Suppressing qubit dephasing using real-time Hamiltonian estimation

TL;DR

This paper demonstrates a real-time Hamiltonian estimation method that significantly enhances qubit coherence times by adaptively counteracting environmental noise, offering a practical approach to improve quantum system stability.

Contribution

It introduces a Bayesian-based real-time Hamiltonian estimation technique that effectively reduces decoherence in spin qubits, compatible with existing quantum operations.

Findings

Coherence time ($T_{2}^{*}$) increased from tens of nanoseconds to over 2 microseconds.

Rapid Bayesian estimation accurately tracks qubit Hamiltonian faster than nuclear bath fluctuations.

Method is compatible with arbitrary qubit operations, enhancing quantum information processing.

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 ($T_{2}^{*}$) from tens of nanoseconds to above 2 $\mu$s and demonstrating the effectiveness of Hamiltonian estimation in reducing the effects of correlated noise in quantum systems. 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 metrological and quantum-information-processing applications.