Jun Ye, a renowned physicist, is passionate about more than just keeping time. For him, atomic clocks are a gateway to exploring the fascinating world of quantum physics. These clocks are not just about telling time; they serve as a playground for scientific discovery.
In a cutting-edge lab at the University of Colorado, Jun Ye and his team have constructed the world’s most precise atomic clock. This clock operates by measuring the vibrations of 10,000 atoms. Timekeeping is crucial in our daily lives, influencing everything from GPS navigation to financial networks. But what exactly is time? It’s a precise measurement of atomic vibrations, evolving from ancient sundials to modern atomic clocks.
Atomic clocks rely on the periodic oscillations of electrons around an atom’s nucleus. These oscillations serve as a fundamental unit of time. By measuring these energy levels with extreme precision, scientists can achieve a universal time standard. The NIST F-2, an atomic clock at the National Institute of Standards and Technology in Colorado, exemplifies this precision. It measures the oscillations of cesium atoms, defining a second as 9,192,631,770 cycles.
While current atomic clocks use microwaves, a new generation of clocks is emerging that uses laser light. Optical frequencies oscillate much faster than microwaves, allowing for even more precise time measurements. This shift to optical clocks represents a significant advancement in timekeeping technology.
Building an optical clock is a complex process. Jun Ye’s team is working with elements like strontium and ytterbium, which can tick at higher frequencies. Strontium, for example, is less volatile than cesium and moves at high speeds. To measure time accurately, the team cools these atoms to extremely low temperatures, creating a quantum gas that organizes into an optical lattice.
Once cooled and trapped, the atoms are exposed to a clock laser that matches their energy transition frequency. This frequency, at 430 trillion cycles per second, is so precise that it can maintain time without losing or gaining a second for 15 billion years. Optical atomic clocks outperform microwave clocks by hundreds of times, prompting discussions about when to replace the current cesium standard with these advanced clocks.
Jun Ye’s quest for ultra-precise atomic clocks extends beyond refining time standards. These clocks are invaluable tools for probing the universe’s mysteries, such as gravitational waves and dark matter. By understanding the fabric of space-time, scientists can measure how dark matter influences it. High-precision clocks can detect the subtle changes in time caused by cosmic events.
Ye is optimistic that within the next few decades, we will be able to measure gravitational effects on quantum physics, pushing the boundaries of our understanding of the universe.
Engage in a hands-on workshop where you will build a simple model of an atomic clock. This activity will help you understand the basic principles of atomic oscillations and how they are used to measure time. Collaborate with your peers to explore the components and processes involved in constructing an atomic clock.
Participate in a debate on the implications of quantum physics in modern technology. Discuss how advancements in atomic and optical clocks could influence various fields such as GPS technology, financial systems, and scientific research. This activity will enhance your critical thinking and public speaking skills.
Take a virtual tour of Jun Ye’s lab at the University of Colorado. Observe the cutting-edge technology used in the development of atomic and optical clocks. This immersive experience will provide you with a deeper understanding of the experimental setups and methodologies used in quantum physics research.
Prepare and present a research project on the future of timekeeping. Focus on the transition from microwave to optical clocks and the potential impact on scientific and technological advancements. This activity will improve your research and presentation skills, as well as your ability to synthesize complex information.
Engage in a simulation that demonstrates how high-precision atomic clocks can detect cosmic events such as gravitational waves. Explore the relationship between timekeeping and the universe’s mysteries. This interactive activity will enhance your understanding of the practical applications of atomic clocks in astrophysics.
**Sanitized Transcript:**
Jun Ye: “The reason we get very excited talking about clocks is not just about keeping time, but about exploring the frontier problems of quantum physics. Clocks, I feel, are one part of the human endeavor. You can actually turn that into a quantum physics playground.”
Inside this lab, a team of physicists is working with atoms at high speeds and suspending them in optical traps to measure atomic ticks. “When you walk into our lab, the first thing that comes to your mind is, ‘Oh man, that’s impressive.’”
On this table, Jun Ye and his team at the University of Colorado have built the world’s most precise atomic clock, which gets its ticks from the vibrations of 10,000 atoms. Time is a universal constant in our lives—GPS navigation, power grids, financial networks, and even your commute depend on reliable timekeeping. But have you ever stopped to think about what time actually is? It’s a very precise measurement of ticks, and thanks to technological progress, that “tick” has evolved from the movement of the sun, to a pendulum swing, to the vibrations of a quartz crystal. Since the 1960s, we’ve been on atomic time.
“Inside the atom, electrons move around the nucleus, creating periodic oscillations. We want to use that as our fundamental unit of time. We aim to measure the energy level structure extremely precisely because that’s a constant of nature. If you can measure it precisely, it should be a universal value, and that’s what the atomic clock is all about.”
