Georgia Tech Research Institute (GTRI) scientists work in an optical lab developing improved ion traps that could be used in quantum computing. Shown are (l-r) research scientists Jason Amini and Nicholas Guise. Photo: Rob Felt.
Increasing the number of connections on the edges of chips could move us closer to a quantum computer system
Quantum computers are in theory capable of simulating the interactions of molecules at a level of detail far beyond the capabilities of even the largest supercomputers today. Such simulations could revolutionize chemistry, biology, and materials science, but the development of quantum computers has been limited by the inability to increase the number of quantum bits, or qubits, that encode, store, and access large amounts of data.
In a paper published in the Journal of Applied Physics, a team of researchers at the Georgia Tech Research Institute (GTRI) and Honeywell International have described a new device that allows more electrodes to be placed on a chip.
“To write down the quantum state of a system of just 300 qubits, you would need 2300 numbers, roughly the number of protons in the known universe, so no amount of Moore’s Law scaling will ever make it possible for a classical computer to process that many numbers,” said Nicholas Guise, the GTRI research scientist who led the research. “This is why it’s impossible to fully simulate even a modest-sized quantum system, let alone something like chemistry of complex molecules, unless we can build a quantum computer to do it.”
While existing computers use classical bits of information, quantum computers use “quantum bits” or qubits to store information. Classical bits use either a 0 or 1, but a qubit, exploiting a weird quantum property called superposition, can actually be in both 0 and 1 simultaneously, allowing much more information to be encoded. Since qubits can be correlated with each other in a way that classical bits cannot, they allow a new sort of massively parallel computation, but only if many qubits at a time can be produced and controlled. The challenge the field has faced is scaling this technology up, much like moving from the first transistors to the first computers.
One leading qubit candidate is individual ions trapped inside a vacuum chamber and manipulated with lasers. The scalability of current trap architectures is limited because the connections for the electrodes needed to generate the trapping fields come at the edge of the chip, and their numbers are therefore limited by the chip perimeter.
The GTRI/Honeywell approach uses new microfabrication techniques that allow more electrodes to fit onto the chip while preserving the laser access needed. This work was funded by the Intelligence Advanced Research Projects Activity (IARPA). — AMERICAN INSTITUTE OF PHYSICS