When new assistant professor of physics Lee McCuller was young, he liked to build things. His uncle made him a power supply, which he integrated with electronic hobby kits from RadioShack to do simple things like use analog circuits to switch lights and motors on and off. Today, McCuller tinkers with what some would call the most advanced measurement device in the world: LIGO, or the Laser Interferometer Gravitational-wave Observatory.
McCuller is an expert on quantum squeezing, a method used at LIGO to make incredibly precise measurements of gravitational waves that travel millions and billions of light-years across space to reach us. When black holes and collapsed stars, called neutron stars, collide, they generate ripples in space-time, or gravitational waves. LIGO's detectorslocated in Washington and Louisianaspecialize in picking up these waves but are limited by quantum noise, an inherent property of quantum mechanics that results in photons popping in and out of existence in empty space. Quantum squeezing is a complex method for reducing this unwanted noise.
Research into quantum squeezing and related measurements ramped up as far back as the 1980s, with key theorical studies by Caltech's Kip Thorne (BS '62), Richard P. Feynman Professor of Theoretical Physics, Emeritus, along with physicist Carl Caves (PhD '79) and others worldwide. Those theories inspired the first experimental demonstration of squeezing in 1986 by Jeff Kimble, the William L. Valentine Professor of Physics, Emeritus. The next decades saw many other advances in squeezing research, and now McCuller is at the leading edge of this innovative field. For example, he has been busy developing "frequency-dependent" squeezing that will greatly enhance LIGO's sensitivity when it turns back on in May of this year.
After earning his bachelor's degree from the University of Texas at Austin in 2010, McCuller attended the University of Chicago, where he earned his PhD in physics in 2015. There he began work on an experiment called the Fermilab Holometer, which looked for a speculative type of noise that would link gravity with quantum mechanics. It was during this project that McCuller met LIGO scientists, including MIT's Rai Weisswho together with Thorne and Barry Barish, the Ronald and Maxine Linde Professor of Physics, Emeritus, won the Nobel Prize in Physics in 2017 for their groundbreaking work on LIGO. McCuller was inspired by Weiss and the LIGO project and decided to join MIT in 2016. He became an assistant professor at Caltech in 2022.
In the future, McCuller hopes to take the quantum measurement tools he has developed for LIGO and apply them to other problems. "If LIGO is the most precise ruler in the world, then we want to make those rulers available to everyone," he says.
We met with McCuller over Zoom to learn more about quantum squeezing and its future applications to other fields as well as what inspired McCuller to join Caltech.
After I graduated from University of Chicago in 2015, I went to work on LIGO at MIT. When I walked in the door, they were having a meeting about the first detection of gravitational waves! The public didn't know yet, but there had been rumors. It was exciting to learn the rumors were true, and it was nice to see everyone overjoyed that things were working.
There was a local experiment taking place at that time on using squeezed light in the frequency-dependent manner that will start up at LIGO later this year. My job was to help build the first full-scale demonstration of this. The group, before me, had previously demonstrated the concept but not at the full scale. I was there was to show exactly what would be needed to employ it in the LIGO observatories. This required a particularly challenging experimental setup.
At each of the observatory locations, LIGO uses laser beams to measure disturbances in space-timethe gravitational waves. The laser beams are shot out at 90-degrees from each other and travel down two 4-kilometer-long arms. They reflect off mirrors and travel back down the arms to meet back up. If a gravitational wave passes through space, it will stretch and squeeze LIGO arms such that the lasers will be pushed out of sync; when they meet back up, the combined laser will create an interference pattern.
At the quantum level, there are photons in the laser light that hit the mirrors at different times. We call this shot noise, or quantum noise. Imagine dumping out a can full of BBs. They all hit the ground and click and clack independently. The BBs are randomly hitting the ground, and that creates a noise. The photons are like the BBs and hit LIGO's mirrors at irregular times. Quantum squeezing, in essence, makes the photons arrive more regularly as if the photons are holding hands rather than traveling independently. And this means that you can more precisely measure the phase or frequency of the light inside LIGOand ultimately detect even fainter gravitational waves.
To squeeze light, we are basically pushing the uncertainty inherent in light waves from one feature to another. We are making the light more certain in its phase, or frequency, and less certain in its amplitude, or power [the uncertainty principle says that both the exact frequency and amplitude of a light wave cannot be known at the same time]. To really explain the details of how squeezing actually works is very hard! I primarily know how to use math to describe it.
