Quantum Computing with Neutral Atoms: Quantum Gates and Maxwell’s Demons

I will describe our plans for building a quantum computer based on cesium atoms trapped in a 3D optical lattice. I will detail how, using targeted phase shifts, we implement high fidelity (0.996) and low crosstalk (0.0021) site-selective single qubit gates on any site in a 5x5x5 lattice. We initially load half the lattice sites with a single atom, and after projection sideband cooling 85% of the atoms are in their vibrational ground states. With atoms this cold, most of the system entropy is associated with this random half filling of the lattice. Using site-selective state flips and state-dependent lattice translations, we have prepared nearly perfectly filled sub-lattices. The sorting process can be viewed as an implementation of Maxwell's demon on these ~60 particles. Generation of the initial site-occupancy map lowers the entropy of the system, and the sorting process uses that information to reversibly make a state of manifestly low entropy. Our Maxwell demon increases the phase space density of the system enough so that were the lattice to be adiabatically shut off, the atoms would have crossed the quantum degeneracy threshold. I will also briefly touch upon our plan to implement Rydberg gates in this system to generate entanglement.