Related Experiment Video
Updated: Jun 2, 2026
11:21
Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving
Published on: March 30, 2017
Superflow in a toroidal Bose-Einstein condensate: an atom circuit with a tunable weak link
A Ramanathan1, K C Wright, S R Muniz
1Joint Quantum Institute, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
Physical Review Letters
|April 27, 2011
Summary
Researchers created a persistent current in a toroidal Bose-Einstein condensate (BEC). Superflow stopped abruptly when a barrier
Area of Science:
- Quantum physics
- Atomic physics
- Condensed matter physics
Background:
- Bose-Einstein condensates (BECs) are quantum states of matter.
- Creating persistent currents in BECs is crucial for quantum circuit applications.
- All-optical traps offer precise control over BECs.
Purpose of the Study:
- To create and study a persistent current in a toroidal Bose-Einstein condensate.
- To investigate the behavior of superflow through a tunable weak link.
- To determine the critical velocity for dissipation in the condensate circuit.
Main Methods:
- Utilized an all-optical trap to confine a Bose-Einstein condensate in a toroidal shape.
- Introduced a repulsive optical barrier to act as a tunable weak link.
- Measured the persistent current and observed its decay and abrupt cessation.
Main Results:
- Achieved a long-lived persistent current (approximately 40 seconds).
- Observed that superflow abruptly stopped at a critical barrier strength.
- Measured critical velocity consistent with vortex-antivortex pair creation.
Conclusions:
- Demonstrated the first realization of an elementary closed-loop atom circuit.
- The system provides a novel platform for studying quantum dissipation.
- The results have implications for quantum computing and metrology.
Related Concept Videos
01:13Torque On A Current Loop In A Magnetic Field
The most common application of magnetic force on current-carrying wires is in electric motors. These consist of loops of wire, which are placed between the magnets with a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate, thus converting electrical energy to mechanical energy.
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...
Consider a rectangular current-carrying loop containing N turns of wire, placed in a uniform magnetic field. The net force on a current-carrying loop...
01:22Couette Flow
Couette flow represents the flow of fluid between two parallel plates, with one plate fixed and the other moving with a constant velocity. This configuration allows for a simplified analysis using the Navier-Stokes equations, which govern fluid motion under conditions of viscosity and incompressibility. For Couette flow, the assumptions include a steady, laminar, incompressible flow with a zero-pressure gradient in the flow direction. This flow type is beneficial for understanding shear-driven...
01:17Force On A Current Loop In A Magnetic Field
Magnetic forces on wires carrying current are most frequently applied in motors. A DC motor is a device that converts electrical energy into mechanical work. In motors, wire loops are enclosed in a magnetic field. When current flows through the loops, the magnetic field applies torque, which causes the shaft to rotate. The direction of the current is reversed once the loop's surface area is lined up with the magnetic field, causing a constant torque on the loop. During the process, commutators...
01:23Steady, Laminar Flow in Circular Tubes
Hagen-Poiseuille flow describes a viscous fluid's steady, incompressible flow through a cylindrical tube with a constant radius R. This flow profile is often applied to understand fluid transport in narrow channels, such as capillaries. It serves as a foundational example of laminar flow. In this model, cylindrical coordinates (r,θ,z) are used to describe the radial (r), angular (θ), and axial (z) dimensions within the tube. For Hagen-Poiseuille flow, the velocity profile is purely axial,...
01:24Fast Decoupled and DC Powerflow
The fast decoupled power flow method addresses contingencies in power system operations, such as generator outages or transmission line failures. This method provides quick power flow solutions, essential for real-time system adjustments. Fast decoupled power flow algorithms simplify the Jacobian matrix by neglecting certain elements, leading to two sets of decoupled equations:
01:17Steady, Laminar Flow Between Parallel Plates
Understanding steady, laminar flow between parallel plates is essential for analyzing and designing flow in narrow rectangular channels, commonly found in various water conveyance and drainage systems. The Navier-Stokes equations govern fluid motion and are generally challenging to solve due to their nonlinearity. However, simplifications are possible in certain cases, like the steady laminar flow between parallel plates. For this scenario, we assume steady, incompressible, laminar flow.