arXiv subjects

Benjamin Pingault

Publications and source records attributed to Benjamin Pingault.

At least 19 recordsLinked to original sources

arXiv2026

Increased cyclicity of atomic transitions via coherent interference of decay paths

Optical readout is a fundamental tool in atomic state measurement, yet the fidelity of optical readout is frequently limited by imperfect photon collection. This can be mitigated when readout occurs on a cycling transition which continuously fluoresces under resonant excitation, thus increasing signal and enabling single-shot readout. We present a method to extend the cyclicity of atomic transitions via coherent destructive interference between spurious decay paths. We describe the characteristics of atomic systems in which this method can be implemented and model several examples in which the number of emitted photons is increased by multiple orders of magnitude.

quant-ph↗

arXiv2026

Spin Dynamics from Atomistic Quantum Simulations

Optically active solid-state spin defects are promising candidates for quantum applications, however a unified theoretical framework to predict their spin dynamics at high temperatures is not yet available. Here, using Kubo linear--response theory, we derive expressions of spin-lattice and decoherence times $T_1$ and $T_2$ in terms of correlation functions of spin--lattice couplings. We then evaluate $T_1$ and $T_2$ from molecular dynamics and spin--lattice interaction time--series generated by state--of--the--art machine learning models trained on {\it ab--initio} data. Finally we measure $T_1$ times for the NV center in diamond and compare experimental and theoretical results, showing excellent agreement.

cond-mat.mtrl-sci↗

arXiv2026

A hybrid quantum network linking telecom-wavelength atomic and solid-state nodes

Photonic links between disparate quantum technologies$-$such as photon sources, memories, processors, clocks, and sensors$-$are key to scaling quantum networks and realizing a versatile quantum internet for secure quantum communication, distributed quantum computing, and entanglement-enhanced metrology. In practice, each technology is most suitably implemented on a different quantum platform; the substantial spectral mismatch between them, along with scarce native telecom interfaces, thus poses a major bottleneck to achieving efficient interconnections over long distances. Here we demonstrate the first deployed two-node hybrid network that operates entirely in the telecom C-band. Our approach uses no quantum frequency conversion or external filtering; instead, we develop a neutral atom single photon source and a solid-state rare-earth quantum memory that both operate in previously unexplored telecom regimes with state-of-the-art performance. The source achieves a high single-photon purity at 46 kcps, and the memory a storage efficiency of 10.6% with high multimode capacity. We leverage the intrinsic tunability of both systems to optimize their spectral overlap and demonstrate microsecond-level storage and retrieval with a large time-bandwidth product. Moreover, we showcase real-world networking competencies such as support for multiplexing across 37 temporal modes and preservation of non-classicality over fibers of 10.6 km (metropolitan) and 49.2 km (laboratory). Our work establishes a backbone for telecom-native quantum repeater links and unlocks a path towards high-bandwidth, large-scale quantum networking.

quant-ph↗

arXiv2025

All-mechanical coherence protection and fast control of a spin qubit

In a phononic quantum network, quantum information is stored and processed within stationary nodes defined by solid-state spins, and the information is routed between nodes by phonons. The phonon holds distinct advantages over its electromagnetic counterpart the photon, including smaller device footprints, reduced crosstalk, long coherence times at low temperatures, and strong interactions with both solid-state spins and electromagnetic waves. Enhanced interactions between a phononic cavity and a stationary qubit have been demonstrated in multiple platforms including superconducting qubits, spins in silicon carbide and spins in diamond. However, an outstanding issue is the compatibility between the spin's coupling to the resonant phononic cavity and the simultaneous use of pulse sequences to extend the coherence time of the spin by suppressing the low-frequency environmental noise. Here we demonstrate all-mechanical coherence protection of a solid-state spin qubit, where optical initialization, quantum operations, and readout are performed in a dressed basis that is highly immune to low-frequency noise and compatible with a phononic cavities. We additionally show record-high Rabi frequencies reaching 800 MHz, which allows for ultrafast quantum control. Our results establish a first step for high-fidelity, phonon-mediated quantum gates and represent a crucial advance toward robust on-chip quantum phononic networks.

quant-ph↗

arXiv2025

Thin Film Lithium Niobate on Diamond (LiNDa) platform for Efficient Spin-Phonon Coupling

