Electron spins in solid-state matrices are among the most studied platforms for quantum technologies, offering sufficiently long coherence times. Various spin systems have been extensively explored – some excel in isolation (e.g., donor spins [1]), while others provide better control (e.g., quantum dots [2]). A novel promising candidate for a spin-based spin qubit platform is an encapsulated atomic hydrogen in polyhedral oligomeric silsesquioxane (POSS) cages [3, 4]. This system exhibits a clock transition, making it insensitive to first-order external magnetic field fluctuations, a property that can be leveraged to increase coherence time. Here, we employ electron paramagnetic resonance (EPR) spectroscopy to study the coherence and relaxation properties of encapsulated atomic hydrogen in POSS cages at low temperature and at both X-band (\(\sim\) 9.5 GHz) and at the famous 1420 MHz hydrogen line. Additionally, we describe the specialized equipment developed for this study: a custom L-band (1 – 2 GHz) EPR probe with low noise amplifiers cooled in closed-cycle He cryostat [5] and employment of a home-built EPR spectrometer capable of operating up to 12 GHz frequencies.
EPR INVESTIGATION OF ENCAPSULATED ATOMIC HYDROGEN IN POSS CAGES FOR QUANTUM TECHNOLOGIES
Justinas Turčak1, Gediminas Usevičius1, Vidmantas Kalendra1, Jūras Banys1, George Mitrikas2, Mantas Šimėnas1
1 Faculty of Physics, Vilnius University, Sauletekio 9, LT-10222 Vilnius, Lithuania
2 Institute of Nanoscience and Nanotechnology, NCSR Demokritos, Athens 15310, Greece
[1] G. Wolfowicz et al., "Atomic clock transitions in silicon-based spin qubits," Nature Technology, vol. 8, pp. 561-564, 2013.
[2] D. Loss and D. P. DiVincenzo, "Quantum Computing with Quantum Dots", Physical Review A, vol. 57, no. 1, pp. 120–126, 1998.
[3] G. Mitrikas and S. Menenakou, "Electron spin relaxation properties of atomic hydrogen encapsulated in octavinyl POSS cages," Physical Chemistry Chemical Physics, vol. 22, no. 28, pp. 15751–15758, 2020.
[4] G. Mitrikas, "Encapsulated Atomic Hydrogen in Octamethyl-POSS Cages: A Pulsed EPR Study," ChemPlusChem, vol. 89, no. 11, p. e202400146, 2024.
[5] M. Šimėnas et al., "A sensitivity leap for X-band EPR using a probehead with a cryogenic preamplifier," Journal of Magnetic Resonance, vol. 322, p. 106876, 2021.