Directions for miniaturized rare-earth-ion quantum hardware - John Bartholomew

In the past decade, research into the solid-state rare-earth-ion system has compiled a growing resume of critical components for quantum technology. Achievements in this period include an efficient quantum memory for light1, a non-classical light source2, two-qubit gate demonstrations3, and hour-long quantum state storage4. However, for rare-earth-ion quantum technology to markedly outperform any classical equivalent, a miniaturized and integrable architecture must be achieved.
In this talk, I will present progress on two important aspects that will advance the goal of integrated rare-earth-ion quantum hardware. In doing so, I will also introduce the main research directions of Dr Matt Sellars' group at ANU.
One of the aims of our group is to integrate complex photonic circuitry with rare-earth-ion quantum devices on a single crystal'chip'5. Waveguide-based architectures are an appealing approach for achieving this goal. To assess the feasibility of waveguide devices for quantum applications requires a detailed knowledge of the ion's spectroscopic properties at the crystal surface and in highly strained regions near interfaces. Such regions of a Pr3+:Y2SiO5 sample were probed using micron resolution spectroscopic techniques. I will present the results of these experiments and the implications for designing and fabricating waveguides for rare-earth quantum technology.
An alternate route toward miniaturization is to realize devices at the single ion level. However, the extremely low fluorescence rates of rare-earth ions in solid-state hosts (10 – 1000 s -1) makes single ion optical detection a formidable challenge6. I will present techniques that should allow optical readout of the nuclear spin of a single rare-earth ion, and experimental progress towards this aim. These techniques allow the narrow homogeneous linewidths of bulk crystal ensembles to be maintained at the single ion level. This opens a new regime for quantum applications in these materials.
[1] Hedges et al., `Efficient Quantum Memory for Light', Nature 465, 2010.
[2] Ledingham et al., `Experimental Realization of Light with Time-Separated Correlations by Rephasing Amplified Spontaneous Emission', Physical Review Letters 109, 093602, 2012.
[3] Longdell et al., `Demonstration of Conditional Quantum Phase Shift Between Ions in a Solid', Physical Review Letters 93, 130503, 2004.
[4] Zhong et al., `Hyperfine decoherence study of Europium-doped Yttrium Orthosilicate in High Magnetic Fields', Presentation at DPC, 2013.
[5] Marzban et al., `Progress towards the development of rare-earth doped waveguides for quantum communications applications', Presentation at CLEO, 2014.
[6] Utikal et al., `Spectroscopic detection and state preparation of a single praseodymium ion in a crystal', Nature Communications 5, 2014.