Utilizing Clock-Transition Inhomogeneity in Molecular Nanomagnets and Silica Defect Centers for Holographic Microwave-Pulse Storage

Quantum memories are a crucial component in quantum information science, with applications in quantum computation, communication, and the development of quantum networks. Electron-spin ensembles are promising storage media for quantum information due to their scalability, flexibility, and the ease with which they can be manipulated with pulsed microwaves.¹ Inhomogeneous broadening within these systems can be leveraged for quantum memory applications. We investigate two systems – defect centers in borosilicate glass and Cr₇Mn molecular rings – where spin clock transitions have been found to enhance coherence times.^2,3 In each system, the clock transitions have broad inhomogeneities in frequency and limited spectral diffusion, increasing the potential to store information in the form of microwave pulses using multiple excitation frequencies. This feature affords the flexibility to retrieve stored pulses of different frequencies at will through the choice of refocusing-pulse frequency. We demonstrate storage and controlled retrieval from sub-ensembles at the clock transition in these systems. While the echo amplitudes are primarily limited by the systems’ coherence times, phase coherence is remarkably well preserved.

¹ V. Ranjan et al., Phys. Rev. Lett. 125, 210505 (2020)

² C. Collett et al., Magnetochemistry 5, 1 (2019)

³ B. Sheehan et al., arXiv:2407.21214 (2024)