Across various qubit platforms, a common trade-off persists: increasing coherence comes at the cost of operational speed, reflecting the notion that protecting a qubit from its noisy surroundings also limits control over it. This speed-coherence dilemma limits qubit performance across various technologies.

In this work, we show how this can be circumvented: we demonstrate a hole spin qubit in a Ge/Si core/shell nanowire that triples its Rabi frequency while simultaneously quadrupling its Hahn-echo coherence time, boosting the Q-factor by a factor of 12. This is enabled by the direct Rashba spin-orbit interaction, emerging from heavy-hole-light-hole mixing through strong confinement in two dimensions. Tuning a gate voltage causes this interaction to peak, providing maximum drive speed and a point where the qubit is optimally protected from charge noise, allowing speed and coherence to scale together

Breaking the speed-coherence trade-off makes it possible to boost fidelity and speed of one- and two-qubit gates. This concept can potentially be expanded to planar arrays of hole or electron spin qubits as well. In this regime, the coupling to a microwave resonator is also predicted to be both strong and coherent. Our proof-of-concept shows that careful dot design can overcome a long-standing limitation, offering a new approach towards building high-performance, fault-tolerant qubits.

Collaboration between the Ares group (Oxford University), Bakkers group (TU Eindhoven) and Zumbühl group (University of Basel), supported by the the NCCR SPIN of the Swiss NSF, the Swiss Nanoscience Institute (SNI), the Georg H. Endress Foundation, the EU H2020 European Microkelvin Platform (EMP) project (Grant No. 824109) and the TOPSQUAD project (Grant No. 862046).

Compromise-free scaling of qubit speed and coherence
Miguel J. Carballido, Simon Svab, Rafael S. Eggli, Taras Patlatiuk, Pierre Chevalier Kwon, Jonas Schuff, Rahel M. Kaiser, Leon C. Camenzind, Ang Li, Natalia Ares, Erik P.A.M Bakkers, Stefano Bosco, J. Carlos Egues, Daniel Loss, Dominik M. Zumbühl, Nature Communications 16, 7616 (Aug 15, 2025), manuscript pdf SOM pdf