Title: Atomic Sensors and Applications
Speaker: Dr. John Kitching, National Institute of Standards and Technology, USA
This tutorial will cover the design, construction and performance of precision quantum-based sensors using atoms in the vapor phase. The first part of the tutorial will focus on vapor cell instruments, such as atomic magnetometers and NMR gyros. The second part will discuss atom interferometers based on atomic beams or laser-cooled atoms. For each instrument, we will discuss the basic physics underlying the instrument, describe how that physics motives the instrument design, describe experimental and instrumental implications and discuss the experimental and theoretical limits to performance. The talk will also touch on a number of applications of these instruments including inertial navigation, nuclear magnetic resonance and biomagnetics.
Dr. John Kitching is a Fellow and Group Leader in the Time and Frequency Division at the National Institute of Standards and Technology. Over the last fifteen years, he and his group pioneered the development of microfabricated “chip-scale” atomic devices for use as frequency references, magnetometers and other sensors. He is a Fellow of the American Physical Society and has been awarded the Department of Commerce Silver and Gold Medals, the 2015 IEEE Sensors Council Technical Achievement Award, the 2016 IEEE-UFFC Rabi Award and the prestigious 2014 Rank Prize.
Title: Quartz Resonators and Oscillators
Speaker: John R. Vig, Consultant, USA
The subject of quartz crystal resonators and oscillators shall be reviewed. Emphasis will be on those aspects that are of greatest interest to users (as opposed to designers). The discussion will include:
- crystal resonator and oscillator basics;
- the characteristics and limitations of temperature compensated crystal oscillators (TCXOs) and oven controlled crystal oscillators (OCXOs);
- oscillator instabilities: aging, noise, activity dips; and the effects of: temperature, acceleration, radiation, warm-up, atmospheric pressure, magnetic field, and the oscillator circuitry;
- guidelines for oscillator comparison, selection and specification.
Several of the topics are also applicable to other types of oscillators.
John Vig was born in Hungary. He emigrated to the United States while a teenager. He received the B.S. degree from the City College of New York and his Ph.D. degree from Rutgers - The State University, New Jersey, USA. He spent his professional career performing and leading R&D in US government research laboratories - developing high stability quartz crystal resonators, oscillators, and sensors.
He has been awarded 55 patents, is the author of more than 100 publications, including nine book chapters, and his publications have been cited 4500 times. Since 2006, he has been a consultant, mainly to program managers at the US Defense Advanced Research Projects Agency (DARPA) for programs ranging from micro- and nanoresonators to small, low-power atomic clocks.
An IEEE Life Fellow, he served as the 2009 IEEE President and CEO. He founded the IEEE Sensors Council, and served as its founding president. He has also served as the president of the IEEE Ultrasonics, Ferroelectrics, and Frequency Control (UFFC) Society.
He and his wife live in Colts Neck, NJ, USA. Their main hobby is ballroom dancing.
Title: Microwave Atomic Clocks
Speaker: Eric Burt, California Institute of Technology, USA
Microwave atomic clocks are everywhere in society. They range from chip-scale models that can fit into hand-held electronics, to “hardened” units that are flown in space, to laboratory units that reach state of the art levels of precision and accuracy. The term “microwave” corresponds to the wavelength of the radiation used to stimulate the internal atomic transition that forms the basis of the clock. Atomic clock technology grew out of experiments in the 1930’s to investigate and characterize internal atomic structure. It was quickly realized that energy levels of certain internal atomic states, and so the frequency of electromagnetic radiation used to make transitions between them, are exquisitely stable and immune to external perturbations and so might be used as a reference for a frequency standard. The first atomic clocks were based on techniques used in these scientific investigations. Due to the intervening 80+ years of development, microwave atomic clocks enjoy a high degree of sophistication and technical maturity that enables their wide range of applications.
In the first part of this tutorial I will give an overview of how atomic clocks work in general and then describe in detail the underlying physics. Crucial to building atomic clocks is being able to measure their performance, so I will also describe the various metrics used. In the second part of the tutorial, I will give several key examples that represent the range of microwave atomic clock applications. These will include, small chip-scale clocks, engineered space clocks, ultra-stable trapped ion clocks, and accurate laser-cooled fountain clocks. By the end of the tutorial, attendees should be able to understand the strengths and weaknesses of the various clock technologies and to understand talks given at the conference on this topic.
