arXiv subjects

J. N. Becker

Publications and source records attributed to J. N. Becker.

4 recordsLinked to original sources

arXiv2026

A transition-metal qubit in diamond with all-optical control and millisecond quantum memory

Quantum networks require qubits that combine efficient optical access, coherent control, and long-lived quantum memory, but realizing all three in one scalable platform remains a central bottleneck. Diamond color centers are leading candidates, yet widely studied defects retain tradeoffs among these capabilities. Here, we show that transition-metal defects in diamond provide a distinct route beyond these platforms by combining spin-orbit protected ground-state coherence, all-optical control, and near-infrared emission. Using a single nickel-vacancy (NiV$^-$), we demonstrate an all-optically controlled diamond spin qubit with coherence exceeding one millisecond at 1.65 K, compatible with compact closed-cycle cryogenics. We implement Raman Rabi oscillations and Ramsey interferometry and use all-optical dynamical decoupling to extend coherence from $T_2^*$ = 371 ns to $T_2^{CPMG-4}$ = 1.27 ms, establishing NiV$^-$ as a deployable diamond spin-photon interface.

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arXiv2024

Lifetime-Limited and Tunable Emission from Charge-Stabilized Nickel Vacancy Centers in Diamond

The negatively charged nickel vacancy center (NiV$^-$) in diamond is a promising spin qubit candidate with predicted inversion symmetry, large ground state spin orbit splitting to limit phonon-induced decoherence, and emission in the near-infrared. Here, we experimentally confirm the proposed geometric and electronic structure of the NiV defect via magneto-optical spectroscopy. We characterize the optical properties and find a Debye-Waller factor of 0.62. Additionally, we engineer charge state stabilized defects using electrical bias in all-diamond p-i-p junctions. We measure a vanishing static dipole moment and no spectral diffusion, characteristic of inversion symmetry. Under bias, we observe stable transitions with lifetime limited linewidths as narrow as 16\,MHz and convenient frequency tuning of the emission via a second order Stark shift. Overall, this work provides a pathway towards coherent control of the NiV$^-$ and its use as a spin qubit and contributes to a more general understanding of charge dynamics experienced by defects in diamond.

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arXiv2023

Transition metal ion ensembles in crystals as solid-state coherent spin-photon interfaces: The case of nickel in magnesium oxide

We present general guidelines for finding solid-state systems that could serve as coherent electron spin-photon interfaces even at relatively high temperatures, where phonons are abundant but cooling is easier, and show that transition metal ions in various crystals could comply with these guidelines. As an illustrative example, we focus on divalent nickel ions in magnesium oxide. We perform electron spin resonance spectroscopy and polarization-sensitive magneto-optical fluorescence spectroscopy of a dense ensemble of these ions and find that (i) the ground-state electron spin stays coherent at liquid-helium temperatures for several microseconds, and (ii) there exists energetically well-isolated excited states which can couple to two ground state spin sub-levels via optical transitions of orthogonal polarizations. The latter implies that fast, coherent optical control over the electron spin is possible. We then propose schemes for optical initialization and control of the ground-state electron spin using polarized optical pulses, as well as two schemes for implementing a noise-free, broadband quantum-optical memory at near-telecom wavelengths in this material system.

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arXiv2021

Gigahertz-Bandwidth Optical Memory in Pr$^{3+}$:Y$_2$SiO$_5$

We experimentally study a broadband implementation of the atomic frequency comb (AFC) rephasing protocol with a cryogenically cooled Pr$^{3+}$:Y$_2$SiO$_5$ crystal. To allow for storage of broadband pulses, we explore a novel regime where the input photonic bandwidth closely matches the inhomogeneous broadening of the material $(\sim5\,\textrm{GHz})$, thereby significantly exceeding the hyperfine ground and excited state splitting $(\sim10\,\textrm{MHz})$. Through an investigation of different AFC preparation parameters, we measure a maximum efficiency of $10\%$ after a rephasing time of $12.5\,$ns. With a suboptimal AFC, we witness up to 12 rephased temporal modes.

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