The Little Chip That Could
When it comes to quantum computing, less is sometimes more.
Take the new Hydra chip created under the DARPA Quantum Annealing Feasibility Study, directed by Daniel Lidar, USC Viterbi professor of electrical and computer engineering. This chip — which, like all chip generations in this project, is named after a constellation — has 25 qubits. Compared to the 5,000-plus qubits on the well-known D-Wave chip, that might not seem like much. Yet the team led by Lidar, which includes chip designers and fabrication experts from Northrop Grumman and MIT Lincoln Laboratory, has found a way to make the little Hydra chip, by some measures, 100 times more powerful for its size.
How? By improving the “quantumness” of the qubits on the chip. The power of quantum computing comes in part from a qubit’s ability to maintain its superposition — essentially existing in an on-and-off state at the same time. The longer a qubit can maintain that state, the more powerful its computing power. When not in superposition, a qubit is no less powerful than an old regular bit.
But the Hydra chip maintains its qubits in superposition much better than anything previously designed — 100 times longer than its D-Wave cousin. (Since 2011, the D-Wave chip has been at USC’s Information Sciences Institute, making USC Viterbi the first operational quantum computing center in academia.)
The Hydra is the latest in several generations of chips that the USC-led team has helped design. As part of a DARPA-funded program at USC called Reversible Quantum Machine Learning and Simulation (RQMLS), the goal is to use the 25-qubit chip to demonstrate rudimentary concepts in quantum machine learning and quantum simulation of exotic materials. In time, researchers plan to apply the techniques that give Hydra such staying power to larger chips. If scientists can one day combine Hydra’s ability to maintain superposition with D-Wave’s sheer number of qubits, we could enter a new phase of quantum computing.