$^{-1/2}$.

cond-mat.mtrl-sci↗

arXiv2015

Subnanotesla quantum-interference magnetometry with a single spin in diamond

We demonstrate a magnetometry technique using nitrogen-vacancy centres in diamond which makes use of coherent two-photon transitions. We find that the sensitivity to magnetic fields can be significantly improved in isotopically purified diamond. Furthermore, the long-term stability of magnetic field measurements is significantly enhanced, thereby reducing the minimum detectable long-term field variations for both quasi-static and periodic fields. The method is useful both for sensing applications and as a spin qubit manipulation technique.

quant-ph↗

arXiv2014

Photonic Quantum Networks formed from NV- Centers

In this article we present a simple repeater scheme based on the negatively-charged nitrogen vacancy centre in diamond (NV-). Each repeater node is built from simple modules comprising an optical cavity containing a single NV-, with one nuclear spin from 15N as quantum memory. The operation in the module only uses deterministic processes and interactions and achieves high fidelity (>99%) operation, and modules are connected by optical fiber. In the repeater node architecture, the processes between modules by photons can be in principle deterministic, however current limitations on optical components lead to the processes to be probabilistic but heralded. The most resource modest repeater architecture contains at least two modules at each node, and the repeater nodes are than connected by telecom wavelength entangled photon pairs. We discuss the performance of quantum repeaters starting from the minimum-resource strategy with several modules (~10) and then incorporating more resource-intense strategies step by step. Our architecture enables large-scale quantum information networks with existing technology.

quant-ph↗

arXiv2014

Room-temperature near-infrared silicon carbide nanocrystalline emitters based on optically aligned spin defects

Bulk silicon carbide (SiC) is a very promising material system for bio-applications and quantum sensing. However, its optical activity lies beyond the near infrared spectral window for in-vivo imaging and fiber communications due to a large forbidden energy gap. Here, we report the fabrication of SiC nanocrystals and isolation of different nanocrystal fractions ranged from 600 nm down to 60 nm in size. The structural analysis reveals further fragmentation of the smallest nanocrystals into ca. 10-nm-size clusters of high crystalline quality, separated by amorphization areas. We use neutron irradiation to create silicon vacancies, demonstrating near infrared photoluminescence. Finally, we detect, for the first time, room-temperature spin resonances of these silicon vacancies hosted in SiC nanocrystals. This opens intriguing perspectives to use them not only as in-vivo luminescent markers, but also as magnetic field and temperature sensors, allowing for monitoring various physical, chemical and biological processes.

cond-mat.mtrl-sci↗

arXiv2014

Arrays of open, independently tunable microcavities

Optical cavities are of central importance in numerous areas of physics, including precision measurement, cavity optomechanics and cavity quantum electrodynamics. The miniaturisation and scaling to large numbers of sites is of interest for many of these applications, in particular for quantum computation and simulation. Here we present the first scaled microcavity system which enables the creation of large numbers of highly uniform, tunable light-matter interfaces using ions, neutral atoms or solid-state qubits. The microcavities are created by means of silicon micro-fabrication, are coupled directly to optical fibres and can be independently tuned to the chosen frequency, paving the way for arbitrarily large networks of optical microcavities.

quant-ph↗

arXiv2014

Engineering near infrared single photon emitters in ultrapure silicon carbide

Quantum emitters hosted in crystalline lattices are highly attractive candidates for quantum information processing, secure networks and nanosensing. For many of these applications it is necessary to have control over single emitters with long spin coherence times. Such single quantum systems have been realized using quantum dots, colour centres in diamond, dopants in nanostructures and molecules . More recently, ensemble emitters with spin dephasing times on the order of microseconds and room-temperature optically detectable magnetic resonance have been identified in silicon carbide (SiC), a compound being highly compatible to up-to-date semiconductor device technology. So far however, the engineering of such spin centres in SiC on single-emitter level has remained elusive. Here, we demonstrate the control of spin centre density in ultrapure SiC over 8 orders of magnitude, from below $10^{9}$ to above $10^{16} \,$cm$^{-3}$ using neutron irradiation. For a low irradiation dose, a fully photostable, room-temperature, near infrared (NIR) single photon emitter can clearly be isolated, demonstrating no bleaching even after $10^{14}$ excitation cycles. Based on their spectroscopic fingerprints, these centres are identified as silicon vacancies, which can potentially be used as qubits, spin sensors and maser amplifiers.

