26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Towards Signal and Noise Engineering in Diamond Quantum Spin Readout

Not scheduled

20m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral AIP | Quantum Science and Technology (QST)

Description

Nitrogen-vacancy (NV) centres in diamond are key enablers of room-temperature quantum sensing and computing technologies already targeted for commercialisation by startups around the world (e.g., Quantum Brilliance, Phasor Quantum, Qnami). These technologies face two universal challenges: weak optical input and output spin-readout signals at nanoscale dimensions, and noise that degrades signal quality and contrast.

Utilising an open quantum theoretical framework verified against existing measurements, we recently predicted that both the brightness and visibility of NV magnetometry signals can be enhanced by orders of magnitude via plasmonic control [1]. Several-fold enhancements in brightness and time-domain contrast, together with shorter readout times, are predicted for NV-based spin qubits. Such improvements hold promise for advancing emerging room-temperature quantum technologies reliant on optical interrogation, including sub-cellular-scale magnetometry and qubit readout.

These enhancements occur in specific NV-plasmonic configurations, necessitating computational identification of viable parameter spaces prior to experiment and device design aimed at harnessing them. Our theory equips the community with a tool for such plasmonic engineering.

To complement this, we computationally investigate how nanodiamond size, NV depth, dipole orientation, and surrounding refractive index shape optical excitation, emission, and far-field brightness [2]. This provides design guidance for NV devices in nanoscale settings.

Finally, to progress towards addressing the complementary problem of noise, we are developing an interactive Python toolkit for fitting Markovian and readout-noise models to experimental NV spin-readout data, including magnetometry and relaxometry.

Together, these efforts provide a pathway towards engineering both signal and noise in practical diamond quantum devices.

References:

1. Hapuarachchi, H., Campaioli, F., Jelezko, F., Cole, J.H.,
   “Plasmonically engineered nitrogen-vacancy spin readout”, Optics
   Express 32(13), 22352–22361 (2024).
2. Hapuarachchi, H., Campaioli, F., Cole, J.H., Greentree, A.D., Sun, Q., Annalen der Physik 538(1), e00367 (2026).