Alumnus Profile: John Kitching (MS '92, PhD '95)

For John Kitching (MS '92, PhD '95, applied physics), keeping time is not just a necessity for daily life; it's his passion and career focus. Kitching holds several patents in the areas of spectroscopy and quantum systems, and his ground-breaking inventions of the chip-scale atomic clock and chip-scale atomic magnetometer earned him recognition as a 2022 Fellow of both the National Academy of Inventors and IEEE.

ENGenuity spoke with Kitching to learn about his work in the realm of atomic clocks and calibration, his ongoing work at the National Institute of Standards and Technology (NIST), and how his Caltech education shaped his spirit of innovation and invention.

ENGenuity: How would you describe your professional contributions?

John Kitching: I am an applied scientist and I have been working at NIST since I left Caltech in 1995. My research is on developing compact, low-power instruments that combine elements of precision spectroscopy, silicon micro-machining, and photonic systems. The goal of my work is to develop instruments that are going to be of value to the real world.

Historically, my focus has been on atomic clocks. But my work right now spans a range of different technologies from clocks to other types of quantum sensors. I develop devices and instruments that combine precision with low power consumption and a high degree of manufacturability. The basic idea is to have, say, an atomic clock on every desktop or in every cell phone.

I got started with my research group about 20 years ago, a few years after coming to NIST, with the development of something called the chip-scale atomic clock. This is a very small atomic clock about the size of a grain of rice that has a good combination of precision, small size, and low power consumption. That has now turned into a roughly quarter-billion-dollar product and is making an impact across a whole range of different applications from the military to oil and gas exploration and space.

ENGenuity: What exactly is an atomic clock and how is it used?

Kitching: Atoms are currently the best ways of keeping time. An atom functions much like the pendulum in a grandfather clock, but instead of a physical pendulum, it's the oscillation of electrons and nuclei within the atom itself. This oscillation can take the form of electrons moving further away from the nucleus, or it can be the spin of the electron oscillating with respect to the spin of the nucleus. In either case, what you have is something that carries out periodic motion, and because atoms are very simple quantum systems, every cesium atom, for instance, is the same as every other cesium atom. That means that if I build an atomic clock based on cesium here in Boulder, Colorado and you build one based on cesium in Pasadena, California, both clocks will tick at the same rates. In addition, because the fundamental constants that determine that ticking rate are fundamental constants of nature, they don't change in time as far as we know. That means the clock will tick the same in Boulder as it does in Pasadena, and it will tick at the same rate now as it does in ten years.

ENGenuity: What are you currently focused on?

Kitching: The thing that I'm interested right now is a program I started about ten years ago called NIST on a Chip. The idea with NIST on a Chip is to broaden the range of different physical measurements that you could make with chip-scale devices. The foundation is that our entire world relies on calibration. For example, when you go and fill up your car with gas, how do you know that you are getting a gallon of gas? There's something in the gas pump that is measuring the amount of gasoline that is coming out of the pump. We all rely on the fact that those are all calibrated and all read the same because when we buy gasoline, we must know that the gallon we are getting at one gas station is the same as a gallon we get at another gas station. Of course, it's not just gasoline. It's everything from grocery store scales to power to a huge number of other things, and this calibration enables us to trade. If we are going to trade, we need to agree on what the physical quantities are that we are trading.

My research right now is focused on developing chip-scale instruments that would allow us to achieve SI traceability [traceability to the International System of Units] at a low cost and in a way that could be embedded into instruments or into services to keep everything calibrated for the lifetime of the instrument. For example, every gas pump in the country is manually calibrated once a year, so you can imagine the amount of work it takes to keep that going. If you could have a chip that made these calibrations and last the lifetime of the gas pump, then you would not need to manually calibrate them anymore.

ENGenuity: What inspired you to get into science?

Kitching: My father was a physicist, and the thing that I liked about physics was the rigorous way that we could describe the world. I completed my undergraduate degree in physics at McGill University, and then when I came to Caltech, I decided that I wanted to change direction and use my knowledge of physics to impact the real world. I ended up in the Applied Physics department at Caltech, and that was where I was inspired on my current trajectory of innovation and invention.

Then when I came to NIST, I became part of the Time and Frequency division. I was strongly drawn to the idea of clocks and timing. Clocks have been around for millennia. As a species, we have always had this desire for timing things from knowing when we needed to plant our seeds to get crops to grow properly to the cycle of day and night. One of the things that I enjoy about my work is feeling that I am part of a long history of people trying to develop better ways of keeping time and enabling new capabilities. For example, GPS is based on atomic clocks orbiting the Earth on satellites, and precision timing is critical to that very important part of our daily infrastructure.

ENGenuity: How has your Caltech education influenced you?

Kitching: I was a student of Amnon Yariv [Martin and Eileen Summerfield Professor of Applied Physics and Electrical Engineering], and he is one of the great Caltech inventors. The thing that I learned from him is that you can combine elements of things that you know about physics and create novel and interesting devices that could have unique properties.

Being at Caltech and being around some of the brightest people in the world was eye opening for me. At Caltech, there is an idea that no problem is too big to think about, and that we as individuals or teams have the capability of transforming the world in major ways and discovering major new things. Before I came to Caltech, I did not fully appreciate that possibility. Caltech gave me a lot of confidence to tackle big problems in interesting ways and not to be intimidated by the technical challenges that are out there.

