Public Lecture Archives

2023

April 11: Donna Strickland

Generating High-Intensity, Ultrashort Optical Pulses

With the invention of lasers, the intensity of a light wave was increased by orders of magnitude over what had been achieved with a light bulb or sunlight. This much higher intensity led to new phenomena being observed, such as violet light coming out when red light went into the material. After Gerald Mourou and I developed chirped pulse amplification, also known as CPA, the intensity again increased by more than a factor of 1,000 and it once again made new types of interactions possible between light and matter. We developed a laser that could deliver short pulses of light that knocked the electrons off their atoms. This new understanding of laser-matter interactions, led to the development of new machining techniques that are used in laser eye surgery or micromachining of glass used in cell phones.

October 12: Adam Riess

The Surprising Expansion History of the Universe

In 1929 Edwin Hubble discovered that our Universe is expanding. Eighty years later, the Space Telescope that bears his name is being used to study an even more surprising phenomenon: that the expansion is speeding up. The origin of this effect is not known, but is broadly attributed to a type of "dark energy" first posited to exist by Albert Einstein and now dominating the mass-energy budget of the Universe. Professor Riess will describe how his team discovered the acceleration of the Universe and why understanding the nature of dark energy presents one of the greatest remaining challenges in astrophysics and cosmology. He will also discuss recent evidence that the Universe continues to defy our best efforts to predict its behavior.

2022

October 5: Lene Hau

The Science and Art of Taming Light [Video]

Nothing goes faster than light... usually!

In our laboratory we have used ultra-cold atom clouds to slow light pulses to the speed of a bicycle, which is 50 million times lower than the light speed in vacuum. In the process, a light pulse spatially compresses by the same large factor, from 1 km to only 0.02 mm, and the pulse can then be completely stopped and later restarted.

From here, we have taken matters further: Stopped and extinguished a light pulse in one part of space and revived it in a completely different location. In the process, the light pulse is converted to a perfect matter copy that can be stored – 'put on the shelf' – sculpted, and then turned back to light. The storage time can be tens of seconds, and during this time, light could – under normal circumstances – travel back and forth to the Moon many times over. The experiments represent the ultimate degree of quantum control over light and matter, and in the talk I will describe how we manipulate light to this extreme.

2019

February 22: Mark Kasevich

Quantum Measurements for Bio-Imaging and Precision Sensing (Video)

Abstract: Innovations in quantum science and technology have enabled previously unforeseen levels of measurement and control over simple quantum systems comprised of atoms, electrons and photons. This talk will illustrate some of these advances with examples relevant to bio-imaging and precision sensing. For example, so-called quantum non-demolition measurements provide a foundation for next generation electron microscopes capable of low-damage imaging of biological samples such as proteins. Related non-demolition protocols for atoms in high finesse optical cavities are used to produce entangled states of more than 1000 ultra-cold atoms. These states are exploited to improve the performance of atomic clocks. Finally, atom de Broglie wave interference experiments with atomic wave packets separated by distances as large as 54 cm (image below is the resulting interference pattern) are being used for new tests of gravity and quantum mechanics. These examples, and their possible impact on basic science and technology, will be discussed.

2018

February 7: Andrzej Dragan

Quantum Theory versus Common Sense (Video)

Abstract: I will show why many of the inventors of quantum theory hated it so much and reveal that the reality we inhabit is as weird as it gets. And there will also be some David Lynch.

May 9: Jerome Friedman

Are We Really Made of Quarks? (Video)

Abstract: The answer to the question, "Are we really made of quarks?", is yes; but physicists did not arrive at this answer easily. The quark model, which embodied a radically new conceptual view of the structure of matter, was fiercely debated and generally rejected by the physics community. Its ultimate acceptance took well over a decade and occurred only after inescapable and compelling experimental evidence, but free quarks have never been observed. This talk will describe how physicists came to this seemingly strange conclusion and discuss the implications of such a picture on our concept of matter.

2016

February 25: Joseph R. Dwyer

Weird Lightning: Sprites, Elves, and Other Strange Things Found in Our Atmosphere

Abstract: Lightning strikes our planet about a billion times per year, killing as many people as hurricanes or tornadoes. Surprisingly, despite its familiarity, we still don’t understand many things about lightning, including how it gets started inside thunderstorms and how it travels such large distances through air. In addition, many new and strange phenomena have been discovered in and around thunderstorms, including colossal jellyfish-like structures near the edge of space called Sprites; enormous, expanding rings of light called Elves; bizarre, bluish jets shooting out of cloud tops; powerful flashes of gamma rays emanating from deep inside storms; and large but nearly invisible discharges called Dark Lightning. In this presentation, I will talk about the mysteries of lightning and other weird things that lightning does.

2015

July 7: John Preskill

Quantum Computing and the Entanglement Frontier (Video)

Abstract:The quantum laws governing atoms and other tiny objects seem to defy common sense, and information encoded in quantum systems has weird properties that baffle our feeble human minds. John Preskill will explain why he loves quantum entanglement, the elusive feature making quantum information fundamentally different from information in the macroscopic world. By exploiting quantum entanglement, quantum computers should be able to solve otherwise intractable problems, with far-reaching applications to cryptology, materials, and fundamental physics science. Preskill is less weird than a quantum computer, and easier to understand.

John Preskill is the Richard P. Feynman Professor of Theoretical Physics at the California Institute of Technology, and Director of the Institute for Quantum Information and Matter at Caltech.

May 19: Chris Impey

Our Future Off-Earth (Video)

Abstract: The Space Age is half a century old. Its early successes were driven by a fierce superpower rivalry between the Soviet Union and the United States, which tended to obscure the fact that exploration and risk-taking is built into human DNA. Decades after we last set foot on the Moon, and several years after the Space Shuttle was retired, the space activity is finally leaving the doldrums. A vibrant private sector led by SpaceX and Virgin Galactic plans to launch supplies cheaply into Earth orbit and give anyone the chance of a sub-orbital joy ride. New materials are being developed that could lead to space elevators and transform the economics of space travel. Fighting gravity will always be difficult but engineers are rethinking rockets and developing new propulsion technologies. Permanent bases on the Moon and Mars are now within reach, and a new space Race is brewing, with the Asian countries ascendant. Medical advances might even allow us to reach for the stars. The talk will review the history and landmarks of the international space program, give a snapshot of the current dynamic situation, and plot the trajectory of the future of space travel. The time has come to envision our future off-Earth.