Hybrid rare-earth ion superconductor systems for quantum information processing

M. Nilsson, Lars Rippe, Nicklas Ohlsson +2 more

Osama M. Nayfeh

R. McDermott

Osama M. Nayfeh, Vincent Dinh, Brad Liu +3 more

Abstract : Rare-earth ions are useful for the implementation of quantum memory. In particular, the energy levels and magnetic/spin properties of select ions may enable storage of quantum states. Also, the optical activity may enable optical read-out techniques and optical transmission of qubit states. In addition, the energy levels of ions can be used for designing superconducting qubits where the ionic configuration tunes the Hamiltonian for quantum computing. In the more near term, ions embedded in superconductor heterostructure can be used to implement cryogenic memory for superconducting digital computing. Our concept involves embedding rare-earth ions in superconductor devices to provide a low dissipation environment and access to the systems Hamiltonian. In this report we show results and success in integrating rare-earth neodymium by ion implantation in thin films of niobium and niobium-based heterostructure devices. We model the ion implantation process and confirm the concentration of the neodymium in niobium by energy dispersive X-ray (EDX) spectroscopy in a scanning electron microscope (SEM). We study the effect of optical illumination and magnetic stimulus on the transport of the devices at room temperature, as it is important to understand the films and devices so they can properly designed and optimized for utility as quantum memory. We find that the magnetic field has a strong effect on the response. We also find that the selectivity in the optical effect when using a broadband halogen lamp in comparison to a light emitting diode (LED) with selectivity in the excitation wavelength, reinforces the role of the magnetic and optically active Nd rare-earth ions on the device response.

Senthil Kumar Kuppusamy, Diana Serrano, Aline M. Nonat +5 more

The success of the emerging field of solid-state optical quantum information processing (QIP) critically depends on the access to resonant optical materials. Rare-earth ions (REIs) are suitable candidates for QIP protocols due to their extraordinary photo-physical and magnetic quantum properties such as long optical and spin coherence lifetimes ($T_2$). However, molecules incorporating REIs, despite having advantageous properties such as atomically exact quantum tunability, inherent scalability, and large portability, have not yet been studied for QIP applications. As a first testimony of the usefulness of REI molecules for optical QIP applications, we demonstrate in this study that narrow spectral holes can be burned in the inhomogeneously broadened $^5$D$_0\to^7$F$_0$ optical transition of a binuclear Eu(III) complex, rendering a homogeneous linewidth ($Γ_h$) = 22 $\pm$ 1 MHz, which translates as $T_2 = 14.5$ $\pm$ 0.7 ns at 1.4 K. Moreover, long-lived spectral holes are observed, demonstrating efficient polarization of Eu(III) ground state nuclear spins, a fundamental requirement for all-optical spin initialization and addressing. These results elucidate the usefulness of REI-based molecular complexes as versatile coherent light-spin interfaces for applications in quantum communications and processing.

Philippe Goldner, Alban Ferrier, O. Guillot-Noël