The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems, as established by test beam measurements and simulation studies, is described.

We report on a stepwise on-surface polymerization reaction leading to oriented graphene nanoribbons on Au(111) as the final product. Starting from the precursor 4,4″-dibromo-p-terphenyl and using the Ullmann coupling reaction followed by dehydrogenation and C-C coupling, we have developed a fine-tuned, annealing-triggered on-surface polymerization that allows us to obtain an oriented nanomesh of graphene nanoribbons via two well-defined intermediate products, namely, p-phenylene oligomers with reduced length dispersion and ordered submicrometric molecular wires of poly(p-phenylene). A fine balance involving gold catalytic activity in the Ullmann coupling, appropriate on-surface molecular mobility, and favorable topochemical conditions provided by the used precursor leads to a high degree of long-range order that characterizes each step of the synthesis and is rarely observed for surface organic frameworks obtained via Ullmann coupling.

Observing and controlling macroscopic quantum systems has long been a driving force in research on quantum physics. In this endeavor, strong coupling between individual quantum systems and mechanical oscillators is being actively pursued [1][2][3]. While both read-out of mechanical motion using coherent control of spin systems [4][5][6][7][8][9] and single spin read-out using pristine oscillators have been demonstrated [10, 11], temperature control of the motion of a macroscopic object using long-lived electronic spins has not been reported. Here, we observe both spin-dependent torque and dynamical back-action using a trapped micro-diamond. Using a combination of microwave and laser excitation enables the spin of nitrogen-vacancy centers to act on the diamond orientation and to cool the diamond libration. Further, driving the system in the non-linear regime, we demonstrate bistability and self-sustained coherent oscillations stimulated by the spin-mechanical coupling, which offers prospects for spin-driven generation of non-classical states of motion. Such a levitating diamond operated as a compass with controlled dissipation has implications in high-precision torque sensing [12][13][14], emulation of the spin-boson problem [15] and probing of quantum phase transitions [16]. In the single spin limit [17] and employing ultra-pure nano-diamonds [18], it will allow quantum nondemolition read-out of the spin of nitrogen-vacancy centers under ambient conditions, deterministic entanglement between distant individual spins [19] and matter-wave interferometry [16, 20,21].

The tunable properties of molecular materials place them among the favorites for a variety of future generation devices. In addition, to maintain the current trend of miniaturization of those devices, a departure from the present top-down production methods may soon be required and self-assembly appears among the most promising alternatives. On-surface synthesis unites the promises of molecular materials and of self-assembly, with the sturdiness of covalently bonded structures: an ideal scenario for future applications. Following this idea, we report the synthesis of functional extended nanowires by self-assembly. In particular, the products correspond to one-dimensional organic semiconductors. The uniaxial alignment provided by our substrate templates allows us to access with exquisite detail their electronic properties, including the full valence band dispersion, by combining local probes with spatial averaging techniques. We show how, by selectively doping the molecular precursors, the product’s energy level alignment can be tuned without compromising the charge carrier’s mobility.

We report observations of the electron spin resonance (ESR) of nitrogen vacancy centers in diamonds that are levitating in an ion trap. Using a needle Paul trap operating under ambient conditions, we demonstrate efficient microwave driving of the electronic spin and show that the spin properties of deposited diamond particles measured by the ESR are retained in the Paul trap. We also exploit the ESR signal to show angle stability of single trapped mono-crystals, a necessary step towards spincontrolled levitating macroscopic objects.The negatively charged nitrogen vacancy (NV − ) center in diamond has emerged as a very efficient source of single photons and a promising candidate for quantum control and sensing via its electron spin. Recently, there has been much interest in the electronic spin of the NV − center in levitating diamonds [1,2]. This interest is partly motivated by proposals for hybrid optomechanics [3], and implications in ultrahigh force sensitivity [4] where the NV center's spin response to magnetic fields is exploited to read-out the motion of the diamond with high spatial resolution under ambient conditions [5]. Amongst the many levitation schemes, optical traps are the most widely used [1,[6][7][8]. They provide efficient localization for neutral and charged particles and can work under liquid or atmospheric environnements. However the trap light that is scattered from the object means that excessive heating can be at work [6,7,9,10]. Furthermore, optical traps may quench the fluorescence of NV centers [7] and affect the electronic spin resonance contrast.Being able to trap diamonds hosting NV centers without light scattering could thus offer a better control of the spin-mechanical coupling and enlarge the range of applications of levitating diamonds. Levitation techniques such as ion traps [11] or magneto-gravitational traps [12] are tantalizing approaches for reaching this goal. Ion traps could not only provide an escape route for scattering free trapping, but also enable a high localization of the particles together with large trap depths as demonstrated by the impressive control over the motion that have been developped with single ions in the past [13]. Various nano-objects have been confined in ion traps already, from coloidal nanocrystals [14], silica nanospheres [15,16], graphene flakes [17], micron size diamond clusters containing NV centers [18], showing their potential for the motional control of macroscopic objects.In this work, we report measurements of the electronic spin resonance of NV centers embedded in diamonds that are levitating in an ion trap. Further, we observe high contrast Zeeman-splitted levels, demonstrating angular stability over single levitating monocrystals on time scales of minutes, paving the way towards single spin opto-mechanical schemes in scattering-free traps. The Paul trapAn ion trap typically consists of electrodes that are placed at an oscillating potential generating a time-varying quadrupolar electric field. In the adiabatic regime, this provides a pon...

