Improving the sensitivity of electron paramagnetic resonance to identify decoherence time limitation mechanisms in quantum computers

Quantum computing technology is a promising candidate to solve problems that classical computers cannot. Perhaps its most critical challenge is significantly reducing the error rates caused by the quantum system losing coherence due to the unintentional entanglement with its environment, known as decoherence. The decoherence time limitations in quantum computers increases with the number of qubits implemented. A primary source of error in multiple quantum systems is flux noise. Recent work has shown that the majority of flux noise is due to paramagnetic point defects at and near the surfaces on which the qubits reside. Conventional electron paramagnetic resonance (EPR) is a prime candidate to detect these defects but lacks the sensitivity to provide chemical and physical information of the defects. We demonstrate an EPR spectrometer which utilizes a non-resonant probe which improves the state-of-the-art EPR sensitivity by four orders of magnitude with a high spatial resolution of roughly 10⁴ μm² and scanning capability. Our work exploits an idea developed for different applications by Campbell et al. The technique offers a pathway for identification of defects which contribute to flux noise thereby providing critical insight into substantially reducing these defects and removing much of the decoherence affecting quantum computers.

Campbell et al., Anal. Chem.(87)9, 2015.

Campbell et al., US Patent 9,507,004, 2016.