Towards continuous-wave regime teleportation for light matter quantum relay stations

We report a teleportation experiment involving narrowband entangled photons at 1560 nm and qubit photons at 795 nm emulated by faint laser pulses. A nonlinear difference frequency generation stage converts the 795 nm photons to 1560 nm in order to enable interference with one photon out of the pairs, i.e., at the same wavelength. The spectral bandwidth of all involved photons is of about 25 MHz, which is close to the emission bandwidth of emissive quantum memory devices, notably those based on ensembles of cold atoms and rare earth ions. This opens the route towards the realization of hybrid quantum nodes, i.e., combining quantum memories and entanglement-based quantum relays exploiting either a synchronized (pulsed) or asynchronous (continuous- wave) scenario

Resonant versus non-resonant spin readout of a nitrogen-vacancy center in diamond under cryogenic conditions

The last decade has seen an explosive growth in the use of color centers for metrology applications, the paradigm example arguably being the nitrogen-vacancy (NV) center in diamond. Here, we focus on the regime of cryogenic temperatures and examine the impact of spin-selective, narrow-band laser excitation on NV readout. Specifically, we demonstrate a more than four-fold improvement in sensitivity compared to that possible with non-resonant (green) illumination, largely due to a boost in readout contrast and integrated photon count. We also leverage nuclear spin relaxation under resonant excitation to polarize the 14N host, which we then prove beneficial for spin magnetometry. These results open opportunities in the application of NV sensing to the investigation of condensed matter systems, particularly those exhibiting superconducting, magnetic, or topological phases selectively present at low temperatures

Spin Read-out of the Motion of Levitated Electrically Rotated Diamonds

Recent advancements with trapped nano- and micro-particles have enabled the exploration of motional states on unprecedented scales. Rotational degrees of freedom stand out due to their intrinsic non-linearity and their coupling with internal spin degrees of freedom, opening up possibilities for gyroscopy and magnetometry applications and the creation of macroscopic quantum superpositions. However, current techniques for fast and reliable rotation of particles with internal spins face challenges, such as optical absorption and heating issues. Here, to address this gap, we demonstrate electrically driven rotation of micro-particles levitating in Paul traps. We show that micro-particles can be set to rotate stably at 150,000 rpm by operating in a hitherto unexplored parametrically driven regime using the particle electric quadrupolar moment. Moreover, the spin states of nitrogen-vacancy centers in diamonds undergoing full rotation were successfully controlled, allowing accurate angular trajectory reconstruction and demonstrating high rotational stability over extended periods. These achievements mark progress toward interfacing full rotation with internal magnetic degrees of freedom in micron-scale objects. In particular, it extends significantly the type of particles that can be rotated, such as ferromagnets, which offers direct implications for the study of large gyromagnetic effects at the micro-scale

Spin dynamics of a solid-state qubit in proximity to a superconductor

A broad effort is underway to understand and harness the interaction between superconductors and spin-active color centers with an eye on the realization of hybrid quantum devices and novel imaging modalities of superconducting materials. Most work, however, overlooks the complex interplay between either system and the environment created by the color center host. Here we use an all-diamond scanning probe to investigate the spin dynamics of a single nitrogen-vacancy (NV) center proximal to a high-critical-temperature superconducting film in the presence of a weak magnetic field. We find that the presence of the superconductor increases the NV spin coherence lifetime, a phenomenon we tentatively rationalize as a change in the electric noise due to a superconductor-induced redistribution of charge carriers near the NV site. We build on these findings to demonstrate transverse-relaxation-time-weighted imaging of the superconductor film. These results shed light on the complex surface dynamics governing the spin coherence of shallow NVs while simultaneously paving the route to new forms of noise spectroscopy and imaging of superconductors

A Multicenter, Randomized, Placebo‐Controlled Trial of Atorvastatin for the Primary Prevention of Cardiovascular Events in Patients With Rheumatoid Arthritis

