Building and characterizing a stylus ion-trap system

Cold trapped ions can be excellent sensors for ultra-precision detection of physical quantities,which strongly depends on the measurement situation at hand.The stylus ion trap,formed by two concentric cylinders over a ground plane,holds the promise of relatively simple structure and larger solid angle for optical access and fluorescence collection in comparison with the conventional ion traps.Here we report our fabrication and characterization of the first stylus ion trap constructed in China,aiming for studying quantum optics and sensing weak electric fields in the future.We have observed the stable confinement of the ion in the trapping potential for more than two hours and measured the heating rate of the trap to be dε/dt=7.10±0.13 meV/s by the Doppler recooling method.Our work starts a way to building practical quantum sensors with high efficiency of optical collection and with ultimate goal for contributing to future quantum information technology.

Stochastic Resonance in a Single-Ion Nonlinear Mechanical Oscillator

Stochastic resonance is a counterintuitive phenomenon amplifying the weak periodic signal by application of external noise.We demonstrate the enhancement of a weak periodic signal by stochastic resonance in a trappedion oscillator when the oscillator is excited to the nonlinear regime and subject to an appropriate noise.Under the full control of the radio-frequency drive voltage,this amplification originates from the nonlinearity due to asymmetry of the trapping potential,which can be described by a forced Duffing oscillator model.Our scheme and results provide an interesting possibility to make use of controllable nonlinearity in the trapped ion,and pave the way toward a practical atomic sensor for sensitively detecting weak periodic signals from real noisy environment.

Analytical treatment of Anderson localization in a chain of trapped ions experiencing laser Bessel beams

Trapped ions, under electromagnetic confinement and Coulomb repulsion, can behave as non-interacting particles in one-dimensional lattices. Here we explore analytically the possible effects regarding Anderson localization in a chain of trapped ions experiencing laser Bessel beams. Under an experimentally feasible condition, we predict an analytical form of the energy-dependent mobility edges, which is verified to be in good agreement with the exact numerical results except for the top band. Some other important properties regarding the phonon localization in the ion chain are also discussed both analytically and numerically. Our results are relevant to experimental observation of localization–delocalization transition in the ion trap and helpful for deeper understanding of the rich phenomena due to long-range phonon hopping.

Ground state cooling of an optomechanical resonator with double quantum interference processes

We present a cooling scheme with a tripod configuration atomic ensemble trapped in an optomechanical cavity.With the employment of two different quantum interference processes,our scheme illustrates that it is possible to cool a resonator to its ground state in the strong cavity-atom coupling regime.Moreover,with the assistance of one additional energy level,our scheme takes a larger cooling rate to realize the ground state cooling.In addition,this scheme is a feasible candidate for experimental applications.

N-doped core-shell mesoporous carbon spheres embedded by Ni nanoparticles for CO_(2)electroreduction

Herein,we successfully prepare highly dispersed and uniform small nano-size nickel nanoparticles embedded on core-shell carbon spheres by confined-deposition method.The mesoporous silica layer containing surfactant coated on the surface of the polymer sphere provides confined space and effectively controls the growth of nickel nanoparticles during pyrolysis.At the same time,the introduction of nickel species has an impact on structure of the obtained carbon spheres,and it can promote the deposition of carbon to realize the adjustment from hollow to core-shell and then to solid spheres.Owing to the uniform distribution of Ni nanoparticles with small size,mesoporous structure,N-doping groups,high specified surface areas,and core-shell structure,the obtained catalyst shows exciting ability for the production of CO by reduction of CO_(2)with a maximum CO Faradaic efficiency of 98%,indicating its promising prospect in electro-reduction of CO_(2).

100 cm^(2) Organic Photovoltaic Cells with 23%Efficiency under Indoor Illumination

The application of organic photovoltaic(OPV)cells to drive off-grid microelectronic devices under indoor light has attracted broad attention.As organic semiconductors intrinsically have less ordered intermolecular packing than inorganic materials,the relatively larger energetic disorder is one of the main results that limit the photovoltaic efficiency of the OPV cells at low carrier density.Here,we optimize the alkyl chains of non-fullerene acceptors to get suppressed energetic disorder.We find the optimal acceptor DTz-R1 with the shortest alkyl chain has the strongest crystalline property and lowest energetic disorder.As a result,over 26%efficiency is recorded for the 1 cm^(2) OPV cells under a light-emitting diode illumination of 500 lux.We also fabricate a 100 cm^(2) cell device and get a PCE of 23.0%,which is an outstanding value for large-area OPV cells.These results suggest that modulation of the energetic disorder is of great importance for further improving the efficiency of OPV cells,especially for indoor applications.

Chiral quantum heating and cooling with an optically controlled ion

Quantum heat engines and refrigerators are open quantum systems,whose dynamics can be well understood using a non-Hermitian formalism.A prominent feature of non-Hermiticity is the existence of exceptional points(EPs),which has no counterpart in closed quantum systems.It has been shown in classical systems that dynamical encirclement in the vicinity of an EP,whether the loop includes the EP or not,could lead to chiral mode conversion.Here,we show that this is valid also for quantum systems when dynamical encircling is performed in the vicinity of their Liouvillian EPs(LEPs),which include the effects of quantum jumps and associated noise—an important quantum feature not present in previous works.We demonstrate,using a Paul-trapped ultracold ion,the first chiral quantum heating and refrigeration by dynamically encircling a closed loop in the vicinity of an LEP.We witness the cycling direction to be associated with the chirality and heat release(absorption)of the quantum heat engine(quantum refrigerator).Our experiments have revealed that not only the adiabaticity breakdown but also the Landau–Zener–Stückelberg process play an essential role during dynamic encircling,resulting in chiral thermodynamic cycles.Our observations contribute to further understanding of chiral and topological features in non-Hermitian systems and pave a way to exploring the relation between chirality and quantum thermodynamics.