Abstract
We investigate the effects of a novel approach to diamond nanofabrication and nitrogen vacancy (NV) center formation on the optical linewidth of the NV zero-phonon line (ZPL). In this post-implantation method, nitrogen is implanted after all fabrication processes have been completed. We examine three post-implanted samples, one implanted with $^{14}$N and two with $^{15}$N isotopes. We perform photoluminescence excitation (PLE) spectroscopy to assess optical linewidths and optically detected magnetic resonance (ODMR) measurements to isotopically classify the NV centers. From this, we find that NV centers formed from nitrogen naturally occuring in the diamond lattice are characterized by a linewidth distribution peaked at an optical linewidth nearly two orders of magnitude smaller than the distribution characterizing most of the NV centers formed from implanted nitrogen. Surprisingly, we also observe a number of $^{15}$NV centers with narrow ($<500\,\mathrm{MHz}$) linewidths, implying that implanted nitrogen can yield NV centers with narrow optical linewidths. We further use a Bayesian approach to statistically model the linewidth distributions, to accurately quantify the uncertainty of fit parameters in our model, and to predict future linewidths within a particular sample. Our model is designed to aid comparisons between samples and research groups, in order to determine the best methods of achieving narrow NV linewidths in structured samples.
Highlights
Excellent spectral properties and low spectral noise are a necessity for most quantum communications and entanglement protocols
The zero-phonon line (ZPL) wavelengths for sample A are tightly clustered, and the sample exhibits no clear relationship between ZPL wavelength and optical linewidth
Binning the linewidths and color coding them according to the sample location [see Fig. 2(b)] reveals that there are two distinct populations of nitrogen vacancy (NV) centers: Those with narrow linewidths, and those with broad linewidths
Summary
Excellent spectral properties and low spectral noise are a necessity for most quantum communications and entanglement protocols. Whether the goal is to entangle atoms in different cities [1], to relay quantum information across vast distances through a communications channel [2], to couple a qubit to a photonic cavity [3,4], or to study the interference between two qubits [5], some of the biggest successes of quantum technology rely on quantum sources that are spectrally stable [6]. The nitrogen vacancy (NV) center in diamond has been successful in a variety of quantum information experiments, as the NV spin can be coupled to its optical degree of freedom [3,5,6,7,8]. Broader optical linewidths can be tolerated: A 100 MHz linewidth is acceptable for a decent microcavity [4], and two-photon interference has been shown using an NV center with an inhomogeneous linewidth as broad as 480 MHz [5]
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