Objective: Rheumatoid arthritis (RA) is associated with increased cardiovascular event (CVE) risk. The impact of statins in RA is not established. We assessed whether atorvastatin is superior to placebo for the primary prevention of CVEs in RA patients. Methods: A randomized, double‐blind, placebo‐controlled trial was designed to detect a 32% CVE risk reduction based on an estimated 1.6% per annum event rate with 80% power at P 50 years or with a disease duration of >10 years who did not have clinical atherosclerosis, diabetes, or myopathy received atorvastatin 40 mg daily or matching placebo. The primary end point was a composite of cardiovascular death, myocardial infarction, stroke, transient ischemic attack, or any arterial revascularization. Secondary and tertiary end points included plasma lipids and safety. Results: A total of 3,002 patients (mean age 61 years; 74% female) were followed up for a median of 2.51 years (interquartile range [IQR] 1.90, 3.49 years) (7,827 patient‐years). The study was terminated early due to a lower than expected event rate (0.70% per annum). Of the 1,504 patients receiving atorvastatin, 24 (1.6%) experienced a primary end point, compared with 36 (2.4%) of the 1,498 receiving placebo (hazard ratio [HR] 0.66 [95% confidence interval (95% CI) 0.39, 1.11]; P = 0.115 and adjusted HR 0.60 [95% CI 0.32, 1.15]; P = 0.127). At trial end, patients receiving atorvastatin had a mean ± SD low‐density lipoprotein (LDL) cholesterol level 0.77 ± 0.04 mmoles/liter lower than those receiving placebo (P < 0.0001). C‐reactive protein level was also significantly lower in the atorvastatin group than the placebo group (median 2.59 mg/liter [IQR 0.94, 6.08] versus 3.60 mg/liter [IQR 1.47, 7.49]; P < 0.0001). CVE risk reduction per mmole/liter reduction in LDL cholesterol was 42% (95% CI −14%, 70%). The rates of adverse events in the atorvastatin group (n = 298 [19.8%]) and placebo group (n = 292 [19.5%]) were similar. Conclusion: Atorvastatin 40 mg daily is safe and results in a significantly greater reduction of LDL cholesterol level than placebo in patients with RA. The 34% CVE risk reduction is consistent with the Cholesterol Treatment Trialists’ Collaboration meta‐analysis of statin effects in other populations

Micro-particules en lévitation dans un piège de Paul pour la spin-mécanique

Inspired by experiments on cold atoms and ions, the field optomechanics has made major steps towards realizing quantum mechanical experiments with macroscopic mechanical oscillators. Hybrid systems such as the spin of Nitrogen Vacancy (NV) centers coupled to a mechanical oscillator levitating under vacuum offer another promising approach. In this work, we levitate microdiamonds with ensembles of embedded NV spins and explore effects related to the coupling between the NV spins and the libration (angular oscillations) of the micro-diamonds.Levitation is carried out by a Paul trap, which confines both the center of mass and angular degrees of freedom of a charged micro-diamond. In a first set of experiments, we demonstrate angular stability using NV spins and perform spin echoes with levitating diamond, showing no detectable impact of the trapping mechanism on the NV spins coherence and lifetime.We then use highly doped diamonds with large NV spins ensembles to exert a spin-dependent torque on a levitating micro-diamond. Observation of an NV spin-induced torque on a mechanical oscillator offers many prospects, such as controlling the mechanical oscillator in the quantum regime, spin-spin coupling or room temperature quantum non-destructive read-out, in the single spin limit. Here the most direct application is the use of these ensembles to apply a non-conservative back-action on the angular motion of the diamond. This results in cooling or amplification of the librational modes of the diamond.The main limitation of the current system is the low mechanical frequencies compared to the NV spins decoherence rate. To leverage this issue we levitate both ferromagnetic and composite ferromagnetic-diamond particles. We show one can use the magnetic moment of these particles to gain two order of magnitude in confinement for the angular degree of freedom, putting the mechanical frequencies higher than NV spins decoherence rate in high-purity diamond samples.Inspiré des expériences d’atomes froids ou d’ions piégés, l’opto-mécanique a réalisé d’important progrès vers des expériences de mécanique quantique avec un oscillateur mécanique macroscopique. Une autre approche prometteuse est l'utilisation de systèmes hybrides ou le couplage entre un atome et un oscillateur mécanique permet le contrôle cohérent de ce dernier.Dans ce travail, les modes de librations (oscillation angulaire) de micro-diamants en lévitation constituent l'oscillateur mécanique. Celui-ci est couplé via un champ magnétique aux spins de centre azote-lacune (NV) contenu dans le micro-diamant. Ce couplage permet alors le refroidissement du mouvement du micro-diamant, similairement à ce qui a pu être fait avec le mouvement d'ions ou d'atomes piégés.La lévitation est réalisée à l’aide d’un piège de Paul qui confine le centre de masse mais également les degrés de liberté angulaire d’un micro-diamant chargé. Lors des premières expériences, nous utilisons les centres NV pour démontrer la stabilité angulaire et montrons que leurs propriétés de spin (cohérence, temps de vie) ne sont pas affectées par le piège.Nous lévitons ensuite des diamants hautement dopés contenant un grand nombre de centres NV et utilisons leur spin pour exercer un couple sur le micro-diamant en lévitation. L’observation de ce couple ouvre de nombreuses perspectives telles que le contrôle de l’oscillateur mécanique dans le régime quantique, le couplage spin-spin et la mesure non-destructive d’un spin NV à température ambiante dans la limite du spin unique. Ici l’application la plus directe de cet effet est l’utilisation de ces ensembles de spins pour exercer une rétroaction non-conservative sur le mouvement angulaire du diamant. Cela résulte en un refroidissement ou une amplification du mode de libration du diamant.La principale limitation du système est la faiblesse des fréquences de l’oscillateur mécanique comparées au taux de décohérence des spins des centres NV. Pour résoudre ce problème, nous lévitons des particules ferromagnétiques ainsi que des particules composites ferromagnétique-diamant. Nous montrons que le moment magnétique de ces particules peut être utilisé pour augmenter le confinement angulaire de deux ordres de grandeur, plaçant ainsi les fréquences de l’oscillateur mécanique au-delà des taux de décohérences typique de centres NV dans des diamants ultra-pures

