The Incremental Quest for Quantum Computing

Researchers are on the threshold of building feasible quantum computers, with a few architectures inching ahead. Will we soon see a quantum leap in their progress?

For more than two decades, one of the holy grails of physics has been to build a quantum computer that can process certain types of large-scale, very difficult problems exponentially faster than classical computers. Physicists are making progress toward this goal every day, but nearly every part of a quantum computer still needs re-engineering or redesign to make it all work. Current research is focusing on every angle of the quantum computer problem, including: new types of sources and ways to generate entangled photon pairs, new types of gates and their fabrication on chips, refined ways to create and control qubits, new designs for storage/memory buffers, “nondemolition” detectors, and ways to optimize them in various combinations. In spite of the difficulty with pulling all these pieces into one cohesive “winning” platform, researchers in the field agree it’s a matter of when – not if – quantum computing systems will be practical. Many predict 10 to 15 years.

The creation and control of a single qubit is inherently difficult, but controlling many of them simultaneously is even harder. Quantum states are fundamentally limited for the same reasons that the number of transistors on a semiconductor board is limited, according to Christopher Monroe, professor of physics at the University of Maryland’s Joint Quantum Institute in College Park. The more of them you have, the more difficult it is to connect them and the noisier the system.