Compromise-Free Scaling of Qubit Speed and Coherence

Abstract

Across leading 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. Here, 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 over an order of magnitude. 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. 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.

Main: 9 pages with 3 display items including references and methods; Supplementary: 17 pages with 10 display items including references

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Cited by in corpus (9)

• Artificial Intelligence for Quantum Computing
• A two-dimensional 10-qubit array in germanium with robust and localised qubit control
• Fully autonomous tuning of a spin qubit
• Optimal operation of hole spin qubits
• A spinless spin qubit
• Electrical readout of spins in the absence of spin blockade
• Variability of hole spin qubits in planar Germanium
• Switchable spin-photon coupling with hole spins in single-quantum dots
• Sweet-spot protection of hole spins in sparse arrays via spin-dependent magnetotunneling