We investigate repeated Bose-Einstein-condensate (BEC) formation and extraction in a dimple trap embedded in a reservoir of thermal atoms using a kinetic model. The model includes pulsed extraction, evaporation, three-body losses, and thermal-atom replenishment. Three extraction protocols are compared: extraction of all atoms from the dimple (BEC and thermal atoms), full and partial extractions of the BEC, but not of the thermal atoms. Residual atoms in the dimple after extraction seed subsequent Bose-stimulated growth and reduce the recovery time between extractions, but also enhance density-dependent losses. For all protocols, repeated extraction of BECs can be achieved without replenishment, but the number of BEC formations is limited by reservoir depletion and heating. With continuous replenishment, the system can reach a periodic steady-state regime, after an initial transient period, controlled by the externally imposed rates of extraction pulses and thermal-atom input. Within the explored parameter range, partial BEC extraction gives the highest efficiency, particularly for short extraction periods and high input rates. These results identify seeding by residual populations of BECs and thermal atoms as a kinetic mechanism for improving repeated condensate production in dimple traps.

We study Josephson dynamics in a long atomic Bose-Josephson junction formed by two tunnel-coupled coplanar Bose-Einstein-condensate rings. An in-plane linear acceleration breaks the axial symmetry of the trap and transforms a single Josephson plasma oscillation into a multimode population-imbalance response. Gross-Pitaevskii simulations and Bogoliubov-de Gennes analysis show that the additional spectral components arise from collective modes that acquire finite overlap with the population-imbalance operator under symmetry breaking, with their activation governed by reflection symmetry about the acceleration direction. We also propose a mode-resolved Josephson-spectroscopy protocol based on a weak localized periodic perturbation. Frequency scans reveal resonant amplitude peaks and phase shifts at the eigenfrequencies of active Bogoliubov modes, while angular scans of the drive position provide access to the angular structure of the corresponding mode density perturbations. A dissipative time-dependent Bogoliubov theory yields analytical response functions in quantitative agreement with full Gross-Pitaevskii simulations in the linear regime. Our results demonstrate that accelerated dual-ring condensates provide a controllable platform for symmetry-selected Josephson dynamics and spectroscopic probing of collective modes.

Persistent currents–inviscid quantized flow around an atomic circuit–are a crucial building block of atomtronic devices. We investigate how acceleration influences the transfer of persistent currents between two density-connected, ring-shaped atomic Bose-Einstein condensates, joined by a tunable weak link that controls system topology. We find that the acceleration of this system modifies both the density and phase dynamics between the rings, leading to a bias in the periodic vortex oscillations studied in T. Bland et al., Phys. Rev. Research 4, 043171 (2022). Accounting for dissipation suppressing such vortex oscillations, the acceleration facilitates a unilateral vortex transfer to the leading ring. We analyze how this transfer depends on the weak-link amplitude, the initial persistent current configuration, and the acceleration strength and direction. Characterization of the sensitivity to these parameters paves the way for a new platform for acceleration measurements, for which we outline a proof-of-concept ultracold double-ring accelerometer.

We present a proof-of-concept design for an atomtronic rotation sensor consisting of an array of “double-target” Bose-Einstein condensates (BECs). A “target” BEC is a disk-shaped condensate surrounded by a concentric ring-shaped condensate. A “double-target” BEC is two adjacent target BECs whose ring condensates partially overlap. The sensor consists of an n× m array of these double-target BECs. The measurement of the frame rotation speed, Ω_R, is carried out by creating the array of double-target BECs (setup step), inducing one unit of quantized flow in the top ring of each member of the array (initialization step), applying potential barriers in the overlap region of each member (measurement step), and observing whether the induced flow is transferred from the top to the bottom ring in each member (readout step). We describe a set of simulations showing that a single instance of a double-target BEC behaves in a way that enables the efficient operation of an n× m array for measuring Ω_R. As an example of sensor operation we present a simulation showing that a 2×2 array can be designed to measure Ω_R in a user-specified range.

Recent atom interferometry (AI) experiments involving Bose–Einstein condensates (BECs) have been conducted under extreme conditions of volume and interrogation time. Numerical solution of the rotating-frame Gross–Pitaevskii equation (RFGPE), which is the standard mean-field theory applied to these experiments, is impractical due to the excessive computation time and memory required. We present a variational model that provides approximate solutions of the RFGPE for a power-law potential on a practical time scale. This model is well-suited to the design and analysis of AI experiments involving BECs that are split and later recombined to form an interference pattern. We derive the equations of motion of the variational parameters for this model and illustrate how the model can be applied to the sequence of steps in a recent AI experiment where BECs were used to implement a dual-Sagnac atom interferometer rotation sensor. We use this model to investigate the impact of finite-size and interaction effects on the single-Sagnac-interferometer phase shift.

Vorticity in closed quantum fluid circuits is known to arise in the form of persistent currents. In this work, we develop a method to engineer transport of the quantized vorticity between density-coupled ring-shaped atomic Bose-Einstein condensates in experimentally accessible regimes. Introducing a tunable weak link between the rings, we observe and characterize the controllable periodic transfer of the current and investigate the role of temperature on suppressing these oscillations via a range of complementary state-of-the-art numerical methods. Our setup paves the way for precision measurements of local acceleration and rotation.

