Media attention for ion imaging with Fresnel lens

Several media outlets have picked up our press release about ion imaging with Fresnel lenses, including MSN IT. Dave Kielpinski was also interviewed by ABC Gold Coast radio. The press release follows:

Light shines on quantum computing

A world-first experiment at Griffith University has shown quantum computers’ processing speed and accuracy can be increased with the help of tiny lighthouse lenses.

In a paper published this month in the prestigious physics journal Physical Review Letters, the research team at the University's Centre for Quantum Dynamics performed a series of new experiments showing the lenses enable more light to be collected, helping to boost information processing.

Fresnel lens, first developed for use in lighthouses in the 18^th Century, allows light to shine over greater distances making lighthouses visible from far

Griffith physicists are the first to apply this to quantum computing, which could lead to exciting applications in long-distance networking secured by the properties of quantum mechanics.

Associate Professor David Kielpinski said collecting light had been a crucial limit in quantum computing that processed computing problems based on whether the light was on or off.

“The light from a single ion, an electrically charged atom, indicates the result from a computation and its brightness is typically less than a trillionth that of a light bulb,” A/Prof Kielpinski said.

“We successfully used miniature lenses to efficiently image the light emitted from a single ion and this will result in faster processing speeds and lower error rates in quantum computers.”

Australian Postdoctoral Fellow Dr. Erik Streed said the lenses were cost-effective and scaleable.

“The lenses are made with similar methods to computer chips. This means we can use one, 100 or 10,000 lenses with little variation to price,” Dr Streed said.

“Hence, as quantum computers get larger and the number of ions grows, we can increase the number of lenses in order to better read the results processed by ions.”

The study was funded by grants from the Australian Research Council Discovery Project scheme and the researchers are working towards a new era of secure communication over long-distances with quantum computing.

Quantum computers are expected to solve problems far exceeding the capacity of conventional computers.

Wavelength-scale imaging of a single ion

Imaging of Trapped Ions with a Microfabricated Optic for Quantum Information Processing

PRL 106, 010502 (2011)

Trapped ions are a leading system for realizing quantum information processing (QIP). Most of the technologies required for implementing large-scale trapped-ion QIP have been demonstrated, with one key exception: a massively parallel ion-photon interconnect. Arrays of microfabricated phase Fresnel lenses (PFL) are a promising interconnect solution that is readily integrated with ion trap arrays for large-scale QIP. Here we show the first imaging of trapped ions with a microfabricated in-vacuum PFL, demonstrating performance suitable for scalable QIP. A single ion fluorescence collection efficiency of 4.2 \pm 1.5% was observed. The depth of focus for the imaging system was 19.4 \pm 2:4 \mu m and the field of view was 140 \pm 20 \mu m. Our approach also provides an integrated solution for high-efficiency optical coupling in neutral atom and solid-state QIP architectures.

Mode-locked picosecond pulse generation from an octave-spanning supercontinuum

D. Kielpinski and M. G. Pullen
Centre for Quantum Dynamics, Griffith University, Brisbane, Australia

J. Canning and M. Stevenson
Interdisciplinary Photonics Laboratories (iPL), School of Chemistry, University of Sydney, Sydney, Australia

P. S. Westbrook and K. S. Feder
OFS Laboratories, Somerset, New Jersey, USA

Optics Express 17, 20833 (2009)

Abstract: We generate mode-locked picosecond pulses near 1110 nm
by spectrally slicing and reamplifying an octave-spanning supercontinuum
source pumped at 1550 nm. The 1110 nm pulses are near transform-limited,
with 1.7 ps duration over their 1.2 nm bandwidth, and exhibit high interpulse
coherence. Both the supercontinuum source and the pulse synthesis system
are implemented completely in fiber. The versatile source construction
suggests that pulse synthesis from sliced supercontinuum may be a useful
technique across the 1000 - 2000 nm wavelength range.

Recent publications

Frequency stabilization of an ultraviolet laser to ions in a discharge
E. W. Streed, T. J. Weinhold, and D. Kielpinski
Appl Phys Lett 93, 071103 (2008)

Abstract: We stabilize an ultraviolet diode laser system at 369.5 nm to the optical absorption signal from Yb+ ions in a hollow-cathode discharge lamp. The error signal for stabilization is obtained by Zeeman spectroscopy of the 3 GHz wide absorption feature. The frequency stability is independently measured by comparison to the fluorescence signal from a laser-cooled crystal of 174Yb+ ions in a linear Paul trap. We measure a frequency fluctuation of 1.7 MHz over 1000 s and a frequency drift of 20 MHz over 7 days. Our method is suitable for use in quantum information processing experiments with trapped ion crystals.


Scalable, Efficient Ion-Photon Coupling With Phase Fresnel Lenses For Large-Scale Quantum Computing
E.W. Streed, B.G. Norton, J.J. Chapman, and D. Kielpinski
Quant Inform Comp 9, 0203 (2009)

Abstract: Efficient ion-photon coupling is an important component for large-scale ion-trap quantum computing. We propose that arrays of phase Fresnel lenses (PFLs) are a favorable optical coupling technology to match with multi-zone ion traps. Both are scalable technologies based on conventional micro-fabrication techniques. The large numerical apertures (NAs) possible with PFLs can reduce the readout time for ion qubits. PFLs also provide good coherent ion-photon coupling by matching a large fraction of an ion’s emission pattern to a single optical propagation mode (TEM00). To this end we have optically characterized a large numerical aperture phase Fresnel lens (NA=0.64) designed for use at 369.5 nm, the principal fluorescence detection transition for Yb+ ions. A diffraction-limited spot w0 = 350 ± 15 nm (1/e2 waist) with mode quality M2 = 1.08 ± 0.05 was measured with this PFL. From this we estimate the minimum expected free space coherent ion-photon coupling to be 0.64%, which is twice the best previous experimental measurement using a conventional multi-element lens. We also evaluate two techniques for improving the entanglement fidelity between the ion state and photon polarization with large numerical aperture lenses.

Publication: generation of 2 W green light for hydrogen dipole trapping

"Efficient generation of >2W of green light by single-pass frequency doubling in PPMgLN", MG Pullen, JJ Chapman, and D Kielpinski, Appl Opt 47, 1397 (2008)

Abstract: We report 32% efficient frequency doubling of single-frequency 1029nm light to green light at 514.5 nm using a single-pass configuration. A congruent composition, periodically poled magnesium-doped lithium niobate (PPMgLN) crystal of 50 mm length was used to generate a second-harmonic power of 2.3 W. To our knowledge, this is the highest reported power and efficiency achieved in the second-harmonic generation of single-frequency green light in a single-pass configuration.

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Eight Yb+ ions in the Griffith trap.