cond-mat.mtrl-sci↗

arXiv2012

ICP polishing of silicon for high quality optical resonators on a chip

Miniature concave hollows, made by wet etching silicon through a circular mask, can be used as mirror substrates for building optical micro-cavities on a chip. In this paper we investigate how ICP polishing improves both shape and roughness of the mirror substrates. We characterise the evolution of the surfaces during the ICP polishing using white-light optical profilometry and atomic force microscopy. A surface roughness of 1 nm is reached, which reduces to 0.5 nm after coating with a high reflectivity dielectric. With such smooth mirrors, the optical cavity finesse is now limited by the shape of the underlying mirror.

physics.optics↗

arXiv2011

Fast cavity-enhanced atom detection with low noise and high fidelity

Cavity quantum electrodynamics describes the fundamental interactions between light and matter, and how they can be controlled by shaping the local environment. For example, optical microcavities allow high-efficiency detection and manipulation of single atoms. In this regime fluctuations of atom number are on the order of the mean number, which can lead to signal fluctuations in excess of the noise on the incident probe field. Conversely, we demonstrate that nonlinearities and multi-atom statistics can together serve to suppress the effects of atomic fluctuations when making local density measurements on clouds of cold atoms. We measure atom densities below 1 per cavity mode volume near the photon shot-noise limit. This is in direct contrast to previous experiments where fluctuations in atom number contribute significantly to the noise. Atom detection is shown to be fast and efficient, reaching fidelities in excess of 97% after 10 us and 99.9% after 30 us.

quant-ph↗

arXiv2011

Arrays of waveguide-coupled optical cavities that interact strongly with atoms

We describe a realistic scheme for coupling atoms or other quantum emitters with an array of coupled optical cavities. We consider open Fabry-Perot microcavities coupled to the emitters. Our central innovation is to connect the microcavities to waveguide resonators, which are in turn evanescently coupled to each other on a photonic chip to form a coupled cavity chain. In this paper, we describe the components, their technical limitations and the factors that need to be determined experimentally. This provides the basis for a detailed theoretical analysis of two possible experiments to realize quantum squeezing and controlled quantum dynamics. We close with an outline of more advanced applications.

quant-ph↗

arXiv2009

An integrated atom-photon junction

Photonic chips that integrate guides, switches, gratings and other components, process vast amounts of information rapidly on a single device. A new branch of this technology becomes possible if the light is coupled to cold atoms in a junction of small enough cross section, so that small numbers of photons interact appreciably with the atoms. Cold atoms are among the most sensitive of metrological tools and their quantum nature also provides a basis for new information processing methods. Here we demonstrate a photonic chip which provides multiple microscopic junctions between atoms and photons. We use the absorption of light at a junction to reveal the presence of one atom on average. Conversely, we use the atoms to probe the intensity and polarisation of the light. Our device paves the way for a new type of chip with interconnected circuits of atoms and photons.

quant-ph↗

arXiv2009

Atomic Bloch-Zener oscillations for sensitive force measurements in a cavity

Cold atoms in an optical lattice execute Bloch-Zener oscillations when they are accelerated. We have performed a theoretical investigation into the case when the optical lattice is the intra-cavity field of a driven Fabry-Perot resonator. When the atoms oscillate inside the resonator, we find that their back-action modulates the phase and intensity of the light transmitted through the cavity. We solve the coupled atom-light equations self-consistently and show that, remarkably, the Bloch period is unaffected by this back-action. The transmitted light provides a way to observe the oscillation continuously, allowing high precision measurements to be made with a small cloud of atoms.

quant-ph↗