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Point defects in diamond known as nitrogen-vacancy centres have been shown to be sensitive to minute magnetic fields, even at room temperature. A demonstration that the spin associated with these defect centres is also sensitive to electric fields holds out the prospect of a sensor that can resolve, under ambient conditions, single spins and single elementary charges at the nanoscale. The ability to sensitively detect individual charges under ambient conditions would benefit a wide range of applications across disciplines. However, most current techniques are limited to low-temperature methods such as single-electron transistors 1 , 2 , single-electron electrostatic force microscopy 3 and scanning tunnelling microscopy 4 . Here we introduce a quantum-metrology technique demonstrating precision three-dimensional electric-field measurement using a single nitrogen-vacancy defect centre spin in diamond. An a.c. electric-field sensitivity reaching 202±6 V cm −1  Hz −1/2 has been achieved. This corresponds to the electric field produced by a single elementary charge located at a distance of ∼150 nm from our spin sensor with averaging for one second. The analysis of the electronic structure of the defect centre reveals how an applied magnetic field influences the electric-field-sensing properties. We also demonstrate that diamond-defect-centre spins can be switched between electric- and magnetic-field sensing modes and identify suitable parameter ranges for both detector schemes. By combining magnetic- and electric-field sensitivity, nanoscale detection and ambient operation, our study should open up new frontiers in imaging and sensing applications ranging from materials science to bioimaging.

Consolidation of ultrafast optics in electron spectroscopies based on free electron energy exchange with matter has matured significantly over the past two decades, offering an attractive toolbox for the exploration of elementary events with unprecedented spatial and temporal resolution. Here, we propose a technique for monitoring electronic and nuclear molecular dynamics that is based on self-heterodyne coherent beating of a broadband pulse rather than incoherent population transport by a narrowband pulse. This exploits the strong exchange of coherence between the free electron and the sample. An optical pulse initiates matter dynamics, which is followed by inelastic scattering of a delayed high-energy broadband single-electron beam. The interacting and noninteracting beams then interfere to produce a heterodyne-detected signal, which reveals snapshots of the sample charge density by scanning a variable delay T. The spectral interference of the electron probe introduces high-contrast phase information, which makes it possible to record the electronic coherence in the sample. Quantum dynamical simulations of the ultrafast nonradiative conical intersection passage in uracil reveal a strong electronic beating signal imprinted onto the zero-loss peak of the electronic probe in a background-free manner.

We propose a method to study the thermodynamic behaviour of small systems beyond the weak coupling and Markovian approximation, which is different in spirit from conventional approaches. The idea is to redefine the system and environment such that the effective, redefined system is again coupled weakly to Markovian residual baths and thus, allows to derive a consistent thermodynamic framework for this new system-environment partition. To achieve this goal we make use of the reaction coordinate (RC) mapping, which is a general method in the sense that it can be applied to an arbitrary (quantum or classical and even time-dependent) system coupled linearly to an arbitrary number of harmonic oscillator reservoirs. The core of the method relies on an appropriate identification of a part of the environment (the RC), which is subsequently included as a part of the system. We demonstrate the power of this concept by showing that non-Markovian effects can significantly enhance the steady state efficiency of a three-level-maser heat engine, even in the regime of weak system-bath coupling. Furthermore, we show for a single electron transistor coupled to vibrations that our method allows one to justify master equations derived in a polaron transformed reference frame.

Motivated by recent progress in electron quantum optics, we revisit the question of single-electron entanglement, specifically whether the state of a single electron in a superposition of two separate spatial modes should be considered entangled. We first discuss a gedanken experiment with single-electron sources and detectors, and demonstrate deterministic (i. e. without post-selection) Bell inequality violation. This implies that the single-electron state is indeed entangled and, furthermore, nonlocal. We then present an experimental scheme where single-electron entanglement can be observed via measurements of the average currents and zero-frequency current cross-correlators in an electronic Hanbury Brown-Twiss interferometer driven by Lorentzian voltage pulses. We show that single-electron entanglement is detectable under realistic operating conditions. Our work settles the question of single-electron entanglement and opens promising perspectives for future experiments.

We theoretically investigate the propagation of heat currents in a three-terminal quantum dot engine. Electron-electron interactions introduce state-dependent processes which can be resolved by energy-dependent tunneling rates. We identify the relevant transitions which define the operation of the system as a thermal transistor or a thermal diode. In the former case, thermal-induced charge fluctuations in the gate dot modify the thermal currents in the conductor with suppressed heat injection, resulting in huge amplification factors and the possible gating with arbitrarily low energy cost. In the latter case, enhanced correlations of the state-selective tunneling transitions redistribute heat flows giving high rectification coefficients and the unexpected cooling of one conductor terminal by heating the other one. We propose quantum dot arrays as a possible way to achieve the extreme tunneling asymmetries required for the different operations.

