Center for Theoretical Physics' team evaluates principles of quantum gravity with wormhole connection

A team of scientists from the Center for Theoretical Physics is spearheading efforts to evaluate the principles of quantum gravity using a quantum processor.

In a newly published article in the journal Nature, a team of scientists from the Massachusetts Institute of Technology (MIT), Caltech, Harvard University and other institutions has demonstrated encouraging outcomes for the advancement of quantum computing. 

The scientists, in a groundbreaking achievement, have been able to transmit quantum information across a quantum system, akin to traversing a wormhole in interstellar space.

This recently conducted experiment did not involve any distortion of physical space and time, as portrayed in science fiction literature, but its results indicated that qubits were able to move from one system of entangled particles to another, simulating the concept of gravity. 

The Sycamore quantum processor device, developed by Google, was used to carry out the experiment, which has paved the way for more investigations using quantum computers to explore string theory and gravitational physics.

Daniel Harlow, a researcher at the MIT Laboratory for Nuclear Science (LNS), shared the interworks of the quantum system. Harlow works with David Kolchemeyer, one of the lead authors of the study.

"Simulating strongly interacting quantum systems, such as those that arise in quantum gravity, is one of the most exciting applications of quantum computers," Harlow said. "This is a promising initial step."

The team of physicists, including Kolchmeyer and Alexander Zlokapa from MIT's Center for Theoretical Physics (CTP) and LNS, have published in a recent Nature journal. 

They have presented the findings of their study on a duo of quantum systems that exhibit similar behavior to a traversable wormhole. Typically, a wormhole is a link between two far-off regions of spacetime, which, in the classical general theory of relativity, doesn't allow anything to travel through it. 

In 2019, however, Harvard University's Daniel Jafferis and his colleagues theorized that a wormhole could be traversable if entangled black holes created it. 

During his Ph.D studies, Kolchmeyer, who works with CTP and LNS researchers Harlow and assistant professor Netta Engelhardt, was advised by Jafferis, leading him to uncover new areas to study.

"These physicists discovered a quantum mechanism to make a wormhole traversable by introducing a direct interaction between the distant spacetime regions, using a simple quantum dynamical system of fermions," Kolchmeyer said. 

The latest research paper's primary authors are Jafferis and Caltech professor Maria Spiropulu. 

Leading the study were authors Kolchmeyer and Zlokapa, along with Joseph Lykken from Fermilab Quantum Institute and Theoretical Physics Department, and Hartmut Neven from Google Quantum AI. 

Other contributors to the paper are Samantha Davis and Nikolai Lauk from Caltech and the Alliance for Quantum Technologies (AQT). 

Kolchmeyer noted that their work has revealed wormhole teleportation.

"In our work we also used these entangled quantum systems to produce this kind of ‘wormhole teleportation’ using quantum computing and were able to confirm the results with classical computers," Kolchmeyer said. 

For this experiment, scientists used the Sycamore 53-qubit quantum processor to teleport a quantum state from one quantum system to another, effectively transmitting a signal "through the wormhole." 

To accomplish this, the research team needed to identify entangled quantum systems that displayed the characteristics predicted by quantum gravity, while remaining small enough to run on contemporary quantum computers.

The individual who started this research as an undergraduate in Spiropulu's lab is currently a second-year graduate student in physics at MIT.

"A central challenge for this work was to find a simple enough many-body quantum system that preserves gravitational properties," Zlokapa said. 

The research team utilized machine-learning approaches to accomplish this feat. They took complex quantum systems with a high-degree of interaction and gradually reduced their connectivity. This learning process resulted in several examples of systems that exhibited behavior consistent with quantum gravity, with each example requiring only approximately 10 qubits - an ideal size for the Sycamore processor. 

Team members then measured the amount of quantum information that flowed from one quantum system to another, based on the type of shockwave applied, whether positive or negative.