arXiv subjects

Jeremias Resch

Publications and source records attributed to Jeremias Resch.

4 recordsLinked to original sources

arXiv2026

Watching a Superconducting Coplanar Waveguide Heat Up with a Single Color Center

Single color centers in diamond offer a local probe of their cryogenic environment, providing a direct way to quantify heating in spin-control hardware. Here, we establish a single spectrally stable tin-vacancy (SnV) center as an on-chip thermometer for a diamond membrane and use it to characterize microwave- and radio-frequency-induced heating in a superconducting coplanar waveguide patterned on the same chip. We first calibrate the temperature dependence of the optical C-transition frequency and linewidth from $20\,\mathrm{K}$ down to the few-kelvin regime. At lower temperatures, where the optical response becomes weakly temperature dependent, we use the spin-lattice relaxation time $T_1$ as a complementary thermometer and tune its sensitivity with the transverse magnetic-field component. Applying this local thermometer to a niobium coplanar waveguide, we observe magnetic-field-dependent superconducting breakdown under GHz drive, accompanied by abrupt heating of the diamond. In contrast, at $20\,\mathrm{MHz}$ and $400\,\mathrm{mT}$, relevant for nuclear-spin control, we detect no measurable heating up to the breakdown threshold of $9.4\,\mathrm{dBm}$, corresponding to $B_\mathrm{ac}\sim1.2\,\mathrm{mT}$. These results define a safe operating window for superconducting microwave and RF control structures in diamond-based quantum nodes.

quant-ph↗

arXiv2025

High-fidelity control of a $^{13}$C nuclear spin coupled to a tin-vacancy center in diamond

Nuclear spins near group-IV defects in diamond are promising candidates for quantum memories in quantum network applications. Here, we demonstrate high-fidelity control of a single $^{13}$C nuclear spin coupled to a tin-vacancy (SnV) center in diamond. We perform a combination of optical and microwave pumping to achieve initialization into a combined electro-nuclear spin state with a fidelity of $99.74(3)\,\%$. Harnessing a superconducting waveguide for radio-frequency driving, we demonstrate precise nuclear spin control: Ramsey measurements reveal a coherence time of $T_2^* = 1.5(1)\,$milliseconds, and we use dynamical decoupling to extend it to $1.35(3)\,$seconds. We perform randomized benchmarking, yielding a single-qubit gate fidelity of $99.92(1)\,\%$. This demonstrates a coherent spin-photon system with promising properties for quantum network nodes.

quant-ph↗

arXiv2025

Optically detected nuclear magnetic resonance of coherent spins in a molecular complex

Nuclear magnetic resonance (NMR) is a powerful tool for applications ranging from chemical analysis to quantum information processing. Achieving optical initialization and detection of molecular nuclear spins promises new opportunities - including improved NMR signals at low magnetic field, sensitivity down to the single-molecule level, and full access to atomically precise molecular architectures for quantum technologies. In this study, we report optical readout of coherently controlled nuclear spins in a europium-based molecular crystal. By harnessing ultra-narrow optical transitions, we achieve optical initialization and detection of nuclear spin states. Through radio-frequency driving, we address two nuclear quadrupole resonances, characterized by narrow inhomogeneous linewidths and a distinct correlation with the optical transition frequency. We implement Rabi oscillations, spin echo and dynamical decoupling techniques, achieving nuclear spin quantum coherence with a lifetime of up to 2 ms. These results highlight the capabilities of optically detected NMR (ODNMR) and underscore the potential of molecular nuclear spins for quantum information processing.

quant-ph↗

arXiv2024

Microwave Control of the Tin-Vacancy Spin Qubit in Diamond with a Superconducting Waveguide

Group-IV color centers in diamond are promising candidates for quantum networks due to their dominant zero-phonon line and symmetry-protected optical transitions that connect to coherent spin levels. The negatively charged tin-vacancy (SnV) center possesses long electron spin lifetimes due to its large spin-orbit splitting. However, the magnetic dipole transitions required for microwave spin control are suppressed, and strain is necessary to enable these transitions. Recent work has shown spin control of strained emitters using microwave lines that suffer from Ohmic losses, restricting coherence through heating. We utilize a superconducting coplanar waveguide to measure SnV centers subjected to strain, observing substantial improvement. A detailed analysis of the SnV center electron spin Hamiltonian based on the angle-dependent splitting of the ground and excited states is performed. We demonstrate coherent spin manipulation and obtain a Hahn echo coherence time of up to $T_2 = 430\,\mu$s. With dynamical decoupling, we can prolong coherence to $T_2 = 10\,$ms, about six-fold improved compared to earlier works. We also observe a nearby coupling $^{13}\mathrm{C}$ spin which may serve as a quantum memory. This substantiates the potential of SnV centers in diamond and demonstrates the benefit of superconducting microwave structures.

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