Stewart Smith
Beneath Green Hero 1b

Beneath the Green,
the Quantum

My year-long Yale Quantum Institute artist residency culminated in a site-specific art installation on the New Haven Green that engaged visitors through its forest of interactive light beacons and the deployment of Yale University’s latest quantum error correction research.

I designed a human-scaled light installation, in collaboration with Yale Quantum Institute researchers and students, that investigates the latest in quantum error correction research—an essential tool in the pursuit of fault-tolerant quantum computing. Visitors are invited to circulate through this interactive forest of vertical illuminated beacons; their bodies acting as proxies for the destructive quantum noise and decoherence that arises within a quantum device as it operates. In response, the illuminated beacons recognize these “quantum errors” and attempt to mitigate them in real-time, illustrated through patterns of light that ripple across the collective. This attempt to resolve observer-induced “error” is driven by actual quantum error correcting algorithms researched and developed at Yale University.

“Beneath the Green, the Quantum” on display in the The New Haven Green during the International Festival of Arts & Ideas.

The New Haven Green occupies the heart of New Haven’s original nine-square city plan. It contains thousands of unmarked graves that lurk just beneath the footfalls of unsuspecting pedestrians.

The crowning lights atop each beacon gently allude to the New Haven Green’s spooky history as a temporary respite for souls en route to a rapturous beyond; metaphorically drawing energy from beneath the grassy surface and transmitting it heavenward—like a photon traversing an impossible barrier in the cold, dark, and isolated environment of a quantum device’s dilution refrigeration tank. And just as the “beach hides beneath the paving stones”, perhaps a united future of students and workers can grow from this soil of uncertainty, seeded by the momentum of generative artificial intelligence and new forms of computation that promise to redefine what it is to labor, produce, and consume.

We invite you to traverse our small forest of light, weaving your own path of human error—as we all do—through the spaces between. And don’t fret. Our algorithms can tidy up.


  • Artist: Stewart Smith. Your humble narrator.
  • Producer: Florian Carle, Ph.D. YQI Institute Manager, Benjamin Franklin College Fellow, creator and producer of the YQI Artist in Residence program.
  • Scientific Consultant: Yue Wu. Yale University computer science Ph.D. student, quantum error correction expert, and hacker extraordinaire.
  • Hardware: Alpay Kasal: Artist and founder of experiential design company Bignoodle in San Francisco.

Quantum Error Correction

Quantum computers store information as data in the form of quantum bits, also known as “qubits.” These qubits are notoriously finicky and susceptible to a type of error known as decoherence. Researchers aim to compensate for these errors with additional, “stabilizer” qubits that are interspersed between the “data” qubits. Earlier this year, Yale researchers were able to use their latest error correction techniques to more than double the lifetime of a qubit—proving that quantum error correction is indeed a practical tool for building ever more reliable quantum computers.

“Beneath the Green” uses the above error correction schema; the illuminated beacons acting as the stabilizer qubits, and the roaming visitors imparting “error” into the system as they walk through data qubit locations (tripping proximity sensors attached to each beacon). Our browser-based simulation of the grid listens for updates from the proximity sensors, communicates these “error” locations to our quantum error correction software, and then orchestrates beacon hues and animations based on the necessary quantum corrective actions. The artwork allows the audience of spectators to become active participants; the act of observation affecting that which is observed. The warm white glow of each unassuming beacon may suddenly pop to a vibrant red as it identifies error. Then, following a series of corrective steps, these mitigated errors yield soft blues. After a beat, the cycle begins again.

A modular forest of light

The form of our illuminated beacons was heavily inspired by the now-decommissioned dilution refrigeration tanks for Badger and Sunshine—two of Yale’s earliest quantum computers. Badger holds the honor of running the world’s first demonstration of two-qubit algorithms with a superconducting quantum processor in 2009. Meanwhile, Sunshine held the honor of laying in parts on the floor of the office that I used during my artist residency when I first arrived at YQI. (For more information on Yale’s history of quantum hardware, see the exhibition description “The Quantum Revolution: Handcrafted in New Haven.”) It was important to me that our forest of light be formed from the accumulation of identical, modular objects—each beacon the same and interchangeable.

Yale’s decommissioned “Badger” quantum computer (hanging, left) as compared to a beacon prototype (standing, right).

Taking rough measurements of Sunshine’s thermal casing at the Yale Quantum Institute.

Similarly, I was attached to the idea that each beacon be wireless—both as an aesthetic choice, as well as for the concern of visitors who would be walking in the dark around these beacons. (Visitors shouldn’t be given the opportunity to trip over cables, of course.)

Alpay Kasal and his team at Bignoodle prototyped and constructed the beacons, each containing 75 individually addressable LEDs, an ultrasonic proximity sensor, a wifi-enable microcontroller, and a battery pack. Upon activation, each beacon connects to our wifi network to both report the status of its proximity sensor and to receive color commands. This is orchestrated by our custom controller software running from a conductor laptop, featuring Yue Wu’s open-source “Fusion Blossom” quantum error correction routines.


None of this work would be possible without the students, faculty, and staff of the Yale Quantum Institute, who patiently indulged my naive curiosity, graciously showed me around their labs, snuck me into dining halls, signed copies of their books, and came to hear me give talks about whatever it is that I do as a supposed graphic designer or XR expert. In particular, I owe a debt of gratitude to Florian Carle, who somehow never lost patience with me despite often having every reason to do so.

Florian returning a collection of beacons from the Green to YQI for storage. Until next time.