The surface-assisted synthesis of gold-organometallic hybrids on the Au(111) surface both by thermo- and light-initiated dehalogenation of bromo-substituted tetracene is reported. Combined X-ray photoemission (XPS) and scanning tunneling microscopy (STM) data reveal a significant increase of the surface order when mild reaction conditions are combined with 405 nm light irradiation.

A scheme for strong coupling between a single atomic spin and the rotational mode of levitating nanoparticles is proposed. The idea is based on spin read-out of NV centers embedded in aspherical nanodiamonds levitating in an ion trap. We show that the asymmetry of the diamond induces a rotational confinement in the ion trap. Using a weak homogeneous magnetic field and a strong microwave driving we then demonstrate that the spin of the NV center can be strongly coupled to the rotational motion of the diamond.Experiments in the field of opto-mechanics showed control of macroscopic mechanical oscillators very close to their ground state of motion [1]. These accomplishments provide great opportunities to observe quantum superpositions with macroscopic systems. Although progress are being made with room temperature oscillators [2][3][4], the difficulty in most experiments is that they require cooling of the oscillators down to milliKelvin temperatures or carefully ingineered nano-mechanical oscillators because they are clamped to a structure. Inspired by ideas for mechanical control of oscillating cantilevers using magnetic field sensitive probes [5-9], trapped macroscopic objects coupled to single spins via magnetic field gradients are envisioned [10]. There, the mechanical support is completely removed so one could operate at room temperature and reach high quality factors [11]. Further, the spins coupled to the massive object can be used to create matter wave interference [12] and Schrödinger cat states where the spin is entangled with the collective oscillator motion [10,13].Many experimental protocols are being explored to couple the center of mass mode of levitating objects to single spins, most of which use diamonds with embedded Nitrogen Vacancy (NV) centers in dipole traps [10]. In recent experiments however, despite the mechanical support being completely removed, light scattering from the optically levitated object significantly alters the photophysical properties of the NV centers [14][15][16]. Although advances have been made in this direction [17], many groups indeed observe strong heating at low vacuum pressures which quenches the NV photoluminescence [14,18,19]. On the other hand, scattering free traps such as Paul traps or magneto-gravitational traps allow reaching lower vacuum [20,21] although currently with a lower trapping frequency. One further difficulty with the hybrid proposals is that reaching strong coupling between a single spin and the center of mass mode implies high magnetic field gradients in the range of 10 5 to 10 7 T/m [6,13], which is very challenging.In this paper, we present a scheme for strong coupling between a single spin and levitating nanoparticles that leverages most of these issues. First, we propose using a Paul trap for rotational confinement of charged aspherical nanodiamonds. Second, the rotational degree of freedom is coupled to the spin of embedded NV centers via homogeneous magnetic fields. The proposal makes use of the inherent quantization axis of the NV center toge...

We present measurements of the Electronic Spin Resonance (ESR) of Nitrogen Vacancy (NV) centers in diamonds that are levitating in a ring Paul trap under vacuum. We observe ESR spectra of NV centers embedded in micron-sized diamonds at vacuum pressures of 2 × 10 −1 mbar and the NV photoluminescence down to 10 −2 mbars. Further, we use the ESR to measure the temperature of the levitating diamonds and show that the green laser induces heating of the diamond at these pressures. We finally discuss the steps required to control the NV spin under ultra-high vacuum.Engineering the motional state of massive oscillators will be an important step forward for modern quantum science [1]. Hybrid-opto-mechanical schemes, where the center of mass of oscillators is coupled to single atoms [2], have been propounded to harness this challenge and levitating nano-objects proposed as a viable experimental platform [3,4]. It is indeed possible to benefit from the inherent decoupling of levitating particles internal degrees of freedom from the surrounding environnement and to cool its center of mass mode close to the motional ground state [3,4]. Using hybrid-opto-mechanical schemes with single atoms coupled to or embedded in levitating particles would not only also enable ground state cooling, but also preparing macroscopic non-gaussian motional states and Schrödinger cat states [4] or to perform matter wave interferometry [5][6][7]. To this end, it is important to operate under low vacuum to minimize collisions with air particles, which prevent the center of mass from reaching low temperatures. Thus far, experiments using NV centers embedded in optically levitating diamonds show heating induced by the trapping laser [8][9][10], so that high purity diamonds [11] or higher trapping laser wavelengths [10] need to be used to mitigate this effect. In optical traps, electronic spin read-out of NV centers was observed at tens of millibars of pressure [10], beyond which diamonds are lost from the trap.A solution to particle heating is to use scattering-free traps such as Paul traps [12][13][14][15] or magneto-gravitational traps [16]. In [9,17], the photoluminescence of NV centers in a Paul trap was observed under ambient conditions and the angle stability of the particle was demonstrated using Electronic Spin Resonance (ESR) in [17]. In this paper, we report measurements of the electronic spin resonance of NV centers embedded in diamonds that are levitating in an ion trap under vacuum. Using a slightly modified set-up compared to [17], featuring a small copper ring employed both for trapping and microwave excitation, we could observe the photoluminescence of NV centers at pressures close to 10 −2 mbars for more than 40 minutes. We also detect ESR signals down to 2 × 10 −1 mbars and use it to infer the temperature of the levitating diamond. DM Spectrometer Green laser APD FM g Vacuum gauge P u m p Valve Bias Tee MW HV Objective PD a)