Life in a hologram » MIT Physics

Physicist Daniel Harlow explores an alternate quantum actuality in quest of basic truths to our bodily universe.

Dan Harlow spends a variety of time considering in a “boomerang” universe.

The MIT physicist is trying to find solutions to one of many largest questions in fashionable physics: How can our universe abide by two incompatible rulebooks?

The primary — the Customary Mannequin of Physics — is the quantum mechanical concept of particles, fields, and forces, and the methods through which they work together to construct the universe we stay in. The second — Einstein’s concept of basic relativity — describes the affect of gravity and the way the basic pressure pulls collectively matter to construct the planets, galaxies, and different huge objects.

Each theories do remarkably effectively of their respective lanes. Nevertheless, Einstein’s concept breaks down when attempting to explain how gravity works at quantum scales, whereas quantum mechanics makes reality-bending predictions when utilized at huge, cosmic dimensions. For over a century, physicists have searched for tactics to unite the 2 theories and get to the reality of what makes our universe tick.

Harlow suspects that any connecting thread could also be too delicate to understand in our current universe. As an alternative, he’s searching for solutions in a “boomerang” model — an alternate actuality that folds again on itself, very like a boomerang’s trajectory, moderately than stretching and increasing with out finish as our precise universe does. Quantum gravity on this boomerang universe seems to be simpler to know, as it may be reformulated by way of typical quantum concept (with out gravity) utilizing a strong concept referred to as holographic duality. This makes it far less complicated to ponder, not less than from a concept perspective.

On this boomerang atmosphere, Harlow has made some thrilling, sudden revelations. He has proven, as an illustration, that the equations that describe how gravity behaves on this “toy” universe are the exact same equations that management the quantum error-correcting codes that may hopefully quickly be used to construct real-world quantum computer systems. That the arithmetic describing gravity ought to have something to do with defending info in quantum computer systems was a shock in itself. The truth that each phenomena shared the identical physics, not less than on this alternate universe, suggests a possible connection between Einstein’s concept and quantum mechanics in the actual universe.

The invention, which Harlow made as a postdoc at Princeton College in 2014, sparked contemporary strains of inquiry within the examine of each quantum gravity and quantum info concept. Since becoming a member of MIT and the Middle for Theoretical Physics in 2017, Harlow has continued his seek for basic connections between basic relativity and quantum mechanics, and the way they might intersect within the contexts of black holes and cosmology.

“One of many issues that’s been enjoyable is, despite the fact that in physics and extra in usually science we’re all finding out completely different techniques and experiments, lots of the concepts are the identical,” says Harlow, an affiliate professor who acquired tenure in 2022. “So, I attempt to have an open thoughts and preserve my ears open, and search for how issues could also be associated.”

“A humanist philosophy”

Born in Cincinnati, Harlow moved as a toddler together with his household to Boston, the place he spent a number of years earlier than the household moved once more, placing down roots in Chicago. When he was 10, he took up piano classes, focusing first on classical music, then rock. In junior excessive, he performed keyboard in numerous bands earlier than discovering his groove within the looser, extra improvisational model of jazz.

“I like sitting down and taking part in with individuals, and seeing the place issues will go,” Harlow says.

His love of jazz was partly what drew him to New York Metropolis after highschool, the place he attended Columbia College, which occurred to be close to among the greatest jazz golf equipment within the metropolis. The college’s core curriculum, which required college students to learn basic works of literature and philosophy, additionally appealed.

“You’ll be able to’t graduate from Columbia with out studying “The Iliad,” Harlow says. “That offers you a shared neighborhood of issues you’ll be able to discuss. I preferred the humanist philosophy that drives the place. Even when I selected to be a physicist, I’d nonetheless have this broader cultural expertise.”

Harlow labored for 3 years as an undergraduate analysis assistant in an experimental cosmology lab on campus, the place he realized to work in a clear room and run simulations to enhance the efficiency of filters that have been designed to select refined indicators of radiation left over from the Large Bang.

