Pulse Sequencer Research Articles

A home-made portable device based on Arduino Uno for pulsed magnetic resonance of NV centers in diamond

We describe the realization of a homemade and portable setup to perform experiments of pulsed magnetic resonance of nitrogen-vacancy (NV) centers in diamonds. The system is fully implemented by using an Arduino Uno board equipped with an AVR microcontroller that is used as a transistor-transistor logic pulse sequencer to drive precise laser and microwave pulses with a resolution of 62.5 ns. The equipment is assembled with low-cost modules on a printed circuit board and placed in a compact box with a volume of 20 × 40 × 10 cm3. The detection system is based on a switched integrator and a photodiode in the vicinity of a diamond substrate and read by oversampling the analog-to-digital converter of Arduino Uno. We characterize a CVD diamond sample by performing the pulsed optically detected magnetic resonance and we show the possibility to perform a coherent manipulation of the electron spin of NV centers by driving Rabi oscillations up to 6 MHz with microwave powers within 1 W. We demonstrate different pulse sequences to study electron spin relaxation and dephasing. Finally, we propose additional modules and an antenna to perform the multifrequency manipulation of the electron spin by microwave and radio-frequency pulses. Compared to the previous studies, our system results in a low-cost setup with significantly reduced complexity, which finds application as a learning module for science education and enables a wider audience to access the magnetic resonance in diamond.

A quantum information processor combination method to reduce latency with qubit readout and control

Physicists build a Quantum Digital Signal Processing (QDSP) framework and Arbitrary Pulse Sequencer 2 (APS2) envisioned for reduced-latency large-scale quantum information processor.

Compact field programmable gate array-based pulse-sequencer and radio-frequency generator for experiments with trapped atoms.

We present a compact field-programmable gate array (FPGA) based pulse sequencer and radio-frequency (RF) generator suitable for experiments with cold trapped ions and atoms. The unit is capable of outputting a pulse sequence with at least 32 transistor-transistor logic (TTL) channels with a timing resolution of 40 ns and contains a built-in 100 MHz frequency counter for counting electrical pulses from a photo-multiplier tube. There are 16 independent direct-digital-synthesizers RF sources with fast (rise-time of ∼60 ns) amplitude switching and sub-mHz frequency tuning from 0 to 800 MHz.

Spin wave diffraction control and read-out with a quantum memory for light

A scheme for control and read-out of diffracted spins waves to propagating light fields is presented. Diffraction is obtained via sinusoidally varying lights shifts and ideal one-to-one mapping to light is realized using a gradient echo quantum memory. We also show that dynamical control of the diffracted spin waves spatial orders can be implemented to realize a quantum pulse sequencer for temporal modes that have high time-bandwidth products. Full numerical solutions suggest that both co-propagating and counterpropagating light shift geometries can be used, making the proposal applicable to hot and cold atomic vapours as well as solid state systems with two-level atoms.

High definition ultrasound of the breast

We propose to develop high definition ultrasound (HD-US) based on a hemispherical synthetic aperture and backscattered sonic waves. This configuration will produce direct three-dimensional maps of ultrasound reflectivity of breast tissues and will display higher signal-to-noise, reduced speckle, and greater spatial resolution compared to ultrasound arrays based on linear or curved planar sampling apertures. Our prototype hemispherical array consists of four interdigitated sub-arrays, each having 128 discrete elements. Currently, this array is used to capture 3D photoacoustic images of the whole breast using a spiral scanning strategy to increase the field of view sufficiently to perform whole-breast screening—photoacoustic mammography (PAM). We will add a multiplexed pulser, pulse sequencer, and T/R switches to capture ultrasound reflectivity data sufficient to form a 3D ultrasound image using the same reconstruction strategy used in PAM. Full 3D image acquisition will take 1.7 min, the same as currently used for PAM data collection. HD-US will be combined with PAM to produce 3D images of soft tissue and microcalcifications. The 3D images will be co-registered with the PAM images of hemoglobin distribution in the breast using a single hemispherical transducer array.

