An integrated device with high performance multi-function generators and time-to-digital convertors

Field-programmable-gate-array based hardware platform for nitrogen-vacancy center based fast magnetic imaging

A nitrogen-vacancy center based scanning magnetic microscope can be used to characterize magnetics at the nanoscale with high sensitivity. This paper reports a field-programmable-gate-array based hardware system that is designed to realize control and signal readout for fast scanning magnetic imaging with a nitrogen-vacancy center. A 10-channel 1 Msps @ 20 bit analog signal generator, a 12-channel 50 ps resolution pulse generator, a 300 Msps @ 16 bit lock-in amplifier with proportional integral derivative control function, and a 4-channel 200 Msps counter are integrated on the platform. A customized acceleration algorithm is realized with the re-configurable field-programmable-gate-array chip to accelerate the imaging speed of the nitrogen-vacancy system, and the experimental results prove that the imaging efficiency can be accelerated by five times compared to the system without the acceleration algorithm. The platform has considerable potential for future applications of fast scanning magnetic imaging.

Multipoint Lock-in Detection for Diamond Nitrogen-Vacancy Magnetometry Using DDS-Based Frequency-Shift Keying

In recent years, the nitrogen-vacancy (NV) center in diamonds has been demonstrated to be a high-performance multiphysics sensor, where a lock-in amplifier (LIA) is often adopted to monitor photoluminescence changes around the resonance. It is rather complex when multiple resonant points are utilized to realize a vector or temperature-magnetic joint sensing. In this article, we present a novel scheme to realize multipoint lock-in detection with only a single-channel device. This method is based on a direct digital synthesizer (DDS) and frequency-shift keying (FSK) technique, which is capable of freely hopping frequencies with a maximum of 1.4 GHz bandwidth and encoding an unlimited number of resonant points during the sensing process. We demonstrate this method in experiments and show it would be generally useful in quantum multi-frequency excitation applications, especially in the portable and highly mobile cases.

A customized control and readout device for vector magnetometers based on nitrogen-vacancy centers

A customized control and readout device, which is developed to perform real-time measurement for vector magnetometers based on nitrogen-vacancy centers, is presented in this paper. A dual-channel analog-to-digital-converter chip, which has a 25 MSa/s sampling rate and a 16 bits amplitude resolution, is integrated for analog signal acquisition. The data processing and the system control are realized using a Xilinx Kirtex-7 field-programmable-gate-array chip. Eight independent lock-in modules, a four-channel proportional-integral-derivative controller, a reference generator, and a vector field reconstruction module are integrated with the Kirtex-7 device in order to perform the real-time vector magnetic field measurement. The device has a bright future to be applied in practical applications.

Mixed-signal data acquisition system for optically detected magnetic resonance of solid-state spins

We report a mixed-signal data acquisition (DAQ) system for optically detected magnetic resonance (ODMR) of solid-state spins. This system is designed and implemented based on a field-programmable-gate-array chip assisted with high-speed peripherals. The ODMR experiments often require high-speed mixed-signal data acquisition and processing for general and specific tasks. To this end, we realized a mixed-signal DAQ system that can acquire both analog and digital signals with precise hardware synchronization. The system consisting of four analog channels (two inputs and two outputs) and 16 optional digital channels works at up to 125 MHz clock rate. With this system, we performed general-purpose ODMR and advanced lock-in detection experiments of nitrogen-vacancy (NV) centers, and the reported DAQ system shows excellent performance in both single and ensemble spin cases. This work provides a uniform DAQ solution for the NV center quantum control system and could be easily extended to other spin-based systems.

A field-programmable-gate-array based high time resolution arbitrary timing generator with a time folding method utilizing multiple carry-chains

A carry-chain based high time resolution arbitrary timing generator, which is fully implemented using field-programmable-gate-array resources, is reported in this paper. The arbitrary timing generator channel operates with two alternative carry-chains to achieve non-dead-time timing sequence generation, and a 45.3 ps time resolution with a 383 ps minimum pulse width can be obtained. The time resolution is further improved to 11.3 ps by employing four parallel carry-chains in a single arbitrary timing generator channel to realize "time folding." The timing generator has a high time stability, and the time uncertainty is below 12 ps within a wide time range of 1 ns-10⁸ ns. The arbitrary timing generator can be used to generate continuous spike timing sequences with a picosecond time resolution.

