Quantum Lunch Series Event – Speaker Lex Kemper

Talk Title: Many-Body Thermodynamics on Quantum Computers via Partition Function Zeros

Speaker:  Dr. Lex Kemper is an Associate Professor in the Department of Physics at NC State.

Abstract:  Interacting quantum systems illustrate complex phenomena including phase transitions to novel ordered phases. The universal nature of critical phenomena reduces their description to determining only the transition temperature and the critical exponents. However, numerically calculating these for systems in new universality classes is complicated due to critical slowing down, requiring increasing resources near the critical point. An alternative approach is to calculate the partition function.

The partition function is a fundamental object in statistical physics.  Simply put, it is the count of the number of states at a particular set of thermodynamic state variables (e.g. temperature, number of particles, and volume). Beyond that, its derivatives reveal measurable thermodynamic quantities: free energies, heat capacities, etc.  Calculating the partition function is thus a path towards studying the thermodynamics of interacting quantum systems and their phase transitions.

One way to obtain the partition function is to analytically continue the calculation onto the complex plane and determines the partition function via its zeros. We show how to robustly perform this analysis on noisy intermediate scale trapped ion quantum computers in a scalable manner, using the XXZ model as a prototype.  We illustrate the transition from XY-like behavior to Ising-like behavior as a function of the anisotropy. While quantum computers cannot yet scale to the thermodynamic limit, our work provides a pathway to do so as hardware improves, allowing the determination of critical phenomena for systems that cannot be solved otherwise.

This is a Virtual Event.

For more information email:

quantumcomputing@ncsu.edu