This is the NIST F-2, an atomic clock at the National Institute of Standards and Technology in Colorado. It’s one of the world’s master clocks, designed to measure the specific oscillations of cesium atoms. Inside, cesium atoms enter the clock’s vacuum chamber, where microwave laser beams push them together into a ball. The lasers toss the ball up, and as it falls back down, it emits photons. The time it takes for the cesium ball to move between two energy levels is 9,192,631,770, which defines a second.
That sounds precise, but a new generation of atomic clocks is on the horizon, using laser light instead of microwaves to divide time into even finer slices. “The reason we want to move from microwave to optical frequency is simple: light frequency oscillates much faster than microwaves. In a blink of an eye, you can have millions or billions of cycles go by with optical frequencies, while microwaves might only have one billion cycles per second. The more cycles you can measure in a fixed time, the fewer fractional mistakes you will make.”
Creating an optical clock is a significant advancement. While this setup may look complex, everything has a purpose. “If we could shrink your size down by a factor of 10 and you walked along those mirrors, it would be like a complete maze of mirrors. Every single mirror on that table serves a specific purpose, allowing us to steer various lasers to interact with the strontium atom.”
Ye and other teams at NIST are building optical clocks based on elements like strontium and ytterbium, which can tick at higher frequencies. “Strontium is in the second column of the periodic table and has two valence electrons. When you have one electron, it’s very volatile; with two, it’s much less volatile compared to cesium atoms. The strontium atom moves at about 300 meters per second, similar to a bullet train. To measure time accurately, we first need to slow them down so they are stationary. We use lasers to cool them down to very low temperatures and load them into an optical trap.”
Ye’s team has cooled strontium atoms to below a microkelvin, turning them into a quantum gas that organizes into an optical lattice. “Once the atoms are cooled and trapped, we turn on the clock laser to match its color to the transition of the atom we’re using as a clock signal.” The tick for this 3D gas clock is the frequency that prompts the strontium atoms to switch energy levels, which is 430 trillion cycles per second. It’s so precise that it can keep time without losing or gaining a second for 15 billion years.
“Optical atomic clocks are now performing hundreds of times better than microwave clocks. Time is a topic of active discussion. When will be the right time to replace the current cesium clock with the strontium clock or another atom? Defining time is a human endeavor that requires international cooperation and a universal agreement.”
Ye’s pursuit of an ultra-precise atomic clock isn’t just about refining the standard of time. Because atomic clocks measure the interplay between electrons and elementary particles, they are unique tools for investigating the nature of our universe. “We are building more precise and sensitive scientific instruments to detect gravitational waves or the presence of dark matter. If you understand the fabric of space-time, you can measure how dark matter affects it. Time is interconnected with space; as bodies move, merge, and separate, time changes everywhere. If you build clocks with high precision, you will eventually detect the microscopic noise occurring in the universe.”
“I’m optimistic that within the next 30 years, we might reach the point where we can measure the gravitational effects on quantum physics and continue to explore the universe’s limits.”
Quantum – A discrete quantity of energy proportional in magnitude to the frequency of the radiation it represents, fundamental in quantum mechanics. – The quantum nature of light was first proposed by Max Planck and later expanded upon by Albert Einstein.
Clocks – Devices used to measure and indicate time, often based on periodic phenomena such as the oscillations of atoms. – Atomic clocks, which use the oscillations of cesium atoms, are the most accurate timekeeping devices available.
Atoms – The basic units of matter and the defining structure of elements, consisting of a nucleus surrounded by electrons. – In physics, the behavior of atoms is crucial for understanding the principles of quantum mechanics.
Timekeeping – The process or activity of recording the time of events, often using precise instruments. – Advances in timekeeping have allowed scientists to test the effects of relativity with unprecedented accuracy.
Oscillations – Regular variations in magnitude or position around a central point, often used in the context of waves or periodic motion. – The oscillations of a pendulum were historically used in the design of early mechanical clocks.
Precision – The quality of being exact and accurate, often crucial in scientific measurements and experiments. – The precision of modern spectrometers allows for detailed analysis of atomic and molecular structures.
Frequencies – The number of occurrences of a repeating event per unit of time, often measured in hertz (Hz). – The frequencies of electromagnetic waves determine their position in the electromagnetic spectrum.
Gravitational – Relating to the force of attraction between masses, a fundamental interaction in physics. – Gravitational waves, predicted by Einstein’s theory of general relativity, were first observed in 2015.
Measurements – The process of obtaining the magnitude of a quantity relative to a defined standard. – Accurate measurements of cosmic microwave background radiation provide insights into the early universe.
Technology – The application of scientific knowledge for practical purposes, especially in industry and research. – Advances in telescope technology have allowed astronomers to observe distant galaxies in unprecedented detail.
