A fast Ge spin qubit read-out with RF reflectometry

Exceptional properties such as long coherence times, fault tolerant fidelities, fast and high fidelity state read-out, together with CMOS integration capabilities set spin-qubits amongst the top players in the race towards the quantum computer.

Currently, those exceptional characteristics are scattered among different spin-qubit platforms. This is where hole spin qubits in Ge could come up as a solution. Due to their large spin-orbit coupling and a weak overlap with nuclear spins they allow fast and fully electrical qubit state manipulation in combination with relatively long coherence times. In the first part of my talk I will speak about the singlet-triplet qubit in planar Ge that I implemented during my postdoc/quantum engineer role in the group of Georgios Katsaros at ISTA. Exploiting the large and tunable out-of-plane g-factors allowed X-rotation frequency of up to 600 MHz, and a quality factor exceeding 200 at a magnetic field of only 10 mT.  The reported results not only compete with the state of the art spin qubits but pave also the way for on-chip co-integration with superconducting technology. The focus will be mainly on the measurement protocol/setup with the accent on the RF reflectometry qubit state read-out technique. I will elaborate on the reflectometry setup optimization for achieving higher spin read-out sensitivities.