Negatively charged silicon vacancy (SiV) center in diamonds are leading candidates for solid-state quantum memories that can be controlled using electromagnetic or acoustic waves. The latter are particularly promising due to strong strain response of SiV, enabling large spin-phonon interaction strengths. Indeed, coherent spin control via surface acoustic waves (SAW) has been demonstrated and is essential for developing on-chip phononic quantum networks. However, the absence of piezoelectricity in diamond requires interfacing with a piezoelectric material for efficient transduction and delivery of acoustic waves to spins in diamonds. Here, we demonstrate a heterogeneously integrated phononic platform that combines thin-film lithium niobate (TFLN) with diamond to enable acoustic control of single SiV spins. Additionally, leveraging large SAW-induced strain at the location of SiV, we achieve coherent acoustic control of an electron spin with more than twofold improvement in Rabi frequency compared to the state-of-the-art devices based on aluminum nitride-on-diamond. This work represents a crucial step towards realizing phonon-based quantum information processing systems.

quant-ph↗

arXiv2025

Minute-long quantum coherence enabled by electrical depletion of magnetic noise

Integrating solid-state spin defects into classical electronic devices can enable new opportunities for quantum information processing that benefit from existing semiconductor technology. Here, we investigate the impact of bias control of an isotopically purified silicon carbide (SiC) p-i-n diode on the coherence of embedded spins. We show that the diode allows for the depletion of not only the electrical, but also the magnetic noise sources. This results in extended relaxation and coherence times of individual electronic and nuclear spins, with Hahn echo times exceeding values reported for single spins in any platform (> 100 seconds). These results demonstrate the importance of materials control and electronic device integration to create highly coherent solid-state quantum technology.

quant-ph↗

arXiv2025

Purcell-enhanced spin-phonon coupling with a single color center

The radiative properties of atoms are inherently linked to their surrounding environment. Placing an electromagnetic resonator around atoms can enhance spontaneous emission, as shown by Purcell in the 1940s. This approach is now routinely used in quantum computing and communication to channel photons emitted by atoms into well-defined modes and control atom-photon interactions. For solid-state artificial atoms, such as color-centers, the host lattice introduces an acoustic environment, allowing excited atoms to relax by emitting phonons. Here we observe the acoustic Purcell effect by constructing a specially engineered, microwave-frequency nanomechanical resonator around a color-center spin qubit in diamond. Using a co-localized optical mode of the structure that strongly couples to the color-center's excited state, we perform single-photon-level laser spectroscopy at milliKelvin temperatures and observe ten-fold faster spin relaxation when the spin qubit is tuned into resonance with a 12 GHz acoustic mode. Additionally, we use the color-center as an atomic-scale probe to measure the broadband phonon spectrum of the nanostructure up to a frequency of 28 GHz. Our work establishes a new regime of control for quantum defects in solids and paves the way for interconnects between atomic-scale quantum memories and qubits encoded in acoustic and superconducting devices.

quant-ph↗

arXiv2025

First-Principles Framework for the Prediction of Intersystem Crossing Rates in Spin Defects: The Role of Electron Correlation

Optically active spin defects in solids are promising platforms for quantum technologies. Here, we present a first-principles framework to investigate intersystem crossing processes, which represent crucial steps in the optical spin-polarization cycle used to address spin defects. Considering the nitrogen-vacancy center in diamond as a case study, we demonstrate that our framework effectively captures electron correlation effects in the calculation of many-body electronic states and their spin-orbit coupling and electron-phonon interactions, while systematically addressing finite-size effects. We validate our predictions by carrying out measurements of fluorescence lifetimes, finding excellent agreement between theory and experiments. The framework presented here provides a versatile and robust tool for exploring the optical cycle of varied spin defects entirely from first principles.

cond-mat.mtrl-sci↗

arXiv2025

Nuclear Spin Engineering for Quantum Information Science

Semiconductors are the backbone of modern technology, garnering decades of investment in high quality materials and devices. Electron spin systems in semiconductors, including atomic defects and quantum dots, have been demonstrated in the last two decades to host quantum coherent spin qubits, often with coherent spin-photon interfaces and proximal nuclear spins. These systems are at the center of developing quantum technology. However, new material challenges arise when considering the isotopic composition of host and qubit systems. The isotopic composition governs the nature and concentration of nuclear spins, which naturally occur in leading host materials. These spins generate magnetic noise -- detrimental to qubit coherence -- but also show promise as local quantum memories and processors, necessitating careful engineering dependent on the targeted application. Reviewing recent experimental and theoretical progress towards understanding local nuclear spin environments in semiconductors, we show this aspect of material engineering as critical to quantum information technology.

quant-ph↗

arXiv2023

High Q-factor diamond optomechanical resonators with silicon vacancy centers at millikelvin temperatures

