Jun 27

Continuous dynamical decoupling preprint on the arXiv

Driving transitions between spin states creates new ‘continuous dynamical decoupled’ states, sensitive to oscillating fields yet protected from low-frequency drifts and inhomogeneities. We continuously observe an ultracold spin-1 gas undergoing such decoupling, measuring the populations, splittings, and couplings of the new states in real time [1]. This characterization is completed during a single experimental preparation, rather than the hundreds required with projective measurement. We show that one state-pair is protected to fourth-order with respect to field instabilities, higher than the quadratic suppression of standard decoupling. Combining continuous measurement with continuous decoupling will enable feedback and tracking capabilities for noise-robust atomic magnetometry. This work complements parallel measurements of the same rf-dressed system by Trypogeorgos et al. using projective readout of dressed state populations at higher magnetic fields [2].

[1] R. P. Anderson, M. J. Kewming, L. D. Turner. Continuously observing a dynamically decoupled spin-1 quantum gas. arXiv:1706.08322.
[2] D. Trypogeorgos, A. Valdés-Curiel, N. Lundblad, I. B. Spielman. Synthetic clock transitions via continuous dynamical decoupling. arXiv:1706.07876.

Jan 04

Hologram paper in Optics Express

The Helmerson lab’s work on high efficiency, low cost holographic optical elements for ultracold atom trapping has been published in Optics Express! You can read about how we create static elements to avoid using an SLM directly on our apparatus at https://doi.org/10.1364/OE.25.000296

An example of a Hermite-Gauss hologram, used to provide the tight trapping in one dimension required to form a pancake-shaped BEC.

An example of a Hermite-Gauss hologram, used to provide the tight trapping in one dimension required to form a pancake-shaped BEC.

Jul 27

Vector light shift preprint on the arXiv

The Spinor Lab have released a preprint on measurement and cancellation of vector light shifts in optical dipole traps [1]. The optical dipole force was first used to trap neutral atoms by Chu, et al. 30 years ago [2]. The following decade, and three years after the realisation of Bose-Einstein condensates of dilute gases, optical dipole traps were used to confine BECs [3], heralding the study of spinor BECs. Unlocking the spin degree-of-freedom of the condensate relies on being able to confine multiple spin states simultaneously. When all spin states of a condensate are confined equally, the spin dynamics are largely decoupled from the spatial degree-of-freedom. However, this relies on a precisely linear polarisation state of the trapping light, imperfections of which can result in a spin-dependent energy shift. Such vector light shifts are apparent as a `fictitious’ magnetic field, and the same intensity curvature used to generate the trapping potential is manifest as an effective magnetic field gradient. These gradients are deleterious for preserving coherent spin evolution, and vector light shifts more generally are a hindrance for atomic magnetometry from nanokelvin to room temperatures. A significant part of Alex Wood’s PhD involved characterising and controlling this phenomenon using two spinor BECs in proximity to each other. This result also constitutes our first magnetically sensitive trapped-atom interferometer, with an interrogation time of 15 milliseconds.

Update (23/09/2016): This paper has been accepted by Physical Review A. Based on peer review, we added an appendix on thermally induced birefringence by the dipole trapping beams on glass vacuum windows.

[1] A. A. Wood, L. D. Turner, and R. P. Anderson. Measurement and extinction of vector light shifts using interferometry of spinor condensates. arXiv:1607.06898.
[2] S. Chu, J. E. Bjorkholm, A. Ashkin, and A. Cable. Phys. Rev. Lett. 57, 314 (1986).
[3] D. M. Stamper-Kurn, M. R. Andrews, A. P. Chikkatur, S. Inouye, H.-J. Miesner, J. Stenger, and W. Ketterle. Phys. Rev. Lett. 80, 2027 (1998)

Apr 19

Seb’s single photon knot paper is out in Scientific Reports

Seb’s first journal article, Optical vortex knots – one photon at a time, was published in Scientific Reports, and is available open access at http://www.nature.com/articles/srep24463

Congratulations Seb!

Mar 11

Lisa Starkey PhD

Lisa Starkey née Bennie submitted her PhD thesis today! Lisa’s thesis is titled Precise engineering of the Bose–Einstein condensate wavefunction using magnetic resonance control.

In 2015 Lisa became the Teaching Administrator in the School of Physics and Astronomy at Monash.

Update: On July 12th, Lisa’s thesis was ratified by Monash Graduate Education. Congratulations, Lisa!

Jan 19

Martijn Jasperse PhD

Dr Martijn Jasperse’s PhD thesis, titled Faraday Magnetic Resonance Imaging of Bose–Einstein Condensates, was ratified on January 19. Congratulations, Martijn!

In July, Martijn moved to Barcelona to work with Morgan Mitchell at ICFO.

Nov 10

Alex Wood PhD

Dr Alex Wood’s PhD thesis, titled Spinor Bose-Einstein condensates in magnetic field gradients, was ratified on November 10. Congratulations, Alex!

Alex has begun a post-doc at the University of Melbourne on observing geometric phases in diamond.