Quantum networks offer the ability to employ more secure protocols than modern communication. For advanced quantum network protocols, qubits containing states that can be optically accessed and can store quantum properties for a long time are encouraging. Spin qubits in Si offer long coherence times, and the maturated micro- and nanofabrication techniques can be exploited to miniaturise quantum devices. Additionally, modern telecommunication networks also make use of Si-based materials because of the efficient optical confinement achievable. To minimise the photon losses and leverage on these well-established telecommunication networks, the photons excited from the spin states in Si should emit within the telecommunication C-band. In this sense, Er3+ ions in Si form an attractive qubit system because of the Er3+ ions exhibiting a spin transition that can be accessed by photons with frequencies within the telecommunication C-band.
In this seminar, the optical and spin properties of Er3+ ions in Si are presented with the aim to create an interface between a spin qubit and a flying qubit. Here, the optical measurements include the extraction of inhomogeneous and homogeneous broadening of Er3+ ions in Si over various samples, observing linewidths down to less than 100 MHz and 500 kHz, respectively. The low Er3+ density in natural Si samples showed characteristics of long-lived electron spin states with spin-lattice relaxation times of over 10 s and a Rabi oscillation decay of over a microsecond. For the electron spin of an Er3+ site in a nuclear-spin-free Si crystal, a Rabi oscillation decay up to 50 us was measured, and by employing a Hahn echo sequence, a coherence time up to 1.1 ms was measured. These optical and spin properties establish that Er3+ ions in Si exhibit fundamentally promising properties for quantum networks.
Ian Berkman received his BSc in Physics in 2015 at Leiden University in the Netherlands. Following, Ian graduated in 2018 from TU Delft with a MSc in Applied Physics and a specialisation in quantum nanoscience. For his doctorate degree, Ian investigated the intrinsic properties of erbium in silicon with the aim of using Er3+:Si systems for quantum communication, as well as quantum computation purposes at the University of New South Wales, Sydney, in Prof. Sven Rogge's group. Ian submitted his PhD thesis in October 2022 and continues working as a postdoctoral researcher on Er3+:Si in Prof. Sven Rogge's group.