Eric Burt received a B.S. degree with honors in mathematics from the University of Michigan, Ann Arbor, Michigan in 1979, a M.S. degree in physics from the University of Washington, Seattle, Washington in 1990 and a Ph.D. in physics from the University of Washington in 1995. His Ph.D. thesis, supervised by Prof. Warren Nagourney, was in the field of experimental atomic physics on the trapping and laser-cooling of single indium ions. From 1995 to 1997 he was a postdoctoral fellow at the University of Colorado, in Boulder, Colorado working with Carl Wieman and Eric Cornell on experiments with Bose-Einstein condensates including the first experiment to demonstrate a dual-species condensate and the first experiment to demonstrate higher-order (laser-like) coherence in condensate atoms. From 1997 to 2001 he worked at the U.S. Naval Observatory in Washington, D.C. developing a laser-cooled cesium fountain atomic clock. From 2001 to the present he has worked at the Jet Propulsion Laboratory, California Institute of Technology most recently as a Principal Member of Technical Staff. His work at JPL has included development of both ion and laser-cooled neutral atomic clocks and using atomic clocks to place limits on fundamental constant variation. Dr. Burt is a member of the American Physical Society, and the IEEE. He is on the technical program committee for the IEEE Frequency Control Symposium and has served as the chair of that committee as well as vice-chair for group 3 (microwave atomic clocks). He has also served on the steering committee for the APS Topical Group on Precision Measurement and Fundamental Constants.
Title: Fundamental Physics with Atomic Clocks
Speaker: Andrei Derevianko, University of Nevada, USA
Atomic clocks are arguably the most accurate scientific instruments ever build. Modern clocks are astonishing timepieces guaranteed to keep time within a second over the age of the Universe. Attaining this accuracy requires that the quantum oscillator be well protected from environmental noise and that clock perturbations be well controlled and characterized. This opens intriguing prospects of using clocks to study subtle effects, and it is natural to ask if such accuracy can be harnessed for tests of fundamental physics. In this tutorial, I will discuss such applications, including searches for variation of fundamental constants and nascent searches for ultralight dark matter.
Andrei Derevianko is a Hartmann professor of physics at the University of Nevada, Reno. He has authored over 100 refereed publications in theoretical physics. He is a fellow of the American Physical Society, Simons fellow in theoretical physics, and a Fulbright scholar. He earned his Ph.D. at Auburn and did a postdoctoral work at Notre Dame and at the Harvard-Smithsonian Center for Astrophysics. He has been a UNR faculty since 2001. Among a variety of research topics, he has contributed to the development of several novel classes of atomic clocks and precision tests of fundamental symmetries with atoms and molecules. Recent interests include detection of ultralight dark matter with atomic clocks onboard GPS satellites.
Title: Characterization of Clocks and Oscillators
Speaker: Judah Levine, National Institute of Standards and Technology, USA
I will introduce the concepts of accuracy and stability, and I discuss several statistical estimators that are used to characterize the performance of clocks and oscillators. The estimators I will discuss include several versions of the two-sample Allan variance, the Maximum Time Interval Error (MTIE), and the Hadamard variance. I will show how these estimators are derived from a simple physical model of clocks and oscillators. The statistical estimators that are useful in characterizing clocks and oscillators are also useful in characterizing the methods that are used to calibrate and synchronize them. This discussion will lead to methods for designing the optimum strategy for linking a local clock to a remote reference so that the resulting combination has better statistical performance than either the local clock or the network connection alone. I will illustrate these methods by real-world examples.
Judah Levine is a Fellow of the National Institute of Standards and Technology and is the leader of the Network Synchronization Project in the Time and Frequency Division, which is located in the NIST laboratories in Boulder, Colorado. Dr. Levine is responsible for the design and implementation of the time scales AT1 and UTC(NIST), which provide the reference signals for all of the NIST time and frequency services. In addition, he designed and built the servers that support the Automated Computer Time Service (ACTS) and the Internet Time Service, which provide time and frequency information to users in a number of different digital formats. The ACTS service is realized using a number of parallel computers that control a 12-line telephone rotary. The Internet Time Service uses 20 computers, which are located at several sites in the US. These computers receive about 45 000 million (45 billion) requests per day for time stamps in 3 different standard formats. He received his Ph.D. in Physics from New York University in 1966. Dr. Levine is a member of the IEEE and a Fellow of the American Physical Society.
