Quantum control of spins in diamond: from quantum sensing to quantum thermodynamics

In the rapidly advancing field of quantum technology, quantum defects in diamond have gained attention for their unique combination of properties. With long coherence times, high sensitivity, nanoscale spatial resolution, biocompatibility, and room temperature operation, diamond defects are exceptionally suited for quantum sensing, computing, and communication applications, as well as for exploring fundamental quantum science.

Currently, the most mature use cases of quantum diamond technology are those related to quantum sensing. In the first part of the colloquium, I will show our latest efforts towards developing a quantum imaging platform using ensembles of nitrogen-vacancy (NV) centers in diamond tailored for investigating cardiac tissues. I will also show how strategies based on quantum optimal control [1, 2] and machine learning [3] can offer material-independent strategies to optimize quantum sensing tasks though the design of specialized protocols for manipulating the NV spin state.

Beyond practical quantum technology applications, NV centers in diamond have recently emerged as a novel toolbox for more fundamental investigations. I will discuss how the precise control and long coherence times of NV centers, combined with the ability to tailor their interaction with environment, can be exploited to investigate quantum thermodynamics at the nanoscale, where fluctuations and quantum effects play a significant role. I will show implementations of the two-point measurement (TPM) protocol to reconstruct the statistics of energy fluctuations and verify Jarzynski-like fluctuation relations [4,5,6], and I will discuss different approaches for quantifying the contribution of initial quantum coherence and nonclassical multi-time correlations in (thermo)dynamic processes in closed and open quantum systems [7,8,9,10].

[1] Phys. Rev. X 8, 021059 (2018)
[2] SciPost Phys. 17, 004 (2024)
[3] Mach. Learn.: Sci. Technol.4 (2), 02LT01 (2023)
[4] Physical Review Research 2, 023327 (2020)
[5] New Journal of Physics 13, 065004 (2021)
[6] PRX Quantum 3 (2), 020329 (2022)
[7] npj Quantum Information 9 (1), 86 (2023)
[8] Quantum 7, 1128 (2023)
[9] Physical Review Research 6 (2), 023280 (2024)
[10] npj Quantum Information 10, 115 (2024)