Suppressing qubit dephasing using real-time Hamiltonian estimation

TLDR

Unwanted interaction with a fluctuating environment causes decoherence, the main obstacle to scalable quantum computing, and while engineering, error correction, and dynamical decoupling can mitigate it, they typically add experimental complexity. The study aims to enhance qubit coherence by employing real‑time Hamiltonian parameter estimation. A rapidly converging Bayesian method is used to precisely measure the singlet‑triplet splitting in a spin qubit faster than the nuclear bath fluctuates, enabling continuous adjustment of control parameters. This approach extends the inhomogeneously broadened coherence time T2* from tens of nanoseconds to over 2 µs, is compatible with arbitrary qubit operations, and serves as a natural complement to quantum error correction for improving many qubit platforms.

Abstract

Unwanted interaction between a quantum system and its fluctuating environment leads to decoherence and is the primary obstacle to establishing a scalable quantum information processing architecture. Strategies such as environmental and materials engineering, quantum error correction and dynamical decoupling can mitigate decoherence, but generally increase experimental complexity. Here we improve coherence in a qubit using real-time Hamiltonian parameter estimation. Using a rapidly converging Bayesian approach, we precisely measure the splitting in a singlet-triplet spin qubit faster than the surrounding nuclear bath fluctuates. We continuously adjust qubit control parameters based on this information, thereby improving the inhomogenously broadened coherence time (T2*) from tens of nanoseconds to >2 μs. Because the technique demonstrated here is compatible with arbitrary qubit operations, it is a natural complement to quantum error correction and can be used to improve the performance of a wide variety of qubits in both meteorological and quantum information processing applications.