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Carmen Jeannette Stepek

Carmen Jeannette Stepek


California State University, Channel Islands



Site Abroad: 

Trinity College Dublin, Ireland


Steve Campbell

Faculty Sponsor(s): 

John Goold

Faculty Sponsor's Department: 


Project Title: 

Quantum Thermodynamics of a Qubit

Project Description: 

The work of Thermodynamics and energetics of quantum systems group, also known as QuSys, unifies a variety of topics in physics; from thermodynamics and quantum information theory to condensed matter theory and non-statistical mechanics. During my internship with QuSys, I observed the dynamic methods of Dr. John Goold’s theoretical research lab and eventually established an individual investigation of physics at the quantum level. As I learned foundational theories, I was gradually introduced to concepts specific to quantum computation. To better grasp the counter intuitive concepts I was studying, it was essential that I uncoupled my understanding of mechanics and energetics from classical laws of physics. Once I had sufficient knowledge of operators, quantum bits (“qubits”) and the Bloch sphere, I wrote a Matlab program to evaluate the maximum work extractable (“ergotropy”) and the von Neumann entropy using the Hamiltonian and an arbitrary density matrix of a qubit, a two-state system. Pure state evolutions along the surface of the Bloch sphere did not yield any von Neumann entropy. Entropy peaked when the system was defined by a maximally mixed state, near the center of the Bloch sphere, but ergotropy deteriorated. When I prepared the system in a gibbsian state, no work could be extracted due to a net-zero energy change. The von Neumann entropy of the system and ergotropy generated were incongruous. I will continue to strengthen my critical thinking and computational skills to better follow quantum problems in prospective research as QuSys leads some of the most influential investigations of quantum thermodynamics.