Neutral atom quantum computing : Quantum gates and Maxwell's demon

Open Access
- Author:
- Kumar, Aishwarya
- Graduate Program:
- Physics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- January 25, 2019
- Committee Members:
- David Scott Weiss, Dissertation Advisor/Co-Advisor
David Scott Weiss, Committee Chair/Co-Chair
Nitin Samarth, Committee Member
Kenneth O'Hara, Committee Member
Benjamin James Lear, Outside Member - Keywords:
- Quantum Computation
Atomic Physics
optical lattice
neutral atoms
Cesium
rydberg
quantum gates
randomized benchmarking
laser
maxwell's demon
entropy - Abstract:
- Quantum computers might solve several problems thought to be intractable on classical computers. These include problems like the prime factorization of large numbers, searching over a solution space and simulations of complex quantum systems, out of which the latter is the most exciting for physicists. Over the past few years, the experimental technologies have matured enough that there has been a strong effort to build the first 50-100 qubit computers in several candidate systems, one of which is neutral atoms. Neutral atoms in light traps have been a leading technology for quantum simulations for many years, but when trapped in optical lattices, they are also promising qubit candidates for a scalable quantum computer. Over the past few years, exquisite control over positions and the internal states of individual atoms has been developed towards this goal. This thesis describes development of such control in our three dimensional array of Cesium atoms. We have developed an addressing scheme to target single atoms and execute high fidelity quantum gates without affecting the stored quantum information in neighboring atoms, a challenging feat in a 3D geometry. As we will see, atoms cannot be deterministically loaded in to these arrays, and typically only about half the sites have a single atom. Later in the thesis we use our single site control and combine it with state dependent lattices to move individual atoms and re-arrange them to yield fully-filled sub-lattices, creating nearly perfect registers of neutral atoms and initializing our quantum computer. We show that this atom "sorting" is an implementation of the famous "demon" thought experiment proposed by James Clerk Maxwell in 1872. Our experiment, like the demon, decreases the entropy of the system in the process of creating an ordered state from a random disordered one. Finally, we use our state dependent lattice to implement a loss-less state detection protocol with 20 times lower error than any other methods.