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An field programmable gate array (FPGA)-based device for charge-state readout of nitrogen-vacancy (NV) center in diamond with nanosecond feedback speed

Runchuan Ye, Yunpeng Zhai, Yushan Liu, Xue Lin, Nanyang Xu

Published Nov 1, 2023• 0 citations
Publisher

Abstract

Ionization of nitrogen-vacancy (NV) center in diamond from the NV− to NV0 state is a destructive process in applications, where a large amount of time is cost for high-fidelity readout. To this end, real-time adaptive feedback would be helpful to improve the readout efficiency. Here, we develop a field programmable gate array-based device that supports complex calculation and real-time feedback at the nanosecond level. This device integrates a time tagger for photon input, a programmable logic arrays for real-time calculation, and a 20-channel pulse streamer for control output. Based on this device, we demonstrate a high-efficiency of real-time charge-state readout. With this device, the signal-to-noise ratio of maximal adaptive-decision-based charge-state readout can be significantly reduced. Moreover, we demonstrate an application of NV− purification with the real-time feedback, where the contrast of spin-state-dependent fluorescence is improved from 31.7% to 35.0%. The device can be easily extended to other quantum systems.

DOI
10.1063/5.0154343

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Ionization of nitrogen-vacancy (NV) center in diamond from the NV− to NV0 state is a destructive process in applications, where a large amount of time is cost for high-fidelity readout. To this end, real-time adaptive feedback would be helpful to improve the readout efficiency. Here, we develop a field programmable gate array-based device that supports complex calculation and real-time feedback at the nanosecond level. This device integrates a time tagger for photon input, a programmable logic arrays for real-time calculation, and a 20-channel pulse streamer for control output. Based on this device, we demonstrate a high-efficiency of real-time charge-state readout. With this device, the signal-to-noise ratio of maximal adaptive-decision-based charge-state readout can be significantly reduced. Moreover, we demonstrate an application of NV− purification with the real-time feedback, where the contrast of spin-state-dependent fluorescence is improved from 31.7% to 35.0%. The device can be easily extended to other quantum systems.
This article introduces a real-time Bayesian estimation algorithm aimed at enhancing the spin readout efficiency of the nitrogen vacancy (NV) center ensemble in the diamond. By integrating both the prior probability distribution and the fluorescence likelihood function, stemming from the implementation of the NV center dynamics model, we offered an innovative solution to surpass the Cramer–Rao lower bound of the readout variance and improve the readout efficiency. The proposed real-time Bayesian estimation readout algorithm was experimentally realized by combining high-performance acquisition and processing hardware, and the Rabi oscillation experiments divulged that the signal-to-noise ratio of our approach was improved by 28.6%. This research illustrates the potential of the Bayesian estimation readout to enhance the NV ensemble's sensing capabilities and support the development of compact and scalable quantum sensors devices on a monolithic platform.
Nitrogen vacancy centers in diamond are among the leading solid state quantum platforms, offering exceptional spatial resolution and sensitivity for applications such as magnetic field sensing, thermometry, and bioimaging. However, in high background environments,such as those encountered in in vitro diagnostics, the performance of NV based sensors can be compromised by strong background fluorescence, particularly from substrates such as nitrocellulose. In this work, we analytically and experimentally investigate the use of pulsed laser excitation combined with time gating techniques to suppress background fluorescence and enhance the signal to noise ratio in NV based quantum sensing, with an emphasis on spin enhanced biosensing. Through experimental studies using mixed ensembles of silicon vacancy and NV centers in bulk diamond, as well as fluorescent nanodiamonds on NC substrates, we demonstrate significant improvements in NV spin resonance visibility, demonstrated by an increase of the SNR by up to 4x, and a resulting measurement time reduction by 16x. The presented technique and results here can help significantly increase the readout efficiency and speed in future applications of NV centers in high background environments, such as in IVD, where the NV centers are used as a fluorescent label for biomolecules.