Phonons are envisioned as coherent intermediaries between different types of quantum systems. Engineered nanoscale devices such as optomechanical crystals (OMCs) provide a platform to utilize phonons as quantum information carriers. Here we demonstrate OMCs in diamond designed for strong interactions between phonons and a silicon vacancy (SiV) spin. Using optical measurements at millikelvin temperatures, we measure a linewidth of 13 kHz (Q-factor of ~440,000) for 6 GHz acoustic modes, a record for diamond in the GHz frequency range and within an order of magnitude of state-of-the-art linewidths for OMCs in silicon. We investigate SiV optical and spin properties in these devices and outline a path towards a coherent spin-phonon interface.

physics.optics↗

arXiv2023

Engineering Phonon-Qubit Interactions using Phononic Crystals

The ability to control phonons in solids is key for diverse quantum applications, ranging from quantum information processing to sensing. Often, phonons are sources of noise and decoherence, since they can interact with a variety of solid-state quantum systems. To mitigate this, quantum systems typically operate at milli-Kelvin temperatures to reduce the number of thermal phonons. Here we demonstrate an alternative approach that relies on engineering phononic density of states, drawing inspiration from photonic bandgap structures that have been used to control the spontaneous emission of quantum emitters. We design and fabricate diamond phononic crystals with a complete phononic bandgap spanning 50 - 70 gigahertz, tailored to suppress interactions of a single silicon-vacancy color center with resonant phonons of the thermal bath. At 4 Kelvin, we demonstrate a reduction of the phonon-induced orbital relaxation rate of the color center by a factor of 18 compared to bulk. Furthermore, we show that the phononic bandgap can efficiently suppress phonon-color center interactions up to 20 Kelvin. In addition to enabling operation of quantum memories at higher temperatures, the ability to engineer qubit-phonon interactions may enable new functionalities for quantum science and technology, where phonons are used as carriers of quantum information.

quant-ph↗

arXiv2023

Integrated Phononic Waveguides in Diamond

Efficient generation, guiding, and detection of phonons, or mechanical vibrations, are of interest in various fields including radio frequency communication, sensing, and quantum information. Diamond is an important platform for phononics because of the presence of strain-sensitive spin qubits, and its high Young's modulus which allows for low-loss gigahertz devices. We demonstrate a diamond phononic waveguide platform for generating, guiding, and detecting gigahertz-frequency surface acoustic wave (SAW) phonons. We generate SAWs using interdigital transducers integrated on AlN/diamond and observe SAW transmission at 4-5 GHz through both ridge and suspended waveguides, with wavelength-scale cross sections (~1 {\mu}m2) to maximize spin-phonon interaction. This work is a crucial step for developing acoustic components for quantum phononic circuits with strain-sensitive color centers in diamond.

physics.app-ph↗

arXiv2023

Microwave-based quantum control and coherence protection of tin-vacancy spin qubits in a strain-tuned diamond membrane heterostructure

Robust spin-photon interfaces in solids are essential components in quantum networking and sensing technologies. Ideally, these interfaces combine a long-lived spin memory, coherent optical transitions, fast and high-fidelity spin manipulation, and straightforward device integration and scaling. The tin-vacancy center (SnV) in diamond is a promising spin-photon interface with desirable optical and spin properties at 1.7 K. However, the SnV spin lacks efficient microwave control and its spin coherence degrades with higher temperature. In this work, we introduce a new platform that overcomes these challenges - SnV centers in uniformly strained thin diamond membranes. The controlled generation of crystal strain introduces orbital mixing that allows microwave control of the spin state with 99.36(9) % gate fidelity and spin coherence protection beyond a millisecond. Moreover, the presence of crystal strain suppresses temperature dependent dephasing processes, leading to a considerable improvement of the coherence time up to 223(10) ${\mu}$s at 4 K, a widely accessible temperature in common cryogenic systems. Critically, the coherence of optical transitions is unaffected by the elevated temperature, exhibiting nearly lifetime-limited optical linewidths. Combined with the compatibility of diamond membranes with device integration, the demonstrated platform is an ideal spin-photon interface for future quantum technologies.

