Southwest Quantum Information and Technology

A DC-SQUID force sensor: an atomtronic proposal

Presenting Author: Eddy Timmermans, (Los Alamos)
Contributing Author(s): Malcolm Boshier

In atomtronics cold atom physicists laser-guide ultra-cold atoms in closed flow patterns that resemble the current of an electronic circuit. The control of and measurement on such flows can realize novel sensing protocols. Following a superfluid helium proposal, the recently reported Bose-Einstein condensate (BEC) superfluid quantum interference devices (SQUIDs) can, in principle, measure rotations. The reported BEC-SQUID - a single loop BEC with movable effective potential barriers that act as Josephson constrictions - realized the two arm geometry of interferometers and demonstrated the Josephson constricted critical current of conventional superconducting SQUIDs. However, these atomtronic devices did not support the flow-through current that feeds into and out of the superfluid SQUID loop of direct current (DC) SQUIDs. We propose an atomtronic BEC-SQUID design that is based on a two-loop geometry, in which the two loops share a leg: One loop of finite winding number controls the BEC current that feeds into a second loop of two Josephson constricted arms. We propose to meet the challenge of measuring the current of a neutral, superfluid particle flow by controlling the length of the control loop at fixed winding number. The control loop length at which the steady flow of the SQUID loop ceases to be superfluid is the critical length. We develop the direct current superfluid circuit analysis that predicts the critical length. We show that the effect of a weak external force on the dispersion of the coherent BEC wave can be described by an effective index of refraction. The weak external force alters the critical length and determining the critical length can measure the force on a micron scale distance and possibly at high resolution.

(Session 12 : Saturday from 2:15 pm - 2:45 pm)