Harlow notably appreciated the overall method of the lab’s chief, Amber Miller, who was then a junior college member.

“She had this good way she ran her group, the place she wasn’t so hung up on publications or getting issues achieved on a brief timescale,” Harlow recollects. “She simply allow us to mess around.”

Open questions

That psychological freedom to discover new concepts would stick with Harlow all through his profession. From Columbia, he went west to Stanford College in 2006. Throughout the physics division, he discovered he aligned most naturally with Professor Leonard Susskind, a theoretical physicist and chief within the examine of string concept.

“His sturdy want to determine the issues that aren’t essential and set them apart so you’ll be able to concentrate on the essence of the issue — that was additionally the way in which I attempt to assume,” says Harlow, who ended up selecting Susskind as his advisor. “Lenny stated, ‘work on no matter you need, and I’ll speak to you about it.’”

With this open invitation, Harlow saved an ear on conversations inside Susskind’s group to get a way of the massive questions within the discipline. What he heard was an issue that might form the remainder of his analysis profession: the query of learn how to join quantum mechanics with basic relativity, within the context of cosmology, and scientists’ understanding of the large-scale construction and evolution of the universe.

Looking for a solution, Harlow learn up on every little thing he might discover on each theories. His studying additionally bled into quantum info science — primarily, a discipline that focuses on making use of rules of quantum mechanics and knowledge concept to the examine and growth of quantum computer systems.  

“Every time I’ve a touch that some software might be essential for an issue I’m attempting to unravel, I be taught way more about it than what I believe I want,” Harlow says. “Most of the time, that funding pays off.”

On the finish of his time at Stanford, Harlow determined to “take a tough flip,” pivoting from cosmology to black holes, which he thought-about to be an easier system to check for any basic threads connecting quantum mechanics and basic relativity.

In 2012, he went again east to Princeton for a three-year postdoc, throughout which he started to discover the quantum habits of gravitational black holes. To simplify the issue, he did so in a “boomerang” universe — what physicists know as “anti-de Sitter area,” named after the physicist who studied the curvature of the universe. As Harlow learn extra on quantum info, he observed, and finally confirmed, an sudden overlap within the physics of gravity round black holes and the quantum error-correcting codes designed to guard info.

“That was a really exploratory, transformative time,” Harlow says. “I’m nonetheless exploring a variety of the paths that I began there.”

After a second postdoc at Harvard College, Harlow joined MIT as a junior college member in 2017, the place he continues to make shocking connections within the examine of quantum gravity and quantum info science. On the Institute, and within the discipline of theoretical physics extra broadly, he’s loved a collegial, productive disregard for authority.

“It is a neighborhood the place I can go as much as probably the most well-known theoretical physicist on the planet, inform them that they’re mistaken, and if I’ve an argument, they’ll hearken to me,” Harlow says. “Persons are open. There’s this core shared settlement that, what issues is that we discover the suitable reply. It issues much less who finds it.”

Amongst Harlow’s accomplishments since coming to MIT are a proof that there are sturdy restrictions on the potential symmetries of quantum gravity, a deeper understanding of the character of vitality in gravitational techniques, and a concrete mathematical framework for understanding the interiors of quantum mechanical black holes.

Past analysis, Harlow is working to deliver extra numerous voices and views into the sphere of physics. Along with mentoring and advocacy work outdoors of MIT, he’s working a program inside the physics division that invitations college students from underrepresented and underprivileged backgrounds to hold out physics analysis at MIT every summer season.

“Sadly physics stays moderately white and male, and making it extra welcoming and accessible to a broader slice of humanity is considered one of my priorities going ahead,” he says.

Wanting forward, Harlow is contemplating taking a brand new flip in his analysis path, maybe to focus much less on black holes in a hologram universe, and extra on cosmology, and the quantum construction and evolution of our precise universe.

“I’ve been dwelling in anti-de Sitter area for a very long time,” Harlow says. “That’s superb, however I do wish to perceive the world we stay in too. And that ought to be enjoyable.”