Title: MEMS-Based Oscillators
Speaker: Clark T.-C. Nguyen, University of California at Berkeley, USA
Reference oscillators based on high-Q MEMS resonators have recently become viable alternatives to traditional quartz versions for low-end timing purposes in such applications as televisions and camcorders. Higher end versions of such oscillators suitable for cell phone or other communication applications seem poised to soon hit the market. Indeed, with resonator Q’s exceeding 100,000, research oscillators have posted impressive phase noise performance, even achieving marks that meet the challenging GSM specification while consuming less than 100µW of power. While such devices offer compelling savings in power and space compared to quartz for cell phone applications, they await improvements in aging and temperature stability. In addition, further reductions in power consumption are still desired for future autonomous wireless sensor networks , where nodes would be expected to operate and communicate for long periods without the luxury of replacing their power sources. The integrated circuit nature of MEMS technology that encourages the use of multiple resonators (which often come for practically free) will likely be instrumental towards this goal.
This tutorial presents an overview of the models, circuit topologies, and overall design strategies that have yielded present-day MEMS-based oscillator products and that might propel future such oscillators for higher end applications. The focus will be on capacitive-gap transduced MEMS that presently dominates the MEMS-based timing industry. Time permitting, all aspects will be covered, from fabrication technology, including packaging; to MEMS-based resonator design and mechanical circuit modeling; to oscillator modeling and design, including design strategies to minimize noise and other short term instabilities, e.g., acceleration sensitivity; to methods for nulling drift due to temperature dependence and aging. Two examples of actual demonstrated oscillators—ones a real-time clock, another a GSM reference—will serve as vehicles to drive a practical discussion.
Prof. Clark T.-C. Nguyen received the B. S., M. S., and Ph.D. degrees from the University of California at Berkeley in 1989, 1991, and 1994, respectively, all in Electrical Engineering and Computer Sci¬ences. In 1995, he joined the faculty of the University of Michigan, Ann Arbor, where he was a Professor in the Department of Electrical Engineering and Computer Science up until mid-2006. In 2006, he joined the Department of Electrical Engineering and Computer Sciences at the University of California at Berkeley, where he is presently a Professor and a Co-Director of the Berkeley Sensor & Actuator Center. His research interests focus upon micro electromechanical systems (MEMS) and include integrated micromechanical signal processors and sensors, merged circuit/microme¬chanical technologies, RF communication architectures, and integrated circuit design and technology. In 2001, Prof. Nguyen founded Discera, Inc., the first com¬pany aimed at commercializing communication products based upon MEMS technology, with an initial focus on the very vibrating micromechanical resonators pioneered by his research in past years. He served as Vice President and Chief Technology Officer (CTO) of Discera until mid-2002, at which point he joined the Defense Advanced Research Projects Agency (DARPA) on an IPA, where he served for three-and-a-half years as the Program Manager for 10 different MEMS-centric programs in the Microsystems Technology Office of DARPA. Prof. Nguyen was the Technical Program Chair of the 2010 IEEE Int. Frequency Control Symposium and a Co-General Chair of the 2011 Combined IEEE Int. Frequency Control Symposium and European Frequency and Time Forum. He is an IEEE Fellow and served as a Distinguished Lecturer for the IEEE Solid-State Circuits Society from 2007 to 2009. From 2008 to 2013, Prof. Nguyen served as the Vice President of Frequency Control for the IEEE Ultrasonics, Ferroelectrics, and Frequency Control Society and is presently the President-Elect of the society.
Title: An Introduction to Optical Atomic Clocks
Speaker: Dr. Andrew Ludlow, National Institute of Standards and Technology, USA
Despite their relatively brief history of development, optical atomic clocks have quickly evolved into the most advanced time/frequency standards today. These next-generation standards are being vigorously researched worldwide, with new techniques and even higher levels of performance on the horizon. This tutorial will provide a basic introduction into the optical atomic clock, including a discussion of the different types of optical clocks being developed, their basic components and operation, and important milestones in their development over the last two decades. We will survey the current state-of-the-art in optical clock performance, and highlight present and future research directions. We will also touch upon applications for these high-performance systems, as wells efforts to develop more robust and compact optical clocks for measurements beyond the lab.
Andrew Ludlow is a physicist in the Time and Frequency Division of the National Institute of Standards and Technology (NIST) in Boulder, Colorado. Andrew received a B.S. in physics from Brigham Young University and a Ph.D. in physics from the University of Colorado. He was awarded the 2009 DAMOP Thesis Prize from the Atomic, Molecular, and Optical Physics Division of the American Physical Society for his doctoral research at JILA. Andrew was a National Research Council postdoctoral fellow at NIST until 2010, where he has since remained as a research physicist. His main research interests include the development of optical atomic clocks, cold atom systems for quantum metrology, and ultrastable optical sources and laser interferometry. He currently leads research of the ytterbium optical lattice clock and calcium optical frequency reference at NIST. He has received several awards for his research, including the U.S. Department of Commerce Gold Medal Award, the Young Scientist Award from the European Frequency and Time Forum, and the Presidential Early Career Award. He is a member of the IEEE and American Physical Society, has served on a variety of technical, scientific, and editorial committees, and has published more than fifty scientific journal articles in the field of optical clocks and metrology.
