Quantum Computing with Synthetic Atomic Qubits

Trapped ions offer a premiere platform for testing and manipulating isolated quantum systems.  Atomic clocks, quantum sensors, and matter-wave interferometry all require exquisite isolation from the decohering effect of their environment.  It is by isolating these systems that we finally see nature as it behaves according to the rules of quantum mechanics.  It's not that quantum mechanics breaks down for the size and temperature scale of the "everyday world" we know, but rather that the effects of quantum interference become hidden in the noisy thermal average of the commony experienced universe at human scales.

A particularly vexing problem associated with trapped ion quantum systems (known as "qubits") is that the "easy to use" qubits aren't, well, easy to use.  The atomic structure that gives rise to the easiest high-quality qubit comes with the need for difficult laser technology in the ultraviolet.  However, this is only really true if we confine ourselves to the species that are found in natural abundance.  If we widen the scope to include human-produced isotopes, the 133Ba+ ion emerges as the atom that has it all -- an easy to use, robust qubit and optical transitions in the visible part of the spectrum.

In collaboration with Eric Hudson's group, we have developed methods to produce 133Ba+ in our trap and have performed preliminary spectroscopy of its internal structure.  The image here shows two 133Ba+ ions in the trap ("Dave" is the ion in the upper left, "Justin" is on the lower right), where by exchanging phonons of their collective modes of motion, the hyperfine qubits defined on each atom may be used to perform computations with quantum speed enhancements.