Research
Quantum Gravity, Quantum Computation, and the Nature of Reality
Overview
My primary research interest lies in the field broadly referred to as quantum gravity. I did my graduate training at Pennsylvania State University, under Prof. Stephon Alexander and Prof. Martin Bojowald. My graduate work involved applying ideas from many-body phenomena to cosmology.
In particular we explored whether a four-fermion attraction between fermions mediated by the gravitational connection could lead to the formation of a cosmological fermionic condensate. This work further led us to propose a possible resolution to the cosmological constant problem.
With my advisor and co-workers I also explored the possibility that the acceleration of the universe as induced from measuring supernovae redshifts and fitting with CMB data from the WMAP satellite could in fact be attributed to the possibility that our solar system is located in the interior of a cosmological void spanning ~100–150 mega parsecs.
While at Penn State I was also able to learn about Loop Quantum Gravity, which is considered the main competitor to String Theory as a candidate theory of quantum gravity. With my collaborator Sundance Bilson-Thompson, I have written an introductory text on LQG, titled LQG for the Bewildered, published in 2017 by Springer Nature.
There is a common thread which runs through all my work — the desire to understand how best to formulate a complete, consistent theory of quantum gravity. For this purpose I have employed various tools from quantum information, many body physics and canonical quantum gravity.
Research Areas
Loop Quantum Gravity
Canonical quantization of general relativity, spin networks, and the discreteness of spacetime geometry.
Quantum Computation
Quantum algorithms, error correction, and the relationship between quantum gravity and quantum information.
Many-Body Physics
Tensor networks, quantum phase transitions, and their applications to quantum gravity.
Elementary Particles
Embedding particles in LQG, braiding models, and scattering in semiclassical states.
Recent Work
Arrow of Time from Symmetry Breaking
In ProgressUsing tensor network techniques to make time-reversal symmetry into a local gauge symmetry in spin-networks, exploring whether symmetry breaking can give rise to a macroscopic cosmological arrow of time.
Coherent States & Particle Scattering
PublishedWith Devadharsini Suresh, showed that degrees of freedom on spin network edges can be interpreted as particles with definite momenta using coherent intertwiners representing classical geometry.
Quantum Error Correction in LQG
PublishedRecognized the relationship between Bilson-Thompson's topological particle model and a three-qubit quantum error correcting code, with natural embedding in spin networks.
LQG ↔ String Theory Connection
PublishedExplored connections between String Theory and LQG via quantum geometry, examining how discrete LQG structure affects stringy models.
Future Directions
LQG and String Theory
Concretely establish the relationship between these two fields. In a discrete background, conformal symmetry of the string worldsheet will be broken — potentially providing loop-string solutions in 4D without compactifications or supersymmetry.
Experimental Signatures
The upgraded LHC presents opportunities for searching quantum gravity signatures. At the Planck scale, local symmetry may become SL(2,Z), manifesting as gaps or steps in particle spectra from hadron collisions.
LQG, Holography & Quantum Computation
Continue work on the correspondence between standard model particles and unitary gates for universal quantum computation, providing concrete mathematical foundations.
Tensor Category Theory
Tensor category theory provides the appropriate tools to pose the problem and write down a candidate system of equations for quantum gravity.
History & Motivation
The problem of quantum gravity is the outstanding problem of our generation. Since as long as I can remember I have wanted to work on this grand project of unification of all forces and interactions.
When I applied to graduate schools at the end of my BSc in 2003 it would have been natural to choose String Theory. I was unaware of the controversies regarding the subject, and works by authors such as Peter Woit and Lee Smolin critical of the stringy paradigm had yet to be written.
I happened to chance upon an alternative: Loop Quantum Gravity. What captured my attention was the fact that LQG claimed to have understood how to quantize geometry itself. The idea that spacetime itself should be a quantum mechanical construct held deep intuitive meaning for me.
I felt motivated strongly enough to drive some eight hundred miles from Rolla, Missouri to Penn State in my 1992 Toyota Camry to meet one of the leading lights of the field — Prof. Abhay Ashtekar.
I ended up applying to four places: Harvard, Washington University, UT Austin and Penn State. I was accepted at all of them except Harvard. Ultimately I went with my gut feeling and chose Penn State.
Now some twenty years and many rejected papers later one might think that I regret my choice of LQG over String Theory. I do not. This has led me to study the AdS/CFT correspondence, quantum computation, tensor networks and many body physics.
Publications
A complete list of publications is available on INSPIRE-HEP, the canonical database for high-energy physics literature.
View on INSPIRE-HEP