Spin Centres in Crystals for Scalable Quantum Technology

Spin centres in crystals are promising candidates for the creation of quantum sensing, computing, and communication technology [1].

Nitrogen-vacancy (NV) centres in diamond have risen to prominence as quantum sensors as they offer biocompatibility, bright photoluminescence, and long spin coherence at room temperature [2]. Developing these systems towards practical sensor devices is underway, but the collection of photoluminescence for optical readout remains too cumbersome and costly for many applications. Recently, it has been shown that their quantum state can also be read out electrically, which constitutes a large step towards compact, integrated devices. This method has been used to measure the state of a single electronic spin, and even to observe the spin state of a single atomic nucleus [3,4].

Communication between such spin centres can be used to build quantum networks and quantum computers. The optical transitions of NV centres are not ideally suited for this purpose, mainly because of their emission in the visible domain which leads to scattering losses and is not compatible with optical fiber networks [1]. Other spin centres are therefore under investigation which may be better suited for such applications, such as the vanadium centres in silicon carbide (SiC). This family of defects is of great interest because of their telecom-range optical transitions and their rich spin structure [5]. Progress on investigations of the optical and spin properties of vanadium in SiC will be presented, with a view towards spin polarization and control, integration into photonic structures such as high-finesse microcavities, and the creation of long-distance quantum networks [6–8]. A long spin relaxation lifetime is one of a set of advantageous features which make vanadium a strong contender for such applications [9].

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[2] T. Zhang et al., Toward Quantitative Bio-Sensing with Nitrogen–Vacancy Center in Diamond, ACS Sens. 6, 2077 (2021).

[3] P. Siyushev, M. Nesladek, E. Bourgeois, M. Gulka, J. Hruby, T. Yamamoto, M. Trupke, T. Teraji, J. Isoya, and F. Jelezko, Photoelectrical Imaging and Coherent Spin-State Readout of Single Nitrogen-Vacancy Centers in Diamond, Science 363, 728 (2019).

[4] M. Gulka, D. Wirtitsch, V. Ivády, J. Vodnik, J. Hruby, G. Magchiels, E. Bourgeois, A. Gali, M. Trupke, and M. Nesladek, Room-Temperature Control and Electrical Readout of Individual Nitrogen-Vacancy Nuclear Spins, Nat Commun 12, 4421 (2021).

[5] L. Spindlberger, A. Csóré, G. Thiering, S. Putz, R. Karhu, J. U. Hassan, N. T. Son, T. Fromherz, A. Gali, and M. Trupke, Optical Properties of Vanadium in 4 H Silicon Carbide for Quantum Technology, Phys. Rev. Applied 12, 014015 (2019).

[6] C. M. Gilardoni, I. Ion, F. Hendriks, M. Trupke, and C. H. van der Wal, Hyperfine-Mediated Transitions between Electronic Spin-1/2 Levels of Transition Metal Defects in SiC, New J. Phys. 23, 083010 (2021).

[7] B. Tissot and G. Burkard, Hyperfine Structure of Transition Metal Defects in SiC, Phys. Rev. B 104, 064102 (2021).

[8] J. Fait, S. Putz, G. Wachter, J. Schalko, U. Schmid, M. Arndt, and M. Trupke, High Finesse Microcavities in the Optical Telecom O-Band, Appl. Phys. Lett. 119, 221112 (2021).

[9] T. Astner, P. Koller, C. M. Gilardoni, J. Hendriks, N. T. Son, I. G. Ivanov, J. U. Hassan, C. H. van der Wal, and M. Trupke, Vanadium in Silicon Carbide: Telecom-ready spin centres with long relaxation lifetimes and hyperfine-resolved optical transitions, arXiv:2206.06240 (2022).