Abstract
Flopping mode qubits in double quantum dots (DQDs) allow for coherent spin-photon hybridization and fast qubit gates when coupled to either an alternating external or a quantized cavity electric field. To achieve this, however, electronic systems rely on synthetic spin-orbit interaction (SOI) by means of a magnetic field gradient as a coupling mechanism. Here we theoretically show that this challenging experimental setup can be avoided in heavy-hole (HH) systems in germanium (Ge) by utilizing the sizeable cubic Rashba SOI. We argue that the resulting natural flopping mode qubit possesses highly tunable spin coupling strengths that allow for one- and two-qubit gate times in the nanosecond range when the system is designed to function in an optimal operation mode which we quantify.
Highlights
The potential of implementing and manipulating physical qubits in semiconductor systems was first recognized in the late twentieth century [1,2,3,4,5] and has since been demonstrated in countless experiments [6,7,8]
We show that HHs in Ge can form a natural flopping mode qubit, i.e., one that does not require synthetic spin-orbit interaction (SOI) via a magnetic field gradient
Analysing the form of the novel terms, we find that the quantity χ acts as an intrinsic magnetic field gradient of strength 2χ
Summary
The potential of implementing and manipulating physical qubits in semiconductor systems was first recognized in the late twentieth century [1,2,3,4,5] and has since been demonstrated in countless experiments [6,7,8]. Among the most promising candidates for a platform for flopping-mode spin qubits are electrons in Silicon and Carbon DQDs, which have seen detailed studies regarding their performance and decoherence properties [30,31,32,33,34,35,36] In these systems, a magnetic field gradient perpendicular to the DQD axis is applied to achieve a coupling between bonding and antibonding states of different spin. We find terms describing spin-flip tunneling and intradot spin flips, which are induced by the SOI and the effect of excited orbitals These terms allow for spin couplings in the bonding state when the system is coupled to a classical alternating or a quantized cavity electric field. VI provides a conclusion and an outlook on possible future research concerning natural flopping mode qubits
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