Frequency-locked pulse sequencer for high-frame-rate monochromatic tissue motion imaging

To overcome the inherent low frame rate of conventional ultrasound, we have previously presented a system that can be implemented on conventional ultrasound scanners for high-frame-rate imaging of monochromatic tissue motion. The system employs a sector subdivision technique in the sequencer to increase the acquisition rate. To eliminate the delays introduced during data acquisition, a motion phase correction algorithm has also been introduced to create in-phase displacement images. Previous experimental results from tissue- mimicking phantoms showed that the system can achieve effective frame rates of up to a few kilohertz on conventional ultrasound systems. In this short communication, we present a new pulse sequencing strategy that facilitates high-frame-rate imaging of monochromatic motion such that the acquired echo signals are inherently in-phase. The sequencer uses the knowledge of the excitation frequency to synchronize the acquisition of the entire imaging plane to that of an external exciter. This sequencing approach eliminates any need for synchronization or phase correction and has applications in tissue elastography, which we demonstrate with tissue-mimicking phantoms.

Demonstration of a quantum logic gate in a cryogenic surface-electrode ion trap

We demonstrate quantum control techniques for a single trapped ion in a cryogenic, surface-electrode trap. A narrow optical transition of Sr+ along with the ground and first excited motional states of the harmonic trapping potential form a two-qubit system. The optical qubit transition is susceptible to magnetic field fluctuations, which we stabilize with a simple and compact method using superconducting rings. Decoherence of the motional qubit is suppressed by the cryogenic environment. AC Stark shift correction is accomplished by controlling the laser phase in the pulse sequencer, eliminating the need for an additional laser. Quantum process tomography is implemented on atomic and motional states using conditional pulse sequences. With these techniques we demonstrate a Cirac-Zoller Controlled-NOT gate in a single ion with a mean fidelity of 91(1)%.

Coherent optical pulse sequencer for quantum applications

The bandwidth and versatility of optical devices have revolutionized information technology systems and communication networks. Precise and arbitrary control of an optical field that preserves optical coherence is an important requisite for many proposed photonic technologies. For quantum information applications, a device that allows storage and on-demand retrieval of arbitrary quantum states of light would form an ideal quantum optical memory. Recently, significant progress has been made in implementing atomic quantum memories using electromagnetically induced transparency, photon echo spectroscopy, off-resonance Raman spectroscopy and other atom-light interaction processes. Single-photon and bright-optical-field storage with quantum states have both been successfully demonstrated. Here we present a coherent optical memory based on photon echoes induced through controlled reversible inhomogeneous broadening. Our scheme allows storage of multiple pulses of light within a chosen frequency bandwidth, and stored pulses can be recalled in arbitrary order with any chosen delay between each recalled pulse. Furthermore, pulses can be time-compressed, time-stretched or split into multiple smaller pulses and recalled in several pieces at chosen times. Although our experimental results are so far limited to classical light pulses, our technique should enable the construction of an optical random-access memory for time-bin quantum information, and have potential applications in quantum information processing.

Arterial Vulnerable Plaque Characterization Using Ultrasound-Induced Thermal Strain Imaging (TSI)

Thermal strain imaging (TSI) is demonstrated in two model systems mimicking two potential clinical applications. First, a custom ultrasound (US) microscope produced high-resolution TSI images of an excised porcine coronary artery. Samples were placed in a temperature-controlled water chamber and scanned transversely and longitudinally. Phase-sensitive, correlation-based speckle tracking was applied to map the spatial distribution of temporal strain across the sample. TSI differentiated fatty tissue from water-based arterial wall and muscle with high contrast and a spatial resolution of 60 microm for a 50-MHz transducer. Both transverse and longitudinal TSI images compared well with B-scans of arterial wall structures, including intima, media, adventitia, and overlying fatty tissue. A second model system was used to test the hypothesis that US can produce the heating pattern required for TSI of internal structures. A 2-D phased array with independent drive electronics was combined with a conventional US scanner (iU22, Philips, Bothell, WA) for these studies. This 513-element array, originally designed for the US therapy, acted as the US heat source. To quantify the temporal strain induced by this system, TSI was performed on a homogeneous rubber phantom. TSI temperature estimates were within 3% error for a 3.2 degrees C temperature rise produced within 2 s using a specially designed beamformer and pulse sequencer. The system was then used to produce TSI scanning of an excised kidney containing an intact piece of fat below the collecting system. These images were validated using an magnetic resonance imaging (MRI) pulse sequence designed for lipid quantification. TSI scans matched well MRI scans and histology both anatomically and quantitatively. Finally, to test the potential of US-induced TSI for a significant clinical problem, images were obtained on an excised canine aorta with fatty tissue inside the lumen. Both longitudinal and transversal TSI agreed well with anatomy. These in vitro results demonstrate the potential of high-resolution US-induced TSI with a small temperature change (<1 degrees C) for plaque characterization.