Nanodiamonds containing nitrogen-vacancy (NV) centers offer a versatile platform for sensing applications spanning from nanomagnetism to in vivo monitoring of cellular processes. In many cases, however, weak optical signals and poor contrast demand long acquisition times that prevent the measurement of environmental dynamics. Here, we demonstrate the ability to perform fast, high-contrast optical measurements of charge distributions in ensembles of NV centers in nanodiamonds and use the technique to improve the spin-readout signal-to-noise ratio through spin-to-charge conversion. A study of 38 nanodiamonds with sizes ranging between 20 and 70 nm, each hosting a small ensemble of NV centers, uncovers complex, multiple time scale dynamics due to radiative and nonradiative ionization and recombination processes. Nonetheless, the NV-containing nanodiamonds universally exhibit charge-dependent photoluminescence contrasts and the potential for enhanced spin readout using spin-to-charge conversion. We use the technique to speed up a T 1 relaxometry measurement by a factor of 5.
A highly integrated, high performance, and re-configurable device, which is designed for the Nitrogen-Vacancy (N-V) center based quantum applications, is reported. The digital compartment of the device is fully implemented in a Field-Programmable-Gate-Array (FPGA). The digital compartment is designed to manage the multi-function digital waveform generation and the time-to-digital convertors. The device provides two arbitrary-waveform-generator channels which operate at a 1 Gsps sampling rate with a maximum bandwidth of 500 MHz. There are twelve pulse channels integrated in the device with a 50 ps time resolution in both duration and delay. The pulse channels operate with the 3.3 V transistor-transistor logic. The FPGA-based time-to-digital convertor provides a 23-ps time measurement precision. A data accumulation module, which can record the input count rate and the distributions of the time measurement, is also available. A digital-to-analog convertor board is implemented as the analog compartment, which converts the digital waveforms to analog signals with 500 MHz lowpass filters. All the input and output channels of the device are equipped with 50 Ω SubMiniature version A termination. The hardware design is modularized thus it can be easily upgraded with compatible components. The device is suitable to be applied in the quantum technologies based on the N-V centers, as well as in other quantum solid state systems, such as quantum dots, phosphorus doped in silicon, and defect spins in silicon carbide.
A simple and convenient design enables real-time three-dimensional position tracking of nitrogen-vacancy (NV) centers in diamond. The system consists entirely of commercially available components (a single-photon counter, a high-speed digital-to-analog converter, a phase-sensitive detector-based feedback device, and a piezo stage), eliminating the need for custom programming or rigorous optimization processes. With a large input range of counters and trackers combined with high sensitivity of single-photon counting, high-speed position tracking (upper bound recovery time of 0.9 s upon 250 nm of step-like positional shift) not only of bright ensembles, but also of low-photon-collection-efficiency single to few NV centers (down to 103 s−1) is possible. The tracking requires position modulation of only 10 nm, which allows simultaneous position tracking and pulsed measurements in the long term. Therefore, this tracking system enables measuring a single-spin magnetic resonance and Rabi oscillations at a very high resolution even without photon collection optimization. The system is widely applicable to various fields related to NV center quantum manipulation research such as NV optical trapping, NV tracking in fluid dynamics, and biological sensing using NV centers inside a biological cell.
Precise readout of spin states is crucial for any approach toward physical realization of a spin-based quantum computer and for magnetometry with single spins. Here, we report a method to strongly improve the optical readout fidelity of electron spin states associated with single nitrogen-vacancy (NV) centers in diamond. The signal-to-noise ratio is enhanced significantly by performing conditional flip-flop processes between the electron spin and the nuclear spin of the NV center's nitrogen atom. The enhanced readout procedure is triggered by a short preparatory pulse sequence. As the nitrogen nuclear spin is intrinsically present in the system, this method is universally applicable to any nitrogen-vacancy center. Besides the readout method, our studies included coherent control over a single nitrogen nuclear spin for the first time.