Research at GTQI - Quantum Information Processing

Microfabricated ion traps

A major challenge for the future is to increase the number of trapped ions that can interact to perform quantum processing from the present values, near 10 ions, to hundreds of ions in 2D arrays.

There is an aggressive program to design, fabricate, and test reliable, scalable chip-based traps at GTRI. Traps are designed at GTRI using advanced electromagnetic modeling techniques applicable to a wide range of trap architectures of interest to the trapped ion research community, and they are fabricated using scalable silicon VLSI technology based at the Georgia Tech Microelectronics Research Center (MiRC). Processes are now in place to fabricate advanced trap features, including multi-level electrode addressing using vias. Soon GTRI will have the capability to produce a trap with integrated mirrors for high efficiency light collection and optical access slots for vertical laser access through the trap. Ion trapping and testing labs at GTRI are used to characterize the trap performance and insure reliability as well as rapid feedback to the design and fabrication functions. Packaging processes for the traps are available for a variety of ultra-high vacuum (UHV) setups.

Dick Slusher, GTRI, MiRC

Photonic coupling

Techniques and protocols for coupling ion qubits to optical and microwave photons will be developed and implemented. These couplings provide natural primitives for quantum communication and the transfer of quantum information and entangled states within a quantum processor. Both free space and cavity based coupling schemes will be explored. Ions in cavity resonators may also be of interest as nonlinear beam splitters for enhanced resolution quantum imaging devices.

Michael Chapman, Alex Kuzmich, Brian Kennedy, Dick Slusher, and Li You

Neutral atom and molecule systems

Neutral atom systems will continue to be developed using ultra-cold atoms. Although the current state-of-the art in neutral atom systems lags behind the ion based systems, there are advantages to scaling to large numbers of qubits in the atom systems because of the flexibility of various trapping techniques and the absence of coulomb interactions between the trapped particles. It is anticipated that the extensive technology developed for creating and studying neutral quantum degenerate gases will be applied to quantum information processing.

Trapped dipolar molecules is another interesting direction since the trap density can be very high and the qubits, based on rotational states of dipolar molecules, can be tuned in and out of resonance with microwave fields with control voltages beneath the trapping regions. This qubit implementation has the enormous advantage that it would not require laser control of the qubit states.

Ken Brown, Michael Chapman, Brian Kennedy, Alex Kuzmich, Chandra Raman, Dick Slusher, and Li You

Algorithms, architectures and logic gates

New quantum algorithms are still emerging from the exploration of quantum information; a new one was discovered as recently as January 2007. The Institute plans to continue searching for new algorithms and studying applications for those already discovered.

Implementing these algorithms in a physical quantum computer is a very challenging task. Errors in the physical qubit gates are presently several orders of magnitude higher than those that are expected to result in fault tolerant quantum computing. There remains much work to be done in the area of quantum error correction in order to understand the optimum error correcting processes.

The architecture of the quantum computation is also a field that is just beginning to evolve. How can we optimize concurrency, number of physical qubits, quantum gate function, communication between qubits, quantum memory, classical programming and depth of computation (time interval for completing a computation)? This space of variables for quantum computation is just beginning to be explored.

Jean Bellissard