arXiv subjects

A. Dréau

Publications and source records attributed to A. Dréau.

17 recordsLinked to original sources

arXiv2022

Cavity-enhanced zero-phonon emission from an ensemble of G centers in a silicon-on-insulator microring

We report successful incorporation of an ensemble of G centers in silicon-on-insulator (SOI) microrings using ion implantation and conventional nanofabrication. The coupling between the emitters and the resonant modes of the microrings is studied using continuous-wave and time-resolved microphotoluminescence (PL) experiments. We observe the resonant modes of the microrings on PL spectra, on the wide spectral range that is covered by G centers emission. By finely tuning the size of the microrings, we match their zero-phonon line at 1278 nm with a resonant mode of quality factor around 3000 and volume 7.2 (lambda over n)^3. The zero-phonon line intensity is enhanced by a factor of 5, both in continuous-wave and time-resolved measurements. This is attributed to the Purcell enhancement of zero-phonon spontaneous emission into the resonant mode and quantitatively understood considering the distribution of the G centers dipoles. Despite the enhancement of the zero-phonon emission, we do not observe any sizeable decrease of the average lifetime of the G centers, which points at a low radiative yield (<10%). We reveal the detrimental impact of parasitic defects in heavily implanted silicon, and discuss the perspectives for quantum electrodynamics experiments with individual color centers in lightly implanted SOI rings. Our results provide key information for the development of deterministic single photon sources for integrated quantum photonics.

physics.optics↗

arXiv2021

Decoherence of V$_{\rm B}^{-}$ spin defects in monoisotopic hexagonal boron nitride

Spin defects in hexagonal boron nitride (hBN) are promising quantum systems for the design of flexible two-dimensional quantum sensing platforms. Here we rely on hBN crystals isotopically enriched with either $^{10}$B or $^{11}$B to investigate the isotope-dependent properties of a spin defect featuring a broadband photoluminescence signal in the near infrared. By analyzing the hyperfine structure of the spin defect while changing the boron isotope, we first unambiguously confirm that it corresponds to the negatively-charged boron-vacancy center (${\rm V}_{\rm B}^-$). We then show that its spin coherence properties are slightly improved in $^{10}$B-enriched samples. This is supported by numerical simulations employing cluster correlation expansion methods, which reveal the importance of the hyperfine Fermi contact term for calculating the coherence time of point defects in hBN. Using cross-relaxation spectroscopy, we finally identify dark electron spin impurities as an additional source of decoherence. This work provides new insights into the properties of ${\rm V}_{\rm B}^-$ spin defects, which are valuable for the future development of hBN-based quantum sensing foils.

cond-mat.mtrl-sci↗

arXiv2020

Broad diversity of near-infrared single-photon emitters in silicon

We report the detection of individual emitters in silicon belonging to seven different families of optically-active point defects. These fluorescent centers are created by carbon implantation of a commercial silicon-on-insulator wafer usually employed for integrated photonics. Single photon emission is demonstrated over the [1.1,1.55]-$μ$m range, spanning the O- and C-telecom bands. We analyse their photoluminescence spectrum, dipolar emission and optical relaxation dynamics at 10K. For a specific family, we show a constant emission intensity at saturation from 10K to temperatures well above the 77K-liquid nitrogen temperature. Given the advanced control over nanofabrication and integration in silicon, these novel artificial atoms are promising candidates for Si-based quantum technologies.

quant-ph↗

arXiv2020

Optimal architecture for diamond-based wide-field thermal imaging

Nitrogen-Vacancy centers in diamond possess an electronic spin resonance that strongly depends on temperature, which makes them efficient temperature sensor with a sensitivity down to a few mK/$\sqrt{\rm Hz}$. However, the high thermal conductivity of the host diamond may strongly damp any temperature variations, leading to invasive measurements when probing local temperature distributions. In view of determining possible and optimal configurations for diamond-based wide-field thermal imaging, we here investigate, both experimentally and numerically, the effect of the presence of diamond on microscale temperature distributions. Three geometrical configurations are studied: a bulk diamond substrate, a thin diamond layer bonded on quartz and diamond nanoparticles dispersed on quartz. We show that the use of bulk diamond substrates for thermal imaging is highly invasive, in the sense that it prevents any substantial temperature increase. Conversely, thin diamond layers partly solve this issue and could provide a possible alternative for microscale thermal imaging. Dispersions of diamond nanoparticles throughout the sample appear as the most relevant approach as they do not affect the temperature distribution, although NV centers in nanodiamonds yield lower temperature sensitivities compared to bulk diamond.

