arXiv subjects

Wenxi Lai

Publications and source records attributed to Wenxi Lai.

15 recordsLinked to original sources

arXiv2026

A general formula for the amplitude-frequency ratio in shaking induced Mott insulator of atomtronic transistors

Mott insulator of atomic transport can be realized in shaken optical lattices by choosing particular ratio of driving amplitude and frequency, which has been studied as Floquet engineering with time-independent effective Hamiltonian approach. Here, we give a general formula of amplitude-frequency ratio for realization of the shaking induced insulator-conductor transition in a double-well open system, using numerical computation with instantaneous eigenstates approach. The result is owing to the fact that the instantaneous eigenstates approach is applicable in wider parameter range compared with the time-independent effective Hamiltonian approach. Analysis from the results of quantum master equation shows that the insulator effect is originated from coherent localization of atom wave packets in optical wells.

cond-mat.quant-gas↗

arXiv2026

Optical purification of materials based on atom walking in traveling-wave lights

An optical method for precise purification of chemical elements is introduced in this paper. The materials are supposed to be in the states of gaseous beams, which are coherently coupled to an external traveling light during purification. Before decoherence occurs, atoms periodically move in the light with different speeds that depends on masses and optical transition wave lengths of these atoms. The speed gradient leads to deflections of different atoms in different directions. The model is described by Schrödinger equations with analytical results. This method could be used for some hardly separable atoms and isotopes depending on the condition of atom coherent time. The present work opens a platform for applications of cold atom technology in the purification of atoms and molecules.

quant-ph↗

arXiv2026

Atomtronic superconducting quantum interference device in synthetic dimensions

Coherence and scalability are essential properties of quantum systems required in quantum computers. This study presents a high coherent and scalable qubit system with atomtronics in synthetic dimensions. It is atomtronic counterpart of superconducting quantum interference device. Comparing with traditional superconducting quantum interference device which requires at least $2$-dimensional circuits, the synthetic dimensional superconducting quantum interference device can be realized only in $1$-dimensional circuits. The synthetic dimensional system is composed of Bose-Einstein condensate in two neighboring optical wells which is coupled to an external coherent light. Control parameter for the qubit is naturally provided by artificial magnetic flux originated from the coherent atom-light coupling. It should be a great advantage for the scalability and integration feature of quantum logic gates.

cond-mat.quant-gas↗

arXiv2026

A single atom vibration sensor

Previously in vibration sensors, optical glass plates, optical fibres, carbon nanotubes, semiconductor materials, piezoelectric materials and molecules are proved to be effective transducers for sensing vibrations. In this work, for the first time, we will propose a model of vibration sensor using single atom transport in an open optical lattice. In this apparatus, information of mechanical vibration could be transferred into shaking of optical lattice through one of a cavity mirror. Shaking lattice consequently induces Mott insulator due to quantum interference. It is found that information of vibration is encoded in the atomic current and it could be extracted by Fourier transformations. The present atomic vibration sensor has wide detection range of frequency with high precision. Our present model of sensor based on atomic system opens a new area of studying vibration sensors.

cond-mat.quant-gas↗

arXiv2023

Atom walking in a traveling-wave light

In this paper, we investigate mechanical motion of ultra-slow single atoms considering each atom is coherently coupled to a traveling-wave light. The main noise in this system is originated from Doppler broadening due to the continuous momentum distribution in atom wave packet. Here, it is proved that the Doppler broadening could be effectively suppressed in strong coupling regime. Under the coherent coupling, individual neutral atoms periodically walk in a definite direction. Direction of the motion depends on occupation of the atom in its two internal states related to the optical transition, since the atom would be affected by attractive or repulsive forces depending on the internal states. It is analogous to the electric force acting on negatively or positively charged particles. We explain them with spin-orbit coupling of atoms which is hidden in our Hamiltonian. These results have potential applications for the construction of future atomic devices.

quant-ph↗

arXiv2023

Optical Stern-Gerlach effect via a single traveling-wave light

In this paper, we propose a simplified model of optical Stern-Gerlach effect based on coherent coupling between clock transition of alkaline-earth single atoms and a traveling-wave light. It is demonstrated that spin-orbit coupling induced chiral motion in atom deflection appears under the strong atom-light interaction. The strong optical driving removes perturbation from the Doppler effect and back action effect to access the coherent system. In this process, superposition of distant matter waves connected to the arbitrary distribution of atom internal state could be predicted, which is important for the realization of atom interferometry and quantum state operation. The influence from atom relaxation and atom-atom interactions are discussed. Basic conditions of experimental design are given in the end of this work.

quant-ph↗

arXiv2022

Inhomogeneous light photovoltaic effect in neighboring quantum dots

Photovoltaic effect of double quantum dots under nonuniform light field intensity has been studied theoretically. Comparing with the traditional p-n type photovoltaic effect, the inhomogeneous light field provides asymmetric potential creating polarization of electron number distribution in the neighboring quantum dots and furthermore gives rise to net current. Current density and efficiency of such kind solar cells are estimated to be comparable to the traditional p-n type material based solar cells. Motion of electron is described using quantum master equation around room temperature. The inhomogeneous light photovoltaic effect has potential applications for the gain of more economical solar cells.

cond-mat.mes-hall↗

arXiv2021

Photovoltaic transistor of atoms due to spin-orbit coupling in three optical traps