Title: Resonant MEMS for inertial sensing
Speaker: Ashwin Seshia, Cambridge University, UK
Inertial sensors based on microelectromechanical systems (MEMS) technology are increasingly ubiquitous in a variety of consumer electronics, automotive systems, wearable healthcare devices and other high volume applications. However, there is increasing interest in the development of highly accurate MEMS inertial sensors for a variety of emerging applications, for e.g., navigation systems for pedestrians and autonomous vehicles, and seismic and gravity imaging, where the traditional attributes of MEMS (miniaturization and system integration) are combined with scalable transduction principles to enable highly accurate physical measurements. Resonant transducers and oscillatory systems have historically been employed to conduct some of the most precise physical measurements, and resonant approaches to measurement of forces and displacements in MEMS devices have enabled significant advances in accuracy of MEMS inertial sensors in recent years. This progress has been assisted by parallel advances in wafer-level encapsulation techniques, interface circuits, and approaches to mitigate temperature sensitivity, also applied to products in MEMS timing and frequency control. This tutorial will cover the physical principles underlying resonant transduction of inertial forces and contrast these techniques relative to more established transduction principles. Further, applications to navigation-grade resonant accelerometers and mode-matched gyroscopes will be reviewed, and performance metrics benchmarked in comparison to other techniques. The design basis for resonant gyroscopes will be discussed with specific device implementations for whole angle and rate measurements reviewed. Approaches to mitigate sensitivity to environmental effects and drive variations will be discussed, including techniques to address passive immunity through engineered dynamics e.g. mode-localized sensing or engineered nonlinearity. The key physical and practical limitations associated with current approaches will be reviewed, and the interaction between design and fabrication methods will be highlighted.
Ashwin Seshia is the Professor of Microsystems Technology at Cambridge University. He is also a Fellow of Queens’ College and a co-investigator of the Cambridge Centre for Smart Infrastructure and Construction. His research interests are in the domain of micro- and nano-engineered dynamical systems with applications to sensors and sensor systems. Ashwin is a co-founder of two Cambridge University spin-outs (Silicon Microgravity and 8power) formed to translate technologies developed in his research group. He is a Fellow of the Institute of Physics and a Fellow of the Institution of Engineering and Technology. Ashwin serves on the editorial boards of the IEEE Journal of Microelectromechanical systems and the IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.
Title: Phase Noise Metrology
Speaker: Craig Nelson, National Institute of Standards and Technology, USA
Noise is everywhere. Its ubiquitous nature interferes with or masks desired signals and fundamentally limits all electronic measurements. Noise in the presence of a carrier is experienced as amplitude and phase modulation noise. Modulation noise will be covered from its theory, to its origins and consequences. The effects of signal manipulation such as amplification, frequency translation and multiplication on spectral purity will be examined. Practical techniques for measuring AM and PM noise, from the simple to complex will be discussed. Typical measurement problems, including the cross-spectrum anti-correlation, will also be covered.
Craig Nelson is the leader of the Time and Frequency Metrology Group at the National Institute of Standards and Technology. He received his BS in electrical engineering from the University of Colorado in Boulder in 1990. After co-founding SpectraDynamics, a supplier of low phase noise components, he joined the staff at the NIST in 1996. He has worked on the synthesis and control electronics, as well as software for both the NIST-7 and F1 primary frequency standards. He is presently involved in research and development of ultra-stable synthesizers, low phase noise electronics, and phase noise metrology. Current areas of research include optical oscillators, pulsed phase noise measurements and phase noise metrology in the MHz to THz range. He has published over 70 papers and teaches classes, tutorials, and workshops at NIST, the IEEE Frequency Control Symposium, and several sponsoring agencies on the practical aspects of high-resolution phase noise metrology. He was awarded the NIST Bronze Medal in 2012 and the Allen V. Astin Measurement Science Award in 2015 for developing a world-leading program of research and measurement services in phase noise.
