Unveiling the Universe’s Secrets: MIT Physicist Explores an Alternate Reality of Quantum Boomerangs

MIT physicist Daniel Harlow delves into an alternate quantum reality in his pursuit of unraveling the fundamental mysteries of our physical universe.

Daniel Harlow, a physicist hailing from MIT, devotes significant time to pondering the intricacies of a “boomerang” universe.

His main focus revolves around one of the most profound questions in modern physics: How does our universe adhere to two conflicting sets of laws?

The first set is described by the Standard Model of Physics, a quantum mechanical theory encompassing particles, fields, and forces, which explains the interactions responsible for constructing our observable universe. The second set comprises Einstein’s theory of general relativity, which delineates the influence of gravity and its role in binding matter together to form planets, galaxies, and other celestial bodies.

Both theories excel in their respective domains. However, Einstein’s theory falls short when attempting to explain the behavior of gravity at quantum scales, while quantum mechanics produces mind-boggling predictions when applied to massive cosmic dimensions. For over a century, scientists have tirelessly sought to unite these two theories and uncover the fundamental truths underlying the workings of our universe.

Harlow posits that the key to connecting these divergent theories might be found in a delicate and elusive thread, one that eludes our grasp within our existing universe. Consequently, he explores an alternate version known as the “boomerang” reality. This alternate universe, unlike our continuously expanding universe, loops back onto itself, much like the trajectory of a boomerang. In this “boomerang” universe, quantum gravity becomes more comprehensible and can be reformulated using conventional quantum theory (without gravity), employing a potent concept called holographic duality. As a result, contemplating quantum gravity becomes significantly simpler, at least from a theoretical standpoint.

Within this unique realm, Harlow has made remarkable and unexpected discoveries. He demonstrated that the equations governing gravity in this “toy” universe are identical to the equations controlling quantum error-correcting codes, which have the potential to be employed in the construction of real-world quantum computers. The revelation that the mathematics underpinning gravity might intersect with the safeguarding of information in quantum computers was a surprising revelation in itself. The fact that both phenomena share the same physics, at least within this alternate universe, suggests a potential connection between Einstein’s theory and quantum mechanics within our own reality.

This groundbreaking discovery, made by Harlow during his time as a postdoctoral researcher at Princeton University in 2014, has opened up new avenues of exploration in the fields of quantum gravity and quantum information theory. Since joining MIT and the Center for Theoretical Physics in 2017, Harlow has continued his quest to unveil the fundamental connections between general relativity and quantum mechanics, particularly in the contexts of black holes and cosmology.

Harlow firmly believes that while scientists study diverse systems and conduct various experiments, many underlying concepts and ideas remain universal. Thus, he keeps an open mind, listens attentively, and seeks potential connections among seemingly disparate fields.

“A Humanist Philosophy”

Born in Cincinnati, Harlow moved to Boston with his family as a child and later settled in Chicago. At the age of 10, he embarked on piano lessons, initially focusing on classical music before venturing into the realm of rock. During his junior high years, Harlow played the keyboard in different bands until he found his passion for the improvisational style of jazz.

Harlow’s love for jazz was a driving force that led him to New York City after high school. He enrolled at Columbia University, drawn not only by the vibrant jazz scene but also by the university’s core curriculum, which emphasized the study of classic literary and philosophical works.

At Columbia, Harlow worked as an undergraduate research assistant in an experimental cosmology lab for three years. This experience exposed him to the intricacies of working in a clean room and running simulations to enhance the performance of filters designed to detect faint traces of radiation from the Big Bang.

One aspect that resonated with Harlow during his time at Columbia was the approach of his lab’s leader, Amber Miller, who was then a junior faculty member. Miller’s emphasis on intellectual exploration rather than immediate results or publications left a lasting impression on Harlow.

Open Questions

This mindset of intellectual freedom continued to shape Harlow’s career. After completing his undergraduate studies at Columbia, he journeyed west to Stanford University in 2006. Within Stanford’s physics department, he found his natural alignment with Professor Leonard Susskind, a renowned theoretical physicist specializing in string theory.

Harlow’s shared vision with Susskind, which emphasized identifying the essential aspects of a problem and discarding the rest, solidified his decision to choose Susskind as his advisor. Susskind encouraged Harlow to work on topics of his own choosing and engage in open discussions.

With this invitation to explore, Harlow attentively absorbed conversations within Susskind’s group, gaining insight into the fundamental questions that drove the field. It was during this time that he encountered a problem that would shape his research career: the challenge of merging quantum mechanics with general relativity within the context of cosmology and the understanding of the universe’s large-scale structure and evolution.

To tackle this challenge, Harlow immersed himself in extensive readings on both theories, extending his exploration into the realm of quantum information science. This field focuses on applying principles from quantum mechanics and information theory to the study and development of quantum computers.

Harlow explains that whenever he perceives the importance of a particular tool for solving a problem, he delves deeper into its intricacies. More often than not, this investment pays off in unexpected ways.

Toward the end of his time at Stanford, Harlow decided to embark on a “hard turn,” redirecting his focus from cosmology to black holes. He considered black holes a simpler system to study in the pursuit of understanding the fundamental connections between quantum mechanics and general relativity.

In 2012, he embarked on a postdoctoral position at Princeton University, where he explored the quantum behavior of gravitational black holes. To simplify the problem, he examined this behavior within a “boomerang” universe, also known as “anti-de Sitter space” in physics, named after a physicist who studied the curvature of the universe. While delving deeper into quantum information science, Harlow observed an unexpected and significant overlap between the physics of gravity around black holes and the quantum error-correcting codes designed to preserve information.

This period at Princeton marked a transformative and exploratory phase for Harlow. Many of the paths he embarked on during this time continue to shape his research.

Following a subsequent postdoctoral position at Harvard University, Harlow joined MIT as a junior faculty member in 2017. At MIT, he continues to forge astonishing connections in the realms of quantum gravity and quantum information science. The institute, along with the wider field of theoretical physics, fosters a collegial and productive environment that dismisses authority.

Harlow appreciates the fact that he can approach the most eminent theoretical physicists in the world, challenge their ideas, and be heard if he presents a compelling argument. The community thrives on openness and shares a common goal of seeking the correct answers, regardless of who discovers them.

Among Harlow’s notable accomplishments since joining MIT are stringent constraints on the potential symmetries of quantum gravity, a deeper understanding of energy in gravitational systems, and a concrete mathematical framework for comprehending the interiors of quantum mechanical black holes.

Beyond his research, Harlow actively works to promote diversity and inclusion in the field of physics. In addition to mentoring and advocacy outside of MIT, he has established a program within the physics department that invites students from underrepresented and underprivileged backgrounds to engage in physics research at MIT during the summers.

Unfortunately, the field of physics remains predominantly homogeneous, with a lack of representation from diverse backgrounds. Harlow considers it a priority to make physics more welcoming and accessible to a broader spectrum of humanity.

As Harlow ponders the future, he contemplates a potential shift in his research trajectory. He envisions focusing less on black holes in a holographic universe and devoting more attention to cosmology, exploring the quantum structure and evolution of our own universe.

“I have spent considerable time in anti-de Sitter space,” Harlow reflects. “While that has been valuable, I also aspire to comprehend the world we inhabit. And that should be an enjoyable endeavor.”

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More about Quantum Boomerangs

• MIT News: Quantum Boomerangs
• MIT Center for Theoretical Physics
• Princeton University Physics Department
• Stanford University Department of Physics
• Columbia University Department of Physics
• Harvard University Department of Physics
• MIT Physics Department