Poly(2-methoxyethyl acrylate) (PMEA) and poly(ethylene oxide) (PEO) have protein-antifouling properties and blood compatibility. ABA triblock copolymers (PMEAl-PEO11340-PMEAm (MEOMn; n is average value of l and m)) were prepared using single-electron transfer-living radical polymerization (SET-LRP) using a bifunctional PEO macroinitiator. Two types of MEOMn composed of PMEA blocks with degrees of polymerization (DP = n) of 85 and 777 were prepared using the same PEO macroinitiator. MEOMn formed flower micelles with a hydrophobic PMEA (A) core and hydrophilic PEO (B) loop shells in diluted water with a similar appearance to petals. The hydrodynamic radii of MEOM85 and MEOM777 were 151 and 108 nm, respectively. The PMEA block with a large DP formed a tightly packed core. The aggregation number (Nagg) of the PMEA block in a single flower micelle for MEOM85 and MEOM777 was 156 and 164, respectively, which were estimated using a light scattering technique. The critical micelle concentrations (CMCs) for MEOM85 and MEOM777 were 0.01 and 0.002 g/L, respectively, as determined by the light scattering intensity and fluorescence probe techniques. The size, Nagg, and CMC for MEOM85 and MEOM777 were almost the same independent of hydrophobic DP of the PMEA block.

The sensitivities of light Dark matter particle searches with cryogenic detectors are mostly limited by large backgrounds of events that do not produce ionization signal. The CRYOSEL project develops a new technique, where this background in a germanium cryogenic detector is rejected by using the signals from a superconducting single electron device (SSED) sensor designed to detect the phonons emitted through the Neganov–Trofimov–Luke effect by the e - h + pairs as they drift in a nearby very high-field region. A tag on signals from this device should suppress the heat-only background. The measurement of the response to IR laser pulses of the first CRYOSEL prototype show the relevance of such sensor technology.

The TIO 2 -H 2 O 2 system possesses excellent oxidation activity even under dark conditions. However, the mechanism of this process is unclear and inconsistent. In this work, the binary component system containing TiO 2 nanoparticles (NPs) with single electron-trapped oxygen vacancy (SETOV, Vo) and H 2 O 2 exhibit excellent oxidative performance for tetracycline, RhB, and MO even without light irradiation. We systematically investigated the mechanism for the high activity of the TIO 2 -H 2 O 2 under dark condition. Reactive oxygen species (ROS) induced from H 2 O 2 play a significant role in improving the catalytic degradation activities. X-ray photoelectron spectroscopy (XPS) and electron paramagnetic resonance (EPR) results firstly confirm that H 2 O 2 is primarily activated by SETOVs derived from the TiO 2 NPs through direct contribution of electrons, producing both 02-/·AOOH and ·OH, which are responsible for the excellent reactivity of TiO 2 -H 2 O 2 system. This work not only provides a new perspective on the role of SETOVs playing in the H 2 O 2 activation process, but also expands the application of TiO 2 in environmental conservation.

Catalyst innovation lies at the heart of transition-metal-catalyzed reaction development. In this article, we have explored the C(sp 2 )—H alkenylation activity with novel spirocyclic N-heterocyclic carbene (NHC)-based cyclometalated ruthenium pincer catalyst system, SNRu-X . After screening catalyst and condition, a high valent Ru(IV) dioxide (X = O 2 ) species has demonstrated superior reactivity in the catalytic alkenylation of aromatic and olefinic C-H bonds with unactivated alkenyl bromides and triflates. This reaction has achieved the easy construction of a wide range of (hetero)aromatic alkenes and dienes, in good to excellent yields with exclusive selectivity. Preliminary mechanistic studies indicate that this reaction may proceed through a single electron transfer (SET) triggered oxidative addition, by doing so, providing valuable complementary to classical alke-nylation reactions that are dependent on activated alkenyl precursors.

Hybrid turnstiles have proven to generate accurate single-electron currents. The usual operation consists of applying a periodic modulation to a capacitively coupled gate electrode and requires a nonzero DC source-drain bias voltage. Under this operation, a current of the same magnitude and opposite direction can be generated by flipping the polarity of the bias. Here, we demonstrate that accurate single-electron currents can be generated under zero average bias voltage. We achieve this by applying an extra periodic modulation with twice the frequency of the gate signal and zero DC level to the source electrode. This creates a time interval, which is otherwise zero, between the crossings of tunnelling thresholds that enable single-electron tunnelling. Furthermore, we show that within this operation the current direction can be reversed by only shifting the phase of the source signal.