Our research focuses on development of new methods for creating and probing matterwave interferometers.
Paper: Detection of multiple forces at same time with a BEC interferometer
Our latest paper uses a symmetric matterwave interferometer, with an 87Rb BEC, to measure the background level of magnetic and gravitational forces simultaneously. A key result is that we have devised a method of measuring the ambient forces that are always present in the lab, even though these are too small to be detected in normal operation. The trick we use is to apply a number of known magnetic-field gradients to the system and to use precise data fitting to infer the background forces.
Detection of Applied and Ambient Forces with a Matterwave Magnetic-Gradiometer
Phys. Rev. A 96, 053622 (2017).
Prize for Andrew MacKellar
Andrew MacKellar won first prize at the SUPA Student Poster Competition 2016 for his poster on “Phase-contrast interferometry: Single-shot, phase insensitive readout of an atom interferometer”. Further details of this prestigious award can be found at the SUPA website by following this link.
Inductive ring trap
We want to build an atom interferometer for inertial sensing based on our proposal for an inductively coupled ring trap for cold atoms. Our goal is to build a dual species Sagnac interferometer suitable for precision rotation measurements. Such a device has important applications in the field of inertial navigation, where the ability to accurately track position without use of GPS requires a higher sensitivity than is possible with state-of-the-art optical interferometers. Initially, ring experiments are being performed with bosonic 87Rb, however we will investigate the enhanced (interaction-free) interferometry afforded by fermionic species (40K).
A copper ring is placed at the centre of the uniform AC magnetic field generated by a pair of Helmholtz coils (green), which inductively couples an opposing current in the copper ring to create a cylindrically symmetric, inhomogeneous magnetic field. Time-averaging of the combined fields results in a ring trap potential suitable for trapping laser cooled atoms. As there are no wires connecting to a power supply, the ring will have no end effects, and should benefit from increased smoothness due to the AC nature of the magnetic field. Combined with a pair of DC bias coils (grey) to control the position of the magnetic field zeros, this creates an ideal trap for performing precision rotation measurements using Sagnac interferometry. The trap geometry, and hence enclosed area, is also scalable by changing the size of the copper ring that defines the trap radius.
As a first step towards the interferometer the inductive ring trap concept has been demonstrated using a copper ring with internal and external radii of 7 mm and 12 mm respectively. The ring is driven with an AC field amplitude of 110 G oscillating at 30 kHz, inducing a peak current of 140 A inside the copper ring, resulting in a time-averaged ring trap of radius 5.1 mm. The figure shows experiment data obtained from loading a laser cooled ensemble of 87Rb atoms into the ring trap after 200 ms using a 4.6 G axial DC bias field. Characterisation of the trapping potential shows that it is possible to obtain a vacuum-limited lifetime within the ring trap, making it suitable for atom interferometry with long interaction times. Full details can be found in our paper arXiv:1207.4225.
On 2013-02-13 the first BEC in our new vacuum chamber was seen. We use a hybrid trap system, with a crossed optical dipole trap and can now create BECs of 105 atoms.
Dr Andrew MacKellar – now at Durham University.
Dr Billy Robertson – now at NPL.
Dr Jonathan Pritchard – now leader of Hybrid Quantum Technologies group.
Dr Aline Dinkelaker – now at Humboldt-Universität, Berlin
Anna Gribbon –
Mathieu de la Motte Saint Pierre – intern from UPMC, Paris
Niamh Keegan – now at Durham University JQC
- B. I. Robertson, A. R. MacKellar, J. Halket, A. Gribbon, J. D. Pritchard, A. S. Arnold, E. Riis, and P. F. Griffin, Detection of Applied and Ambient Forces with a Matterwave Magnetic-Gradiometer, Phys. Rev. A 96, 053622 (2017).
- G.A. Sinuco-León, K.A. Burrows, A.S. Arnold & B.M. Garraway, Inductively guided circuits for ultracold dressed atoms, Nature Comm. 5, 5289 (2014).
- Vangeleyn, M; Garraway, BM; Perrin, H; Arnold, AS, Inductive dressed ring traps for ultracold atoms, J. Phys. B 47, 071001 (2014).
- J.D. Pritchard, A.N. Dinkelaker, A.S. Arnold, P.F. Griffin and E. Riis, Demonstration of an inductively coupled ring trap for cold atoms, New J. Phys. 14, 103047 (2012).
- P.F. Griffin, E. Riis and A. S. Arnold, Smooth inductively coupled ring trap for atoms, Phys. Rev. A 77, 051402(R) (2008).
- A.S. Arnold, Adaptable-radius, time-orbiting magnetic ring trap for Bose-Einstein condensates, J. Phys. B 37, L29 (2004).