physics.app-ph↗

arXiv2020

Single artificial atoms in silicon emitting at telecom wavelengths

Given its unrivaled potential of integration and scalability, silicon is likely to become a key platform for large-scale quantum technologies. Individual electron-encoded artificial atoms either formed by impurities or quantum dots have emerged as a promising solution for silicon-based integrated quantum circuits. However, single qubits featuring an optical interface needed for large-distance exchange of information have not yet been isolated in such a prevailing semiconductor. Here we show the isolation of single optically-active point defects in a commercial silicon-on-insulator wafer implanted with carbon atoms. These artificial atoms exhibit a bright, linearly polarized single-photon emission at telecom wavelengths suitable for long-distance propagation in optical fibers. Our results demonstrate that despite its small bandgap (~ 1.1 eV) a priori unfavorable towards such observation, silicon can accommodate point defects optically isolable at single scale, like in wide-bandgap semiconductors. This work opens numerous perspectives for silicon-based quantum technologies, from integrated quantum photonics to quantum communications and metrology.

physics.app-ph↗

arXiv2018

Optimizing synthetic diamond samples for quantum sensing technologies by tuning the growth temperature

Control of the crystalline orientation of nitrogen-vacancy (NV) defects in diamond is here demonstrated by tuning the temperature of chemical vapor deposition (CVD) growth on a (113)-oriented diamond substrate. We show that preferential alignment of NV defects along the [111] axis is significantly improved when the CVD growth temperature is decreased. This effect is then combined with temperature-dependent incorporation of NV defects during the CVD growth to obtain preferential alignment over dense ensembles of NV defects spatially localized in thin diamond layers. These results demonstrate that growth temperature can be exploited as an additional degree of freedom to engineer optimized diamond samples for quantum sensing applications.

cond-mat.mtrl-sci↗

arXiv2016

Loophole-free Bell test using electron spins in diamond: second experiment and additional analysis

The recently reported violation of a Bell inequality using entangled electronic spins in diamonds (Hensen et al., Nature 526, 682-686) provided the first loophole-free evidence against local-realist theories of nature. Here we report on data from a second Bell experiment using the same experimental setup with minor modifications. We find a violation of the CHSH-Bell inequality of $2.35 \pm 0.18$, in agreement with the first run, yielding an overall value of $S = 2.38 \pm 0.14$. We calculate the resulting $P$-values of the second experiment and of the combined Bell tests. We provide an additional analysis of the distribution of settings choices recorded during the two tests, finding that the observed distributions are consistent with uniform settings for both tests. Finally, we analytically study the effect of particular models of random number generator (RNG) imperfection on our hypothesis test. We find that the winning probability per trial in the CHSH game can be bounded knowing only the mean of the RNG bias, implying that our experimental result is robust for any model underlying the estimated average RNG bias.

quant-ph↗

arXiv2015

Competition between electric field and magnetic field noise in the decoherence of a single spin in diamond

We analyze the impact of electric field and magnetic field fluctuations in the decoherence of the electronic spin associated with a single nitrogen-vacancy (NV) defect in diamond by engineering spin eigenstates protected either against magnetic noise or against electric noise. The competition between these noise sources is analyzed quantitatively by changing their relative strength through modifications of the environment. This study provides significant insights into the decoherence of the NV electronic spin, which is valuable for quantum metrology and sensing applications.

cond-mat.mes-hall↗

arXiv2015

Coherent population trapping of a single nuclear spin under ambient conditions

Coherent control of quantum systems has far-reaching implications in quantum engineering. In this context, coherent population trapping (CPT) involving dark resonances has played a prominent role, leading to a wealth of major applications including laser cooling of atoms and molecules, optical magnetometry, light storage and highly precise atomic clocks. Extending CPT methods to individual solid-state quantum systems has been only achieved in cryogenic environments for electron spin impurities and superconducting circuits. Here, we demonstrate efficient CPT of a single nuclear spin in a room temperature solid. To this end, we make use of a three-level system with a $Λ$-configuration in the microwave domain, which consists of nuclear spin states addressed through their hyperfine coupling to the electron spin of a single nitrogen-vacancy defect in diamond. Dark state pumping requires a relaxation mechanism which, in atomic systems, is simply provided by spontaneous emission. In this work, the relaxation process is externally controlled through incoherent optical pumping and separated in time from consecutive coherent microwave excitations of the nuclear spin $Λ$-system. Such a pumping scheme with controlled relaxation allows us (i) to monitor the sequential accumulation of population into the dark state and (ii) to reach a new regime of CPT dynamics for which periodic arrays of dark resonances can be observed, owing to multiple constructive interferences. This work offers new prospects for quantum state preparation, information storage in hybrid quantum systems and metrology.

quant-ph↗

arXiv2014

Probing the dynamics of a nuclear spin bath in diamond through time-resolved central spin magnetometry

Using fast electron spin resonance spectroscopy of a single nitrogen-vacancy defect in diamond, we demonstrate real-time readout of the Overhauser field produced by its nuclear spin environment under ambient conditions. These measurements enable narrowing the Overhauser field distribution by post-selection, corresponding to a conditional preparation of the nuclear spin bath. Correlations of the Overhauser field fluctuations are quantitatively inferred by analysing the Allan deviation over consecutive measurements. This method allows to extract the dynamics of weakly coupled nuclear spins of the reservoir.

cond-mat.mes-hall↗

arXiv2012

Single-shot readout of multiple nuclear spin qubits in diamond under ambient conditions