An interesting thing about squeezed light is that we aren't doing anything to the actual laser. We don't even touch it. When we operate LIGO, we offset the arms so that its wave interference is not perfectly darka small amount of light gets through. The little bit of light that remains has an electrical field that interferes with quantum fluctuations in the vacuum, or empty space, and this leads to the shot noise or the photons acting like BBs as we talked about earlier. When we squeeze light, we are actually squeezing the vacuum so that the photons have lower uncertainty in their frequency.
Up until now, we have been squeezing light in LIGO to reduce uncertainty in the frequency. This allows us to be more sensitive to the high-frequency gravitational waves within LIGO's range. But if we want to detect lower frequencieswhich occur earlier in, say, a black hole merger, before the bodies collidewe need to do the opposite: we want to make the light's amplitude, or power, more certain and the frequency less certain. At the lower frequencies, the shot noise, our BB-like photons, push the mirrors around in different ways. We want to reduce that. Our new frequency-dependent cavity at the LIGO detectors is designed to reduce the frequency uncertainty in the high frequencies and the amplitude uncertainties in the low frequencies. The goal is to win everywhere and reduce the unwanted mirror motions.
Part of the reason this technology is more important in the next run is because we are turning up the power on our lasers. With more power, you get more pressure on the mirrors. Our new squeezing technology will allow us to turn the power up without creating the unwanted mirror motions.
What this means is that we will be even more sensitive to the early phases of black hole and neutron star mergers, and that we can see even fainter mergers.
One project I'm working on involves Kathryn Zurek and Rana Adhikari. We are building a tabletop-size detector that will attempt to pick up signatures of quantum gravity, or pixels in space and time as some people say. The idea there is to make interferometers more like high-energy-physics detectors. The detectors would click when something passes through it, largely circumventing the impacts of shot noise. I love the motivation of the projectquantum gravity, which is the quest to merge theories of gravity with quantum physics. It is a very lofty goal.
In general, what I hope to do is grow from the LIGO work and apply quantum measurement techniques to not only enhance the gravitational wave detectors but also to see where other fundamental physics experiments or technologies can be improved. I want to use quantum optics not necessarily for computation or for information but for measurement. Squeezing light is one of the first demonstrations of these concepts in a real experiment. The hope is that we can keep using these quantum techniques in more and more experiments. We want to take the advantages of LIGO and find all the places where we can apply them.
Caltech has a lot of mission-oriented scientists. It's not just about learning or demonstrating or exploringit's the mix of all these things. I like a place where the goal is to integrate technologies and do new experiments. Take LIGO for instance. Few people know how the whole thing works and many of them are here. Caltech is a place where people understand that what we are doing is hard. Good projects require both narrow and broad expertise, and a combination of the right people. The students are similarly motivated by both the science goals and the process. We are not just trying to build something that reliably works, we are also trying to build something that's at the edge of what is possible.
Excerpt from:
At the Edge of Physics - Caltech
- Netflixs 3 Body Problem: The science explained by an astrophysicist - Vox.com - March 24th, 2024 [March 24th, 2024]
- Entanglement entropies of nuclear systems gro - EurekAlert - March 24th, 2024 [March 24th, 2024]
- The Quest for a Theory of Everything Scientists Put Einstein to the Test - SciTechDaily - March 24th, 2024 [March 24th, 2024]
- Vibrating atoms are seen 'tuning' the energy of a single electron - Earth.com - March 24th, 2024 [March 24th, 2024]
- Innovator Spotlight: Joseph Maciejko | The Quad - University of Alberta - March 24th, 2024 [March 24th, 2024]
- A Breakthrough in the Control of Quantum Phenomena at Room Temperature Has Been Achieved, Researchers Say - The Debrief - February 16th, 2024 [February 16th, 2024]
