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MIT Better World

Danna Freedman

By Pamela Ferdinand

Her lab’s groundbreaking work using synthetic chemistry to design novel molecules potentially paves the way for quantum sensing and communication applications to be conducted with a new set of tools—molecule—versus traditionally used, and intrinsically more limiting, solid-state materials.

“I was speechless. This is an incredible honor,” says Freedman, the F. G. Keyes Professor of Chemistry. “It’s acknowledgment that we’re on the right track, that we opened up a door into a real field that has real potential, not just on paper but to impact the world around us.”

Quantum mechanics is a field of physics that seeks to understand the behavior of the tiniest particles in the universe—particles that are small or smaller than atoms (including electrons, protons, and neutrons) and behave differently from larger objects, often in strange ways. The first “quantum revolution” of the 20th century led scientists to observe quantum properties and develop technologies like lasers, the transistor, GPS, magnetic resonance imaging, and semiconductors. Now, in the second quantum revolution, scientists like Freedman are seeking to harness those properties and apply them to a wide range of fields.

At the heart of this work, and one of its biggest hurdles, is the concept of electron spin, a quantum property and form of angular momentum that influences the position of electrons and nuclei in atoms and molecules. Spin can have two states but also a natural third state that’s a combination of the two, called superposition. (Think about something on Earth existing not just in one position like up or down but in several positions all at once, or a spinning coin that is neither heads nor tails.)

Few molecules remain in this third state long enough to measure, so they have been difficult to use as building blocks for quantum technologies. Freedman, a former MIT postdoc who joined the faculty in 2021, appears to have devised a way using a bottom-up approach.

From the electron spin of certain molecules, her lab has created a new class of quantum units, or qubits, that retain superposition and can be manipulated to control quantum system properties. Their research has shown that qubits—in this case, molecules designed with a central chromium atom surrounded by four hydrocarbon molecules—could be customized for specific targets within quantum sensing and communication.

Using chemical control, Freedman says spins can be positioned in chosen orientations or separated by form (electron versus proton). Specific combinations of atoms can even be forced to interact to shed light on the nature of a chemical bond. “Chemistry enables us to make systems that are atomically precise, reproducible, and tunable,” she says.

Next-generation information processing

Freedman is reluctant to speculate about the potential real-world applications of her research, but a next generation of molecular components could perform otherwise impossible information-processing (sensing, communication, and measurement) tasks with an unprecedented level of specification and accuracy.

“Molecules are uniquely suited for a lot of quantum sensing applications and for quantum communication applications,” Freedman says. “You can use a molecule to put atoms exactly where you want them to be and then tune them so you can get a whole array of properties, and that combination is incredibly powerful for applications where specificity is important.”

One direction she hopes to pursue with her MacArthur grant is working with other scientists on quantum sensors, which are extremely sensitive to minuscule variations in their environment. Freedman’s lab also works on targeting emergent properties and applying extreme pressure to synthesize new materials, which could impact areas such as energy generation and transport.

Creativity and scholarly depth

Freedman’s deep passion for her work is palpable. In high school, she taught science to 11-year-olds and worked at the local observatory running the telescope and conducting tours. That’s where she heard a guest scientist explain an alternative theory to dark matter. Now, decades later, she’s thrilled to also be collaborating on a dark matter detection project.

“I’ve been hearing about this since I was 15,” she says. “How lucky am I that I had such a long exposure.”

Freedman describes MIT as “phenomenally interdisciplinary.” Her office is near that of Peter Shor PhD ’85, the renowned mathematician and quantum computing pioneer. “This is just an inspirational place to be,” Freedman says. “There’s a lot of creativity, risk taking, and ambition, but it’s also met by a scholarly depth, which is essential.”