Couplage Spin-mécanique avec des micro-particules en lévitation dans un piège de Paul

Inspired by experiments on cold atoms and ions, the field optomechanics has made major steps towards realizing quantum mechanical experiments with macroscopic mechanical oscillators. Hybrid systems such as the spin of Nitrogen Vacancy (NV) centers coupled to a mechanical oscillator levitating under vacuum offer another promising approach. In this work, we levitate microdiamonds with ensembles of embedded NV spins and explore effects related to the coupling between the NV spins and the libration (angular oscillations) of the micro-diamonds. Levitation is carried out by a Paul trap, which confines both the center of mass and angular degrees of freedom of a charged micro-diamond. In a first set of experiments, we demonstrate angular stability using NV spins and perform spin echoes with levitating diamonds, showing no detectable impact of the trapping mechanism on the NV spin coherence and lifetime. We then use highly doped diamonds with large NV spin ensembles to exert a spin-dependent torque on a levitating micro-diamond. The observation of an NV spin-induced torque on a mechanical oscillator offers many prospects, such as controlling the mechanical oscillator in the quantum regime, spin-spin coupling or room temperature quantum nondestructive read-out, in the single spin limit. Here the most direct application is the use of these ensembles to apply a non-conservative back-action on the angular motion of the diamond. This results in cooling or amplification of the librational modes of the diamond. The main limitation of the current system is the low mechanical frequencies compared to the NV spin decoherence rate. To leverage this issue we levitate both ferromagnetic and composite ferromagnetic-diamond particles. We show one can use the magnetic moment of these particles to gain two order of magnitude in confinement for the angular degree of freedom, putting the mechanical frequencies higher than NV spin decoherence rates in high-purity diamond samples.Inspirée des expériences d’atomes froids ou d’ions piégés, l’opto-mécanique a réalisé d’importants progrès vers des expériences de mécanique quantique avec un oscillateur mécanique macroscopique. Une autre approche prometteuse est l'utilisation de systèmes hybrides ou le couplage entre un atome et un oscillateur mécanique permet le contrôle cohérent de ce dernier. Dans ce travail, les modes de librations (oscillation angulaire) de micro-diamants en lévitation constituent l'oscillateur mécanique. Celui-ci est couplé via un champ magnétique aux spins de centres azote-lacune (NV) contenus dans le micro-diamant. Ce couplage permet alors le refroidissement du mouvement du micro-diamant, similairement au refroidissement Doppler d'ions ou d'atomes piégés. La lévitation est réalisée à l’aide d’un piège de Paul qui confine le centre de masse, mais également les degrés de liberté angulaires d’un micro-diamant chargé. Lors des premières expériences, nous utilisons les centres NV pour démontrer la stabilité angulaire et montrons que leurs propriétés de spin (cohérence, temps de vie) ne sont pas affectées par le piège. Nous faisons ensuite léviter des diamants hautement dopés contenant un grand nombre de centres NV et utilisons leur spin pour exercer un couple sur le micro-diamant en lévitation. L’observation de ce couple ouvre de nombreuses perspectives telles que le contrôle de l’oscillateur mécanique dans le régime quantique, le couplage spin-spin et dans la limite du spin unique, la mesure non-destructive d’un spin NV à température ambiante. Ici l’application la plus directe de cet effet est l’utilisation de ces ensembles de spins pour exercer une rétroaction non-conservative sur le mouvement angulaire du diamant. Cela résulte en un refroidissement ou une amplification du mode de libration du diamant. La principale limitation de ce système est la faiblesse des fréquences de l’oscillateur mécanique comparées au taux de décohérence des spins des centres NV. Pour résoudre ce problème, nous utilisons des particules ferromagnétiques ainsi que des particules composites ferromagnétique-diamant en lévitation. Nous montrons que le moment magnétique de ces particules peut être utilisé pour augmenter le confinement angulaire de deux ordres de grandeur, plaçant ainsi les fréquences de l’oscillateur mécanique au-delà des taux de décohérences typiques de centres NV dans des diamants ultra-pures

Continuous regime quantum teleportation experiment for hybrid quantum nodes

International audienceWe report a telecom teleportation experiment involving narrowband entangled photons and faint laser pulses. This opens the route towards hybrid quantum nodes combining cold-atom single photon sources and entanglement-based quantum relays