Notch filtering the nuclear environment of a spin qubit

TL;DR

This paper demonstrates that nuclear notch filtering via dynamical decoupling sequences significantly extends the coherence time of spin qubits in gallium arsenide quantum dots, surpassing previous records and enabling more reliable quantum computation.

Contribution

The study introduces nuclear notch filtering as an effective method to suppress nuclear noise across frequencies, substantially improving spin qubit coherence times.

Findings

Achieved a spin coherence time of 0.87 ms using nuclear notch filtering.

Extended coherence times by filtering both low and high frequency nuclear noise.

Surpassed previous coherence time records in GaAs quantum dots.

Abstract

Electron spins in gate-defined quantum dots provide a promising platform for quantum computation. In particular, spin-based quantum computing in gallium arsenide takes advantage of the high quality of semiconducting materials, reliability in fabricating arrays of quantum dots, and accurate qubit operations. However, the effective magnetic noise arising from the hyperfine interaction with uncontrolled nuclear spins in the host lattice constitutes a major source of decoherence. Low frequency nuclear noise, responsible for fast (10 ns) inhomogeneous dephasing, can be removed by echo techniques. High frequency nuclear noise, recently studied via echo revivals, occurs in narrow frequency bands related to differences in Larmor precession of the three isotopes $\mathbf{^{69}Ga}$, $\mathbf{^{71}Ga}$, and $\mathbf{^{75}As}$. Here we show that both low and high frequency nuclear noise can be filtered by appropriate dynamical decoupling sequences, resulting in a substantial enhancement of spin qubit coherence times. Using nuclear notch filtering, we demonstrate a spin coherence time ($\mathbf{T_{2}}$) of 0.87 ms, five orders of magnitude longer than typical exchange gate times, and exceeding the longest coherence times reported to date in Si/SiGe gate-defined quantum dots.