Another valuable aspect, and something I did not value enough at the time, is the people that you meet in a place like Caltech go on to help and inform your career for decades afterwards. I still run into people in my career that I knew from my time at Caltech, and we all share this bond of having gone through the Caltech program. The personal connections and the shared intellectual culture that Caltech provided have also been a huge benefit for me.

ENGenuity: What classes at Caltech made a significant impact on you?

Kitching: I remember two fabulous classes, both in physics. One was a class that was taught by Kip Thorne back in the early to mid-1990s when the LIGO [Laser Interferometer Gravitational-Wave Observatory] project was just getting off the ground. Kip had organized this class on LIGO where he brought in a different member of the LIGO team to talk about their part of the LIGO project for each lecture. I remember it being a fabulous class because we were exposed to everything from the general relativity of gravitational wave sources to the suspension systems that held the mirrors. Everything from the most esoteric aspects of astrophysics to the mechanics of how you build things. I remember going to those classes absolutely enthralled, and I still have my notes from that class on my bookshelf. That class brought together so many different aspects of experimental and theoretical physics. Now, LIGO has turned into a spectacularly successful research program.

The other class I remember was a class called "Order of Magnitude Physics" that was taught by Peter Goldreich [Lee A. DuBridge Professor of Astrophysics and Planetary Physics, Emeritus] and Sterl Phinney [Professor of Theoretical Astrophysics]. The goal of the class was to have enough basic knowledge about physics to be able to estimate anything to within an order of magnitude. It was broad but also useful because we encounter broad aspects of physics in everything we do. Being able to figure out a problem by getting a sense of the right magnitude is a skill that I have used in my career ever since.

ENGenuity: What project are you most proud of in your career?

Kitching: My work developing the first chip-scale atomic clock was absolutely a highlight of my career. The fact that this technology has now been commercialized and is making an impact on the world is gratifying to me. I certainly love publishing papers as much as the next person, but seeing something become a real product that matters is an even more gratifying experience. Also, the work that I have been doing over the last decade or so on the NIST on a Chip program stands out, although we are nowhere near finished on that, and I'm not sure it will ever be finished. The vision of calibrating everything in the world is compelling to me. This is something that I think I will work on for the rest of my career and hopefully other people will pick it up even after I'm gone. I'm proud of having initiated that program here at NIST.

Additionally, I am proud of the many people who have come through my research group and gone on to bigger and better things. I meet many of my former students and postdocs periodically and it is always a great delight to see the successes they are having pursuing their own research interests.

ENGenuity: What gives you the most satisfaction in your work?

Kitching: The people that I work with on a daily basis are hugely important to me. If they weren't here, I am not sure that I would continue coming in to work. Aside from that, I am very inspired by an understanding of how things in the world work—that "aha moment" when you are trying to understand a problem or instrument and then suddenly you realize how it works. That is exciting for me.

I am one of the few people in the world who enjoys writing proposals, and the reason I enjoy it is because it gives me a chance to vet ideas and drill down into what the core problems are, and then find innovative ways to solve those problems. That's one thing that I have always enjoyed in my scientific life—taking some challenge, working on it, and developing it to the point where I feel that I have a viable path forward.

ENGenuity: What is your favorite story?

Kitching: One story that I have always loved is the basis for Peter Shaffer's play Amadeus that was a made into a movie in the 1980s. This is a story of the relationship between Wolfgang Amadeus Mozart and one of his rivals at the time, Antonio Salieri. It's a fictionalized story loosely based on fact. Part of the reason I think this story is wonderful is because it has these elements of genius, ambition, and how we interact with our colleagues for better or for worse. There are elements in that story that I think we have all felt as scientists. We all are working in some area, and we are competing, we are ambitious, and there are geniuses in our field. How we adapt our own mentality and our own approach to interacting with those geniuses is always interesting. The story of Amadeus focuses on some of the negative things, but I still find it a very profound statement about the nature of genius and the nature of the people that surround geniuses.

ENGenuity: What is your favorite destination?

Kitching: Right now, I spend a lot of time going to Vancouver, Canada. I spent my high school years in Vancouver, and part of the reason I like going back there is that I still know a lot of people from my time there. Every time I go back, I try to get together with one or two of those people who I have known for many years but haven't interacted with recently. I find it wonderful to check up on where people that I knew have gone and see what path they have taken in their lives. Vancouver is a beautiful city, but I think it is really the people who are there that is the most impactful for me.

ENGenuity: What keeps you up at night?

Kitching: The biggest thing is the declining value of truth in our world. The Caltech motto is "the truth shall make you free" and when I was at Caltech, I kind of rolled my eyes at the motto. What I have realized since leaving Caltech, and especially over the last ten years or more, is that the truth is important. When we lose the truth, bad things happen. If you try to build a bridge without paying attention to the truth, the bridge will fall, and people will suffer. What I see in the world right now is this declining value that we put on truth and honesty. This ranges from politics to the fabric of our society in the United States, and it concerns me greatly. The idea of how we can recover and get back to a place where we can all agree on basic facts is going to be a major challenge for us in the coming years.

ENGenuity: What gets you up in the morning?

Kitching: As I've grown throughout my career, I have seen the value of imagining things and believing in things that are not yet possible. I was always a bit of a science fiction fan, as I think many Caltech people are, and the idea of being able to imagine something that could just be science fiction and then work to make that a reality is truly exciting for me. Related to that is the idea of puzzles and solving problems. I do the New York Times crossword every day, and it's a bit of a metaphor for what scientific work is like. You get up in the morning and you are faced with some super interesting puzzles to solve. That has always excited me throughout my career and continues to do so.