Notícias

Dec 01, 2023

Compressão Quântica: No Limite da Física

Por Whitney Clavin, Instituto de Tecnologia da Califórnia (Caltech)30 de julho de 2023 Lee McCuller, professor de física e especialista em compressão quântica, está desenvolvendo técnicas inovadoras para aprimorar o

Por Whitney Clavin, Instituto de Tecnologia da Califórnia (Caltech)30 de julho de 2023

Lee McCuller, professor de física e especialista em compressão quântica, está desenvolvendo técnicas inovadoras para aumentar a sensibilidade do LIGO, o detector de ondas gravitacionais mais avançado do mundo. A sua ambição futura é ampliar a aplicação destas técnicas para além do LIGO.

O novo professor da Caltech, Lee McCuller, está tornando as medições quânticas ainda mais precisas.

Desde muito jovem, o novo professor assistente de Física, Lee McCuller, gostava do processo prático de construir coisas. Esse interesse foi estimulado por seu tio, que criou uma fonte de alimentação para ele. McCuller usou isso em conjunto com kits eletrônicos de hobby da RadioShack, realizando tarefas simples, como operar circuitos analógicos para ligar e desligar luzes e motores. Hoje, as proezas de engenharia de McCuller são aplicadas a um dispositivo excepcionalmente avançado, que alguns chamariam de o dispositivo de medição mais avançado do mundo: o Observatório de Ondas Gravitacionais com Interferômetro Laser, ou LIGO.

Lee McCuller, professor assistente de física. Crédito: Caltech

McCuller is a recognized expert in a field known as quantum squeezing, a technique utilized at LIGOThe Laser Interferometer Gravitational-Wave Observatory (LIGO) is a large-scale physics experiment and observatory supported by the National Science Foundation and operated by Caltech and MIT. It's designed to detect cosmic gravitational waves and to develop gravitational-wave observations as an astronomical tool. It's multi-kilometer-scale gravitational wave detectors use laser interferometry to measure the minute ripples in space-time caused by passing gravitational waves. It consists of two widely separated interferometers within the United States—one in Hanford, Washington and the other in Livingston, Louisiana." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">LIGO to achieve extremely 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 wavesGravitational waves are distortions or ripples in the fabric of space and time. They were first detected in 2015 by the Advanced LIGO detectors and are produced by catastrophic events such as colliding black holes, supernovae, or merging neutron stars." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"> ondas gravitacionais. Os detectores do LIGO – localizados em Washington e Louisiana – são especializados em captar essas ondas, mas são limitados pelo ruído quântico, uma propriedade inerente da mecânica quântica que resulta na entrada e saída de fótons no espaço vazio. A compressão quântica é um método complexo para reduzir esse ruído indesejado.

A pesquisa sobre compressão quântica e medições relacionadas aumentou já na década de 1980, com estudos teóricos importantes de Kip Thorne da Caltech (BS '62), Richard P. Feynman Professor de Física Teórica, Emérito, junto com o físico Carl Caves (PhD '79 ) e outros em todo o mundo. Essas teorias inspiraram a primeira demonstração experimental de compressão em 1986 por Jeff Kimble, professor emérito de física William L. Valentine. As décadas seguintes viram muitos outros avanços na investigação e agora McCuller está na vanguarda deste campo inovador. Por exemplo, ele tem estado ocupado desenvolvendo a compressão “dependente de frequência” que aumentará muito a sensibilidade do LIGO quando ele for ligado novamente em maio deste ano.

After earning his bachelor’s degree from the University of Texas at Austin in 2010, McCuller attended the University of ChicagoFounded in 1890, the University of Chicago (UChicago, U of C, or Chicago) is a private research university in Chicago, Illinois. Located on a 217-acre campus in Chicago's Hyde Park neighborhood, near Lake Michigan, the school holds top-ten positions in various national and international rankings. UChicago is also well known for its professional schools: Pritzker School of Medicine, Booth School of Business, Law School, School of Social Service Administration, Harris School of Public Policy Studies, Divinity School and the Graham School of Continuing Liberal and Professional Studies, and Pritzker School of Molecular Engineering." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]">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 MITMIT is an acronym for the Massachusetts Institute of Technology. It is a prestigious private research university in Cambridge, Massachusetts that was founded in 1861. It is organized into five Schools: architecture and planning; engineering; humanities, arts, and social sciences; management; and science. MIT's impact includes many scientific breakthroughs and technological advances. Their stated goal is to make a better world through education, research, and innovation." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"MIT’s Rai Weiss—who 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./p>

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 frequencies—which occur earlier in, say, a black holeA black hole is a place in space where the gravitational field is so strong that not even light can escape it. Astronomers classify black holes into three categories by size: miniature, stellar, and supermassive black holes. Miniature black holes could have a mass smaller than our Sun and supermassive black holes could have a mass equivalent to billions of our Sun." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"black hole merger, before the bodies collide—we 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./p>

What this means is that we will be even more sensitive to the early phases of black hole and neutron starA neutron star is the collapsed core of a large (between 10 and 29 solar masses) star. Neutron stars are the smallest and densest stars known to exist. Though neutron stars typically have a radius on the order of just 10 - 20 kilometers (6 - 12 miles), they can have masses of about 1.3 - 2.5 that of the Sun." data-gt-translate-attributes="[{"attribute":"data-cmtooltip", "format":"html"}]"neutron star mergers, and that we can see even fainter mergers./p>