Optical quantum computing: science-fiction, horror-story or news?
Alexei Gilchrist, NK Langford, Jeremy L. O’Brien, GJ Pryde, Timothy C. Ralph, TJ Weinhold, AG White · Bristol Research (University of Bristol) · 2005
Quantum computing is the lovechild of quantum physics and computer science. In this talk we look at what quantum computation is, why physicists, chemists and computer scientists might want to do it, and where we are today. There are many possible physical architectures for realising a quantum computer, we will focus on optical quantum computing, where the information is encoded and manipulated using single photons. Formany years this was thought to be science-fiction, but with the discovery of measurement-induced nonlinearity there has been an explosion of interest world-wide, and a slew of ”firsts” in demonstration systems. Scaling up from these small systems to a large error-free computer is possible in principle: at first it was thought it would take horrific numbers of ”physical” gates per ”logical” gate. Recently proposed schemes reduce these overhead requirements from the order of 10,000 to 50, and possibly even 1 - great news if you’re an experimentalist! Finally, we will look briefly at some of the scientific and technological challenges ahead, and present our latest experimental results where we build a small optical quantum system for quantum chemistry, calculating the properties of molecular hydrogen to an accuracy of 20 bits.