Atomtronics deals with matter-wave circuits of ultra-cold atoms manipulated through magnetic or laser-generated guides with different shapes and intensities. In this way, new types of quantum networks can be constructed, in which coherent fluids are controlled with the know-how developed in the atomic and molecular physics community. In particular, quantum devices with enhanced precision, control and flexibility of their operating conditions can be accessed. Concomitantly, new quantum simulators and emulators harnessing on the coherent current flows can also be developed. Here, we survey the landscape of atomtronics-enabled quantum technology and draw a roadmap for the field in the near future. We review some of the latest progresses achieved in matter-wave circuits design and atom-chips. Atomtronic networks are deployed as promising platforms for probing many-body physics with a new angle and a new twist. The latter can be done both at the level of equilibrium and non-equilibrium situations. Numerous relevant problems in mesoscopic physics, like persistent currents and quantum transport in circuits of fermionic or bosonic atoms, are studied through a new lens. We summarize some of the atomtronics quantum devices and sensors. Finally, we discuss alkali-earth and Rydberg atoms as potential platforms for the realization of atomtronic circuits with special features.

We investigate the thermal instability of a Bose-Einstein condensate stirred by a rotating barrier in a ring-shaped trap. One would expect the critical angular speed to decrease with increasing temperature due to depletion of the condensate. However, we show that the critical velocity remains approximately constant within a considerable range of temperatures, contrary to expectation, and the thermal cloud has a stabilizing effect.

We present a study of how macroscopic flow can be produced in Bose-Einstein condensates confined in a ``racetrack'' potential by stirring with a wide rectangular barrier. This potential consists of two half-circle channels separated by straight channels of length $L$ and reduces to a ring potential if $L=0$. We present the results of a flow-production study where racetrack condensates were stirred with a barrier under varying conditions of barrier height, stir speed, racetrack geometry, and temperature. The result was that stirring was readily able to produce flow in ring and nonring geometries but that the exact amount of flow produced depended on all of the study parameters. We therefore investigated the mechanism by which flow was produced in the stirring process. The basic mechanism that we discovered was that when the sweeping barrier potential height reached a critical value a series of phase slip (i.e., a sudden change in the phase winding around the condensate midtrack) events occurred. Phase slipping stopped when the flow produced overtook the speed of the stirring barrier. Disturbances generated at each phase slip circulated around the channel and served to convert the initially localized velocity distribution into smooth macroscopic flow. This picture of the mechanism for making flow should facilitate the design of closed-channel atom circuits for creating a desired amount of quantized smooth flow on demand.

We have studied the efficacy of stirring a Bose–Einstein condensate confined in a racetrack atom circuit to produce neutral–atom flow. We also investigated the mechanism by which flow is produced.

Atomtronics is an emerging field of quantum technology dealing with matter-wave circuits of ultra-cold atoms manipulated in magnetic or laser-generated guides of different shapes and intensity. Atomtronic circuits are promised to define quantum networks of new types in which coherent fluids can be feasibly controlled with the know how of the atomic and molecular physics quantum technology. This way, atomtronics can provide the basis for new quantum devices with enhanced precision, control and flexibility. At the same time, new quantum simulators and emulators harnessing coherent current flows can be defined. Here, we survey the atomtronics-enabled quantum technology and we draw a roadmap on the field for the years to come. The latest progress achieved in matter-wave circuits design and atom-chips are reviewed. Atomtronic networks have been used as platforms to study many-body physics in a new way, both at equilibrium and at non-equilibrium. Relevant problems in mesoscopic physics, like persistent currents and quantum transport in circuits of fermionic or bosonic atoms, have been studied with a new twist. We discuss the state of the art and the perspectives for the quantum devices and sensors implied by coherent matter-wave physics principles. Finally, we discuss alkali-earth and Rydberg atoms as great potential platforms for the realization of atomtronic circuits of a new type.

We systematically construct stationary soliton states in a one-component, two-dimensional, repulsive, Gross-Pitaevskii equation with a ring-shaped target-like trap similar to the potential used to confine a Bose-Einstein condensate in a recent experiment [Eckel, et al.\ {\em Nature} {\bf 506}, 200 (2014)]. In addition to the ground state configuration, we identify a wide variety of excited states involving phase jumps (and associated dark solitons) inside the ring. These configurations are obtained from a systematic bifurcation analysis starting from the linear, small atom density, limit. We study the stability, and when unstable, the dynamics of the most basic configurations. Often these lead to vortical dynamics inside the ring persisting over long time scales in our numerical experiments. To illustrate the relevance of the identified states, we showcase how such dark-soliton configurations (even the unstable ones) can be created in laboratory condensates by using phase-imprinting techniques.

We present a variational model suitable for rapid preliminary design of atom interferometers in a microgravity environment. The model approximates the solution of the three-dimensional rotating-frame Gross-Pitaevskii equation as the sum of N-c Gaussian clouds. Each Gaussian cloud is assumed to have time-dependent center positions, widths, and linear and quadratic phase parameters. We applied the Lagrangian variational method (LVM) with this trial wave function to derive equations of motion for these parameters that can be adapted to any external potential. We also present a one-dimensional (1D) version of this variational model. As an example we apply the model to a 1D atom interferometry scheme for measuring Newton's gravitational constant, G, in a microgravity environment. We show how the LVM model can (1) constrain the experimental parameter space size, (2) show how the value of G can be obtained from the experimental conditions and interference pattern characteristics, and (3) show how to improve the sensitivity of the measurement and construct a preliminary error budget.