Title: New moves in spin choreography: quantum control of atomic qubits and qudits

Speaker: Poul Jessen, Center for Quantum Information and Control (CQuIC), College of Optical Sciences, University of Arizona.

Time and place: Thursday 31/10, 15:15, Phys. Aud.

Abstract:
The standard paradigm for Quantum Information Science involves a collection of qubits, whereas the physical systems considered as building blocks for a quantum processor or simulator often have more than two accessible levels. To take advantage of these higher-dimensional Hilbert spaces (qudits), it is necessary to develop a toolbox for quantum control similar to what already exists for qubits. Over the past several years we have used the 16-dimensional ground hyperfine manifold of individual Cs atoms as a testbed for such work. Driving the atoms with a combination of phase modulated rf and µw magnetic fields, we use numerical optimization techniques to design control waveforms (rf and µw phases as function of time) that accomplish a wide range of control tasks, from quantum state-to-state maps to full unitary transformations, with average fidelities that vary from >99% for the former to ~97% for the latter.  Restricting ourselves to qubits encoded in the ground manifold, the tools of inhomogeneous control can applied to the problem of resonance addressing and control of atoms in optical lattices, allowing us to target arbitrary single-qubit gates on desired sites or perform independent gates in parallel across adjacent sites.  Other applications of quantum control pursued by our group include an improved atom-light interface and spin squeezing, and an unconventional approach to quantum state and process tomography.

Coffee, tea and cake will be served at 15:05.

Annette Svendsen, Jacob Sherson and Aurelien Dantan