A high resolution time-to-digital-convertor based on a carry-chain and DSP48E1 adders in a 28-nm field-programmable-gate-array

A field-programmable-gate-array (FPGA) based time-to-digital-converter (TDC), which combines different types of delay chains in a single time measurement channel, is reported in this paper. A new TDC architecture is developed, and both a carry-chain and the DSP48E1 adders, which are integrated inside the FPGA chip, are employed to achieve high resolution time tagging. A single channel TDC has a 3.3 ps averaged bin size, a 5.4 ps single-shot precision, and a maximum sampling rate of 250 MSa/s. The differential-non-linearity of the single TDC channel is -3.3 ps/+24.1 ps, and the integral-non-linearity is within -10.4 ps/+68.6 ps. The TDC performance can be improved by using four TDC channels to measure one input signal, and a 3.4 ps single-shot precision can be obtained. Due to the implementation of the delicated TDC structure, only a small amount of digital resources is required to achieve the picosecond time measurement resolution. Therefore, the reported TDC architecture is suitable for multi-channel applications that require high time resolution measurements of multiple input signals.

Broadband electron paramagnetic resonance spectrometer from 1 to 15 GHz using metallic coplanar waveguide

We report a broadband electron paramagnetic resonance (EPR) spectrometer that operates continuously in the frequency range from 1 to 15 GHz. A broadband metallic coplanar waveguide is utilized as the probe. The system is capable of performing EPR measurements in both continuous wave and pulsed modes. Its performance has been tested with a sample, named 2,2-diphenyl-1-(2,4,6-trinitrophenyl)hydrazyl powder, at room temperature. In the continuous wave mode, the sensitivity of the spectrometer is estimated to be 3.3×10¹² spins/gaussHz at 13 GHz. In the pulsed mode, inversion recovery experiments were carried out to obtain the spin-lattice relaxation time of the sample.

An X-band pulsed electron paramagnetic resonance spectrometer with time resolution improved by a field-programmable-gate-array based pulse generator

We report an X-band pulsed electron paramagnetic resonance (EPR) spectrometer using a Field-Programmable-Gate-Array (FPGA) based pulse generator. The microwave (MW) pulse length and pulse-pulse interval can be adjusted with 50 ps time resolution. A FPGA based pulse generator is utilized to achieve such time resolution. There are eight pulse channels integrated in the pulse generator. Each channel outputs rectangular pulses with 50 ps time resolution. The spectrometer includes a pulse forming unit, where four high-speed PIN diode switches are controlled by the pulse generator to generate MW pulses. A commercial digital storage oscilloscope is used to record the EPR signal. A customized software is developed to control the components of the spectrometer and to perform data processing task. The usefulness of high time resolution is demonstrated by the results of Rabi oscillation.

A pico-second resolution arbitrary timing generator based on time folding and time interpolating

We report a pico-second resolution arbitrary timing generator which is implemented with a field-programmable-gate-array. The arbitrary timing/pattern generator is based on a time folding method which is combined with a delay chain for fine time interpolating. The time folding method can not only break the limitation of sequence time resolution contributed by the minimum chain cell delay but also improve the chain linearity. The arbitrary timing generator which is based on the time folding technique is integrated in a printed-circuit board, and a 5 ps time resolution with enhanced output linearity is obtained. The dynamic range of output pulses from the arbitrary timing generator is from 5 ns to 10 s. In this paper, we describe the principle, the circuit design, and the characterizations of the arbitrary timing generator. We also discuss the improvement of performance in timing generation using the time folding method. The high-performance arbitrary timing generator has a bright future to be used in the applications that require high-resolution timing sequence generation.

High-Resolution Quantum Sensing with Shaped Control Pulses

We investigate the application of amplitude-shaped control pulses for enhancing the time and frequency resolution of multipulse quantum sensing sequences. Using the electronic spin of a single nitrogen-vacancy center in diamond and up to 10 000 coherent microwave pulses with a cosine square envelope, we demonstrate 0.6-ps timing resolution for the interpulse delay. This represents a refinement by over 3 orders of magnitude compared to the 2-ns hardware sampling. We apply the method for the detection of external ac magnetic fields and nuclear magnetic resonance signals of ^{13}C spins with high spectral resolution. Our method is simple to implement and especially useful for quantum applications that require fast phase gates, many control pulses, and high fidelity.