- The End of the Quantum Ice Age: Room Temperature Breakthrough - SciTechDaily - February 16th, 2024 [February 16th, 2024]
- Quantum computer outperformed by new traditional computing - Earth.com - February 16th, 2024 [February 16th, 2024]
- URI program to help STEM professionals pivot into quantum information science careers - The University of Rhode Island - February 16th, 2024 [February 16th, 2024]
- Quantum realm controlled at room temperature for the first time - Earth.com - February 16th, 2024 [February 16th, 2024]
- Quantum Breakthrough: New Method Preserves Information Against All Odds - SciTechDaily - February 16th, 2024 [February 16th, 2024]
- Quantum computers get new design that makes them more "useful" - Earth.com - February 16th, 2024 [February 16th, 2024]
- Beyond Classical Physics: Scientists Discover New State of Matter With Chiral Properties - SciTechDaily - February 16th, 2024 [February 16th, 2024]
- Quantum research sheds light on the mystery of high-temperature superconductivity - Tech Explorist - February 16th, 2024 [February 16th, 2024]
- Unlocking the Mysteries of Quantum Many-Body Systems: A Look at Quantum Simulators and Universal Scaling ... - Medriva - February 16th, 2024 [February 16th, 2024]
- Functioning quantum internet makes giant stride closer to reality - Earth.com - February 13th, 2024 [February 13th, 2024]
- Exploring New Futures in Space: A Revolutionary Integration of Neuroscience, Quantum Physics, and Space Exploration - SETI Institute - February 13th, 2024 [February 13th, 2024]
- Uncovering the Quantum Plateau: Significance and Implications | Nature Physics - Medriva - February 13th, 2024 [February 13th, 2024]
- The State of the Art in Quantum Computing - Medium - February 13th, 2024 [February 13th, 2024]
- Beyond the Visible Universe: New Research Reveals How Gravity Influences the Quantum Realm - SciTechDaily - February 13th, 2024 [February 13th, 2024]
- Leader of IBM's Quantum Safe Team to speak at URI - University of Rhode Island - September 23rd, 2023 [September 23rd, 2023]
- University Assistant Predoctoral, Physics job with UNIVERSITY OF ... - Times Higher Education - September 23rd, 2023 [September 23rd, 2023]
- Zentropy A New Theory That Could Transform Material Science - SciTechDaily - September 23rd, 2023 [September 23rd, 2023]
- Researchers Studying the Quantum Realm Observe Alice in ... - The Debrief - September 23rd, 2023 [September 23rd, 2023]
- Augusta University graduate starts business in the artificial ... - Jagwire Augusta - September 23rd, 2023 [September 23rd, 2023]
- Quantum Echoes: A Revolutionary Method to Store Information as Sound Waves - SciTechDaily - August 14th, 2023 [August 14th, 2023]
- 'Quantum superchemistry' observed for the 1st time ever - Space.com - August 14th, 2023 [August 14th, 2023]
- Quantum Avalanche A Phenomenon That May Revolutionize Microelectronics and Supercomputing - SciTechDaily - August 14th, 2023 [August 14th, 2023]
- Applications of quantum mechanics at the beach - Symmetry magazine - August 14th, 2023 [August 14th, 2023]
- Book Review: On the Origin of Time Stephen Hawking's Final Theory - Moose Jaw Today - August 14th, 2023 [August 14th, 2023]
- Harnessing Quantum Technologies: The Next Big Leap in Global ... - Fagen wasanni - August 14th, 2023 [August 14th, 2023]
- The quantum avalanche - At the Vienna University of Technology, it ... - Chemie.de - August 14th, 2023 [August 14th, 2023]
- Semiconductors: The Linchpin of AI in Quantum Computing - Fagen wasanni - August 14th, 2023 [August 14th, 2023]
- The Promising Collaboration Between AI and Quantum Computing - Fagen wasanni - August 14th, 2023 [August 14th, 2023]
- String theory physicist changed quantum field theory - USC Dornsife College of Letters, Arts and Sciences - August 14th, 2023 [August 14th, 2023]
- QUANTUM SUPERCOMPUTERS. The words Quantum and ... - Medium - August 14th, 2023 [August 14th, 2023]
- Fourteen MIT School of Science professors receive tenure for 2022 ... - MIT News - August 14th, 2023 [August 14th, 2023]
- The Fascinating World of Quantum Integrated Circuits: The Next Big ... - Fagen wasanni - August 14th, 2023 [August 14th, 2023]
- Conclusive Evidence for Modified Gravity: Collapse of Newton's and ... - SciTechDaily - August 14th, 2023 [August 14th, 2023]
- Physicists Open New Path to an Exotic Form of Superconductivity - SciTechDaily - August 14th, 2023 [August 14th, 2023]
- The Principle of Least Action Now Exists in the Quantum Realm - Popular Mechanics - June 10th, 2023 [June 10th, 2023]
