By Anne Broadbent, IQC Postdoctoral Fellow
When Christopher Columbus set out to discover a route to the orient, he conjectured that by sailing due West, he would find a more efficient route to the much-coveted treasures of the East. Conventional wisdom cautioned that, in the process, he would fall off the edge of the Earth.
Quantum information scientists are sailing in uncharted waters. How do we know we are going in the right direction? Akin to using a sextant to shoot the sun, we have developed a toolbox to help us evaluate progress and adjust our course when required.
This week, a group of scientists from around the world met for the 2012 “Quantum Characterization, Verification and Validation Workshop” in Bethesda, Maryland. Typical questions being discussed and debated were: “How do we know if we correctly built a quantum device?”, “Can we establish standard benchmarks for quantum technologies?” and “Could a small quantum device be used to verify a larger one?”
Breakthroughs occasionally require bold actions that defy conventional thinking. In the case of quantum characterization, verification and validation, this involves questioning some of the established techniques — such as the ubiquitous yet ill-motivated use of a technique called “maximum likelihood estimation.” The consensus at this workshop is that our common goal should be to somehow master a quantum system’s entropy (a technical term referring to uncertainty), thereby enabling smooth sailing towards our final destination of full-scale quantum computers.
En route toward the elusive quantum computers, however, we will unavoidably reach the point where computational intractability limits our ability to make predictions on quantum experiments (indeed, there is strong evidence that this day is fast approaching). One of the themes in this workshop is how techniques from complexity and cryptography can help circumvent these limitations.
Given the attendees’ varied backgrounds, conflict is unavoidable and even desirable. One memorable debate on verifying quantum devices in the presence of systematic errors ended in an exclamation from one experimentalist that “Numbers are only correct in theory!” A welcome addition to the workshop is the online collaborative site — a feature that has allowed participants to focus on key questions ahead of time, as some discussions were launched a week before the workshop.
Christopher Columbus did not, of course, fall off the edge of the Earth, but instead discovered a wonderful New World. This week’s workshop has aided our navigation toward the new quantum world.