We use the electronic spin of a single Nitrogen-Vacancy (NV) defect in diamond to observe the real-time evolution of neighboring single nuclear spins under ambient conditions. Using a diamond sample with a natural abundance of $^{13}$C isotopes, we first demonstrate high fidelity initialization and single-shot readout of an individual $^{13}$C nuclear spin. By including the intrinsic $^{14}$N nuclear spin of the NV defect in the quantum register, we then report the simultaneous observation of quantum jumps linked to both nuclear spin species, providing an efficient initialization of the two qubits. These results open up new avenues for diamond-based quantum information processing including active feedback in quantum error correction protocols and tests of quantum correlations with solid-state single spins at room temperature.

quant-ph↗

arXiv2012

Electron spin resonance detected by a superconducting qubit

A new method for detecting the magnetic resonance of electronic spins at low temperature is demonstrated. It consists in measuring the signal emitted by the spins with a superconducting qubit that acts as a single-microwave-photon detector, resulting in an enhanced sensitivity. We implement this new type of electron-spin resonance spectroscopy using a hybrid quantum circuit in which a transmon qubit is coupled to a spin ensemble consisting of NV centers in diamond. With this setup we measure the NV center absorption spectrum at 30mK at an excitation level of \thicksim15\,μ_{B} out of an ensemble of 10^{11} spins.

quant-ph↗

arXiv2012

High resolution spectroscopy of single NV defects coupled with nearby $^{13}$C nuclear spins in diamond

We report a systematic study of the hyperfine interaction between the electron spin of a single nitrogen-vacancy (NV) defect in diamond and nearby $^{13}$C nuclear spins, by using pulsed electron spin resonance spectroscopy. We isolate a set of discrete values of the hyperfine coupling strength ranging from 14 MHz to 400 kHz and corresponding to $^{13}$C nuclear spins placed at different lattice sites of the diamond matrix. For each lattice site, the hyperfine interaction is further investigated through nuclear spin polarization measurements and by studying the magnetic field dependence of the hyperfine splitting. This work provides informations that are relevant for the development of nuclear-spin based quantum register in diamond.

cond-mat.mes-hall↗

arXiv2012

Avoiding power broadening in optically detected magnetic resonance of single NV defects for enhanced DC-magnetic field sensitivity

We report a systematic study of the magnetic field sensitivity of a magnetic sensor based on a single Nitrogen-Vacancy (NV) defect in diamond, by using continuous optically detected electron spin resonance (ESR) spectroscopy. We first investigate the behavior of the ESR contrast and linewidth as a function of the microwave and optical pumping power. The experimental results are in good agreement with a simplified model of the NV defect spin dynamics, yielding to an optimized sensitivity around 2 μT/\sqrt{\rm Hz}. We then demonstrate an enhancement of the magnetic sensitivity by one order of magnitude by using a simple pulsed-ESR scheme. This technique is based on repetitive excitation of the NV defect with a resonant microwave π-pulse followed by an optimized read-out laser pulse, allowing to fully eliminate power broadening of the ESR linewidth. The achieved sensitivity is similar to the one obtained by using Ramsey-type sequences, which is the optimal magnetic field sensitivity for the detection of DC magnetic fields.

cond-mat.mes-hall↗

arXiv2011

Hybrid quantum circuit with a superconducting qubit coupled to a spin ensemble

We report the experimental realization of a hybrid quantum circuit combining a superconducting qubit and an ensemble of electronic spins. The qubit, of the transmon type, is coherently coupled to the spin ensemble consisting of nitrogen-vacancy (NV) centers in a diamond crystal via a frequency-tunable superconducting resonator acting as a quantum bus. Using this circuit, we prepare arbitrary superpositions of the qubit states that we store into collective excitations of the spin ensemble and retrieve back later on into the qubit. These results constitute a first proof of concept of spin-ensemble based quantum memory for superconducting qubits.

quant-ph↗

arXiv2010

Strong Coupling of a Spin Ensemble to a Superconducting Resonator

We report the realization of a quantum circuit in which an ensemble of electronic spins is coupled to a frequency tunable superconducting resonator. The spins are Nitrogen-Vacancy centers in a diamond crystal. The achievement of strong coupling is manifested by the appearance of a vacuum Rabi splitting in the transmission spectrum of the resonator when its frequency is tuned through the NV center electron spin resonance.

cond-mat.supr-con↗

arXiv2010

Engineered arrays of NV color centers in diamond based on implantation of CN- molecules through nanoapertures

We report a versatile method to engineer arrays of nitrogen-vacancy (NV) color centers in dia- mond at the nanoscale. The defects were produced in parallel by ion implantation through 80 nm diameter apertures patterned using electron beam lithography in a PMMA layer deposited on a diamond surface. The implantation was performed with CN- molecules which increased the NV defect formation yield. This method could enable the realization of a solid-state coupled-spin array and could be used for positioning an optically active NV center on a photonic microstructure.

quant-ph↗