- Quantum materials: Electron spin measured for the first time - EurekAlert - June 10th, 2023 [June 10th, 2023]
- Life in a hologram | MIT News | Massachusetts Institute of Technology - MIT News - June 10th, 2023 [June 10th, 2023]
- If Black Holes Evaporate, Everything Evaporates - Universe Today - June 10th, 2023 [June 10th, 2023]
- Clever Ant-Man Easter Egg Links The Movie to the Real World's ... - Startefacts - June 10th, 2023 [June 10th, 2023]
- Quantum Cryptography: The Cutting Edge of Secure Communication - CityLife - June 10th, 2023 [June 10th, 2023]
- This 17-year-old works to make quantum mainstream - Indiatimes.com - June 10th, 2023 [June 10th, 2023]
- The multiverse is doomed and even Spider-Man and The Flash can't save it - Yahoo Entertainment - June 10th, 2023 [June 10th, 2023]
- Physics of Time Travel: A Scientific Perspective - Mirage News - June 10th, 2023 [June 10th, 2023]
- Quantum Spin Liquids: The Future of Superconductors - EnergyPortal.eu - June 10th, 2023 [June 10th, 2023]
- Interview: Three Books That Make Tess Gunty Angry - The New York Times - June 10th, 2023 [June 10th, 2023]
- Events Calendar School of Mathematics and Statistics Colloquium ... - Carleton University - June 10th, 2023 [June 10th, 2023]
- Graphene and Quantum Computing: A Match Made in Heaven - CityLife - June 10th, 2023 [June 10th, 2023]
- A Quantum Computer Simulation Has Reversed Time And Physics May Never Be The Same - Twisted Sifter - June 2nd, 2023 [June 2nd, 2023]
- Realizing the Einstein-Podolsky-Rosen Paradox for Atomic Clouds - Physics - June 2nd, 2023 [June 2nd, 2023]
- The US and UK team up to advance quantum information science - Fermi National Accelerator Laboratory - June 2nd, 2023 [June 2nd, 2023]
- How plants can perform feats of quantum mechanics - Big Think - June 2nd, 2023 [June 2nd, 2023]
- Physicists Make Matter out of Light to Find Quantum Singularities - Scientific American - June 2nd, 2023 [June 2nd, 2023]
- Eventually everything will evaporate, not only black holes - Science Daily - June 2nd, 2023 [June 2nd, 2023]
- Julius-Maximillians-Universitt Wrzburg Researchers Use ... - HPCwire - June 2nd, 2023 [June 2nd, 2023]
- TNTs The Lazarus Project Uses Suspense Trapping to Ask Smart ... - Roger Ebert - June 2nd, 2023 [June 2nd, 2023]
- Quantum Exponential: building a cutting edge quantum technology ... - The Armchair Trader - June 2nd, 2023 [June 2nd, 2023]
- IMDEA Software and IMDEA Networks work to deploy in the ... - EurekAlert - June 2nd, 2023 [June 2nd, 2023]
- Ian Hacking, Eminent Philosopher of Science and Much Else, Dies ... - The New York Times - June 2nd, 2023 [June 2nd, 2023]
- Does mass increase when nearing the speed of light? - Big Think - June 2nd, 2023 [June 2nd, 2023]
- Answering Questions about Boring Numbers, Disasters, Fusion, and ... - Scientific American - June 2nd, 2023 [June 2nd, 2023]
- Spiderman: Across the Spider-verse | Reel World | timesnewspapers ... - Webster-Kirkwood Times, Inc. - June 2nd, 2023 [June 2nd, 2023]
- There's a Secret Way to Get to Absolute Zero. Scientists Just Found It. - Popular Mechanics - May 6th, 2023 [May 6th, 2023]
- Photon Precision: How Quantum Physicists Shattered the Bounds of Sensitivity - SciTechDaily - May 6th, 2023 [May 6th, 2023]
- Do we live in a hologram? Why physics is still mesmerised by this idea - New Scientist - May 6th, 2023 [May 6th, 2023]
- Is Ultimate Truth an Equation? Nah. The Stute - The Stute - May 6th, 2023 [May 6th, 2023]
- UChicago Lab Creates 'Quantum Casino,' a Win-Win to Educate and ... - Polsky Center for Entrepreneurship and Innovation - May 6th, 2023 [May 6th, 2023]
- Physics - Tweezers in Three Dimensions - Physics - May 6th, 2023 [May 6th, 2023]
- Brave new world: On the edge of a second quantum revolution - University of Cape Town News - May 6th, 2023 [May 6th, 2023]
- Researchers pull back the quantum curtain on 'Weyl fermions' - Phys.org - May 6th, 2023 [May 6th, 2023]
- Scale separation: Breaking down unsolvable problems into solvable ones - Phys.org - May 6th, 2023 [May 6th, 2023]
- Postdoctoral Research Associate in Quantum Optics job with ... - Times Higher Education - May 6th, 2023 [May 6th, 2023]
- Australia's first quantum strategy predicts $6 billion in revenue and ... - SmartCompany - May 6th, 2023 [May 6th, 2023]
- Nature's Quantum Secret: Link Discovered Between Photosynthesis ... - SciTechDaily - May 6th, 2023 [May 6th, 2023]
- Two ERC proof of concept grants for the University of Bonn - EurekAlert - May 6th, 2023 [May 6th, 2023]