In this paper, spin-orbit coupling induced photovoltaic effect of cold atoms has been studied in a three-trap system which is an two-dimensional extension of a two-trap system reported previously. It is proposed here that atom coherent length is one of the important influence to the resistance of this photovoltaic battery. Current properties of the system for different geometrical structures of the trapping potentials are discussed. Numerical results show extension in the number of traps could cause current increase directly. Quantum master equation at finite temperature is used to treat this opened system. This work may give a theoretical basis for further development of the photovoltaic effect of neutral atoms.

cond-mat.mes-hall↗

arXiv2021

Asymmetric Field Photovoltaic Effect of Neutral Atoms

Photovoltaic effect of neutral atoms using inhomogeneous light in double-trap opened system is studied theoretically. Using asymmetric external driving field to replacing original asymmetric chemical potential of atoms, we create polarization of atom population in the double-trap system. The polarization of atom number distribution induces net current of atoms and works as collected carriers in the cell. The cell can work even under partially coherent light. The whole configuration is described by quantum master equation considering weak tunneling between the system and its reservoirs at finite temperature. The model of neutral atoms could be extended to more general quantum particles in principle.

quant-ph↗

arXiv2020

Spin filter of electrons through a zeeman splitting single quantum dot

Electron spin filter induced by Zeeman splitting in a few-electron quantum dot coupled to two normal electrodes is studied considering Coulomb blockade effect. Based on the Anderson model and Liouville-von Neumann equation, equation of motion of the system is derived and analytical solutions are achieved. Transport windows for perfectly polarized current, partially polarized current and non-polarized current induced by the Zeeman splitting energy and Coulomb blockade potential are exploited. We will give the relations of voltage, magnetic field and temperature for high quality spin filtering.

cond-mat.mes-hall↗

arXiv2019

Photovoltaic Effect of Atomtronics Induced by Artificial Gauge Field

We investigate photovoltaic effect of atomtronics induced by artificial gauge field in four optical potentials. Effective magnetic flux gives rise to polarization of atom occupation probability which creates current of atomtronics. The relation between atomic current and magnetic flux behaves like the current-phase property in Josephson junction. The photovoltaic cell is well defined by the atomic opened system which have effective voltage and two different poles that correspond to two internal states of atomtronics. The atom flow is controllable by changing the direction of incident light and other system parameters. Detection of the atomic current intensity is available through light emission optical spectrum in experiments.

cond-mat.mes-hall↗

arXiv2018

Conduction Bands of Atomic Tunneling Ring in Artificial Gauge Field Assisted Opened Optical Traps

We show conduction bands of artificial gauge field assisted atom flow in triangle optical lattice. The conduction bands are result from periodicity boundary condition of artificial magnetic flux induced phases of atoms. The positions of conduction bands depend on geometry of the atom trajectory. We consider a cell of the triangle optical lattice which is a opened system connected to its environment of Fermion atom clouds. The chemical potentials of the atom clouds are the same and the atom flow is absolutely created by a clock laser induced spin-orbit coupling. Our results are important for the control of atom flow in quantum circuits.

cond-mat.mes-hall↗

arXiv2015

Manipulation of a single magnetic atom using polarized single electron transport in a double quantum dot

We consider theoretically a magnetic impurity spin driven by polarized electrons tunneling through a double quantum dot system. Spin blockade effect and spin conservation in the system make the magnetic impurity sufficiently interact with each transferring electron. As a results, a single collected electron carries information about spin change of the magnetic impurity. The scheme may develop all electrical manipulation of magnetic atoms by means of single electrons, which is significant for the implementation of scalable logical gates in information processing systems.

cond-mat.mes-hall↗

arXiv2013

Dephasing of electrons in the Aharonov-Bohm interferometer with a single-molecular vibrational junction

Phase relaxation of electrons transferring through an electromechanical transistor is studied using the Aharonov-Bohm interferometer. With the approach of quantum master equation, the phase properties of an electron are numerically analyzed based on the interference fringes. Coherence of electron is partially destroyed by its scattering on excited levels of the local nanomechanical oscillator. Transmission amplitudes with respect to two adjacent mechanical vibrational levels have a phase difference of $π$. The character of phase shift by $π$ depends on the oscillator frequency only and is robust for the wide range variance of the applied voltage, tunneling length and damping rate of the mechanical oscillator.

cond-mat.mes-hall↗

arXiv2012

Current-oscillator correlation and Fano factor spectrum of quantum shuttle with finite bias voltage and temperature

A general master equation is derived to describe an electromechanical single-dot transistor in the Coulomb blockade regime. In the equation, Fermi distribution functions in the two leads are taken into account, which allows one to study the system as a function of bias voltage and temperature of the leads. Furthermore, we treat the coherent interaction mechanism between electron tunneling events and the dynamics of excited vibrational modes. Stationary solutions of the equation are numerically calculated. We show current through the oscillating island at low temperature appears step like characteristics as a function of the bias voltage and the steps depend on mean phonon number of the oscillator. At higher temperatures the current steps would disappear and this event is accompanied by the emergence of thermal noise of the charge transfer. When the system is mainly in the ground state, zero frequency Fano factor of current manifests sub-Poissonian noise and when the system is partially driven into its excited states it exhibits super-Poissonian noise. The difference in the current noise would almost be removed for the situation in which the dissipation rate of the oscillator is much larger than the bare tunneling rates of electrons.

cond-mat.mes-hall↗