Cassiel: symbolic pulse sequencing

This text presents the motivation and design principles behind the pulse sequencer, a software component used for electronic music composition and performances by Cassiel. The pulse sequencer is a generic, language-based sequence processing engine which can be regarded as an arpeggiator, a sequencer, or anything in between. In fact, arpeggiation and sequencing are special cases of a more general control system. We conclude with some comments about the strengths and weaknesses of the system drawn from several years’ experience in performance projects.

A pulse sequencer and transient nanoammeter system for membrane voltage-dependent capacitance measurements

A highly sensitive system for producing and time-resolving small-signal current transients in bilayer lipid membranes separating two ionic solutions is described. The circuitry can be constructed from inexpensive and readily obtainable electronic components, and may be interfaced with a variety of digital oscilloscopes or data acquisition systems. The system consists of a driver, fast nanoammeter, and timing sequencer. The driver is capable of delivering a stable, very low impedance voltage pulse (−2.0 to +2.0 V) superimposed on a clamping voltage adjustable within the same range. The pulse can be of any width between 500 μs and 5000 s, and can be delayed with respect to an oscilloscope synchronization trigger, which is also provided. The nanoammeter is accurate between 10 pA and 100 mA and has a time resolution of better than 10 μs. The driver and nanoammeter were designed specifically to be stable under the conditions of a highly capacitive load with very high dc resistance, as is typical of a bilayer lipid membrane. The system can be used with either reference or blocking electrodes. Ideal and actual membrane transient response curves, along with noise assessment data, are provided for calibration purposes.

A versatile pulse sequencer for NMR and other applications

The authors describe a pulse sequence generator which they have developed for pulsed NMR applications. It is based around a microprocessor and offers a high standard of performance and versatility while being relatively cheap in terms of hardware. It is the use of the interrupt facility on the microprocessor which enables the generation of a sequence containing any multiplicity of pulses and delays using just two programmable mark-space generators. A digital demultiplexer unit separates and routes the pulses to selected outputs. As well as in NMR this instrument should find applications in other fields of research requiring easily controllable sequences of pulses.

Microcomputer-controlled pulse generator for an electron spin-echo spectrometer

A simple and low-cost microcomputer-controlled pulse generator for an electron spinecho (ESE) spectrometer has been constructed. The generator is composed of a programmable clock pulse generator, a programmable delay generator, and a pulse sequencer. The clock pulse generator supplies trigger pulses to the delay generator with the period ranging from 1 μs to 99,990 s. The delay generator is composed of two commercial time delay modules (Evans Associates Model 4145-2) and an additional 2.5 ns increment delay generator, and supplies reference and delayed pulses to the pulse sequencer. The pulse sequencer generates a series of pulses for the formation of microwave pulses and the detection of ESE signals. Most of the control data for the pulse generator are supplied from a microcomputer (NEC PC-9801). The software for the microcomputer is designed to measure two- and three-pulse echo envelopes and longitudinal relaxation times with the minimum time resolution of 2.5 ns.

A computer-controlled pulse sequeneer for pulsed nmr experiments

A microprocessor-controlled pulse sequencer for diverse pulsed NMR experiments is described. The design is based on a first-in-first-out recycling memory which is loaded and triggered by computer software control. Sixteen output channels are provided for various synchronized functions.

A pulsed NQR-FFT spectrometer for nitrogen-14

A pulsed NQR spectrometer system with fast Fourier transform capabilities operating in the range 0.5 to 5 MHz is described. The transmitter and receiver use a heterodyne configuration to eliminate carrier feedthrough problems present in standard autodyne NQR spectrometers. A unique matching network containing the sample coil allows simultaneous tuning of both the transmitter and the receiver over a two-to-one frequency range. Gating of the system is controlled by a versatile pulse sequencer which can generate Carr-Purcell, Meiboom-Gill modified Carr-Purcell, and spin-locked spin-echo sequences, as well as a standard sequence of π 2 pulses suitable for T 1 measurements or collection of FID signals. The sequencer also generates data collection control signals for a Digilab FTS data system with real-time co-adding and fast Fourier transform capabilities. Examples of experimental results obtained with the spectrometer and data system are presented.

Digital cardiac period meter with DA converter.

ABSTRACTA new type of cardiac period meter, which allows the simultaneous collection of digital and analog records, was designed. The wave‐shaper and the pulse sequencer in a digital counter were modified for the purpose of measuring successive heartbeat intervals. The output terminals of the counter were connected directly to a digital‐to‐analog (DA) converter. The pen‐oscillograph record of the analog output produces a stair‐case waveform characterized by sharp edges and stable horizontal lines.