Title: Time transfer with optical links
Speaker: Laura Sinclair, National Institute of Standards and Technology, USA
Future optical clock networks have the potential to support a vast array of applications from tests of fundamental physics to coherent sensing to the redefinition of the second. To support the performance of state-of-the-art optical clocks and oscillators, these networks will require optical links. This tutorial will cover methods of optical time and frequency transfer. The wide-ranging parameter space of future optical clock networks necessitates a variety of different methods. We will cover multiple approaches to support frequency transfer, time transfer or even full clock synchronization over either optical fiber or free-space links. Throughout the tutorial, I will highlight relevant applications and recent demonstrations.
Dr. Laura Sinclair is a physicist in the Applied Physics Division at the National Institute of Standards and Technology (NIST) . She received a B.S. from the California Institute of Technology in 2004. A California native, she ventured into snowier parts of the country for her Ph.D., graduating from the University of Colorado, Boulder in 2011. She was a post-doc at NIST Boulder, including as a National Research Council (NRC) post-doctoral fellow, before joining the staff. At NIST, she focuses on the development of optical frequency combs and their applications and is particularly interested in the use of frequency combs to precisely transfer time and frequency information. Recently, Dr. Sinclair was the technical lead of a team that was able to synchronize clocks over kilometers of turbulent air to within femtoseconds. Her comb design serves as the backbone of NIST fiber frequency comb systems for both time transfer across open air paths and precision measurements of airborne contaminants in turbulent environments.
Title: What is Coordinated Universal Time, anyway?
Speaker: Stefania Römisch, National Institute of Standards and Technology, USA
This year is the 30th anniversary of Circular T, the monthly publication by the Time Department of the BIPM (Bureau International des Poids et Mesures) used by the participating national timing laboratories around the world to verify the accuracy of their local realizations of UTC (Coordinated Universal Time). Time is probably the quantity in the SI (International System) that requires the highest degree of coordination among the National Metrology Institutes responsible for implementing its standard quantity, the second, and disseminating the legal time. This is because the local UTCs, UTC(k), are not physical objects that require only occasional calibration, but fleeting pulses in time that occur once and then are gone. Time coordination requires constant monitoring. This tutorial will guide you through all the systems used to generate and disseminate time, including primary frequency standards, time scales, satellite-based time transfer systems, measurement systems and dissemination techniques. Finally, a look will be given at an ever more interconnected world where precision timing is both a powerful enabler and a great vulnerability.
Stefania Römisch is a Group Leader in the Time and Frequency Division at NIST in Boulder, CO. She originally from Torino, Italy and she received her Ph.D. in Electronic Instrumentation in 1998, from Politecnico di Torino, Italy. She was a Guest Researcher at NIST (National Institute for Standards and Technology) in Boulder, CO and then joined the Department of Electrical and Computer Engineering of University of Colorado at Boulder, then worked for a few years as an independent contractor at Spectral Research, LLC, contributing to the Chip-Scale Atomic Clock program funded by DARPA.
She now leads the Atomic Standards Group whose activities include the generation of UTC(NIST), and the use of GPS and TWSTFT to contribute to Universal Coordinated Time. Her research interests span from time scale generation to the calibration of time transfer links and the application of time synchronization technologies to fundamental physics experiments and the development of secure time dissemination. She serves as vice-chair of the technical program committee of the IEEE Frequency Control Symposium, is a 18-year member of the IEEE and a member of the Institute of Navigation.
Title: An Introduction to Global Navigation Satellite Systems
Speaker: Ben Ashman, NASA Goddard Spaceflight Center, USA
Products that rely on Global Navigation Satellite Systems (GNSS) have become an essential part of daily life for millions of people around the world. In addition to enabling navigation, these constellations of satellites and the signals they transmit provide a global, precise timing source, used in everything from electrical power grid phasing to synchronization of financial networks. This tutorial introduces the concept of radio navigation, describes the features of GNSS signals that make navigation possible, and explains how these signals are processed by GNSS receivers. The resulting measurements and error sources, such as atmospheric effects and multipath, are discussed. Then methods are presented for combining these measurements into a position, velocity, and time estimate. The tutorial concludes with a brief status report on the GNSS constellations, space applications and recent flight experiences, and active areas of research.
Benjamin W. Ashman is an Aerospace Engineer in the Navigation and Mission Design Branch (Code 595) at the National Aeronautics and Space Administration (NASA) Goddard Space Flight Center (GSFC) in Greenbelt, Maryland. Dr. Ashman supports numerous space communication and navigation efforts within the agency, most recently as part of the OSIRIS-REx navigation team. His research has primarily been focused on space applications of GPS. He is from Dayton, Ohio, and received his Ph.D. in Electrical Engineering from Purdue University in 2016 and his B.S. in Electrical Engineering from Ohio University in 2010.