cond-mat.mes-hall↗

arXiv2023

Proposal for a distributed, community-driven academic publishing system

We propose an academic publishing system where research papers are stored in a network of data centres owned by university libraries and research institutions, and are interfaced with the academic community through a website. In our system, the editor is replaced by an initial adjusted community-wide evaluation, the standard peer-review is accompanied by a post-publication open-ended and community-wide review process, aiming at a more objective and longer-term evaluation, the publishing costs are reduced to the running costs of the servers, and access is fully open. Our proposal addresses the fundamental problems of the current system: it reduces publishing costs, allowing easier access by less well-funded institutions (especially from developing countries); it makes the editorial evaluation distributed and more transparent; it speeds up the peer review process by eliminating the need for multiple resubmissions; and it introduces a long-term, community-wide evaluation of papers, ensuring their continued relevance and accuracy; while maximising its main goals, i.e. ensuring the highest quality of peer review and giving the best referees, the most visibility and the most credit to the best papers. Our scheme is time-efficient, financially sustainable, ethically fair and represents a significant improvement over the current system.

cs.DL↗

arXiv2022

Robust multi-qubit quantum network node with integrated error detection

Long-distance quantum communication and networking require quantum memory nodes with efficient optical interfaces and long memory times. We report the realization of an integrated two-qubit network node based on silicon-vacancy centers (SiVs) in diamond nanophotonic cavities. Our qubit register consists of the SiV electron spin acting as a communication qubit and the strongly coupled 29Si nuclear spin acting as a memory qubit with a quantum memory time exceeding two seconds. By using a highly strained SiV with suppressed electron spin-phonon interactions, we realize electron-photon entangling gates at elevated temperatures up to 1.5 K and nucleus-photon entangling gates up to 4.3 K. Finally, we demonstrate efficient error detection in nuclear spin-photon gates by using the electron spin as a flag qubit, making this platform a promising candidate for scalable quantum repeaters.

quant-ph↗

arXiv2022

Sensing the local magnetic environment through optically active defects in a layered magnetic semiconductor

Atomic-level defects in van der Waals (vdW) materials are essential building blocks for quantum technologies and quantum sensing applications. The layered magnetic semiconductor CrSBr is an outstanding candidate for exploring optically active defects owing to a direct gap in addition to a rich magnetic phase diagram including a recently hypothesized defect-induced magnetic order at low temperature. Here, we show optically active defects in CrSBr that are probes of the local magnetic environment. We observe spectrally narrow (1 meV) defect emission in CrSBr that is correlated with both the bulk magnetic order and an additional low temperature defect-induced magnetic order. We elucidate the origin of this magnetic order in the context of local and non-local exchange coupling effects. Our work establishes vdW magnets like CrSBr as an exceptional platform to optically study defects that are correlated with the magnetic lattice. We anticipate that controlled defect creation allows for tailor-made complex magnetic textures and phases with the unique ingredient of direct optical access.

cond-mat.mes-hall↗

arXiv2022

The bulk van der Waals layered magnet CrSBr is a quasi-1D material

Correlated quantum phenomena in one-dimensional (1D) systems that exhibit competing electronic and magnetic order are of strong interest for studying fundamental interactions and excitations, such as Tomonaga-Luttinger liquids and topological orders and defects with properties completely different from the quasiparticles expected in their higher-dimensional counterparts. However, clean 1D electronic systems are difficult to realize experimentally, particularly magnetically ordered systems. Here, we show that the van der Waals layered magnetic semiconductor CrSBr behaves like a quasi-1D material embedded in a magnetically ordered environment. The strong 1D electronic character originates from the Cr-S chains and the combination of weak interlayer hybridization and anisotropy in effective mass and dielectric screening with an effective electron mass ratio of $m^e_X/m^e_Y \sim 50$. This extreme anisotropy experimentally manifests in strong electron-phonon and exciton-phonon interactions, a Peierls-like structural instability and a Fano resonance from a van Hove singularity of similar strength of metallic carbon nanotubes. Moreover, due to the reduced dimensionality and interlayer coupling, CrSBr hosts spectrally narrow (1 meV) excitons of high binding energy and oscillator strength that inherit the 1D character. Overall, CrSBr is best understood as a stack of weakly hybridized monolayers and appears to be an experimentally attractive candidate for the study of exotic exciton and 1D correlated many-body physics in the presence of magnetic order.

cond-mat.mes-hall↗

arXiv2021

Coherent coupling of mechanics to a single nuclear spin

Nuclear spins interact weakly with their environment. In particular, they are generally insensitive to mechanical vibrations. Here, we successfully demonstrate the coherent coupling of mechanics to a single nuclear spin. This coupling is mediated by a silicon vacancy (SiV) centre in diamond, taking advantage of its large strain susceptibility and hyperfine interaction with nuclear spins. Importantly, we demonstrate that the nuclear spin retains its excellent coherence properties even in the presence of this coupling. This provides a way to leverage nuclear spins as quantum memories for mechanical systems in the quantum regime.

quant-ph↗