Probe light signal breakthrough in quantum computing

When HP Labs’ Quantum Information Processing Group started researching the possibility of using photons (light particles) for information processing, they found out that the best feature of photons also happen to be their biggest flaw. Sending light over long distances for communication – with optic fibers, for example – doesn’t do damage to its condition. This is because in the process of transfer bits of light don’t talk to other bits of light, or with anything else. With the use of photons, one can engage in a number of conversations simultaneaously in the same telephone cable and they won’t interfere with each other. Here lies the problem as well. According to HP Distinguished Scientist Tim Spiller, who is also research leader for optical quantum computing, “To do any kind of data processing, the bits of data need to be able to interact. So on the face of it, light isn’t good for information processing because the bits of light don’t talk to each other. We need a process to get pieces of light at the quantum level to talk to each other.” And this was the process his team – together with Principal Research Scientist Bill Munro, other HP Labs researchers, and Tokyo-based National Institute of Informatics associate professor of quantum information sciences Kae Nemoto -has tried to develop for the past two years.

When HP Labs’ Quantum Information Processing Group started researching the possibility of using photons (light particles) for information processing, they found out that the best feature of photons also happen to be their biggest flaw. Sending light over long distances for communication – with optic fibers, for example – doesn’t do damage to its condition. This is because in the process of transfer bits of light don’t talk to other bits of light, or with anything else. With the use of photons, one can engage in a number of conversations simultaneaously in the same telephone cable and they won’t interfere with each other. Here lies the problem as well. According to HP Distinguished Scientist Tim Spiller, who is also research leader for optical quantum computing, “To do any kind of data processing, the bits of data need to be able to interact. So on the face of it, light isn’t good for information processing because the bits of light don’t talk to each other. We need a process to get pieces of light at the quantum level to talk to each other.” And this was the process his team – together with Principal Research Scientist Bill Munro, other HP Labs researchers, and Tokyo-based National Institute of Informatics associate professor of quantum information sciences Kae Nemoto -has tried to develop for the past two years.

Before the process can be fully started they needed to overcome one big hurdle: detecting individual chunks of light without absorbing or damaging them. In a normal process, a single photon is detected by letting it hit something (a piece of semiconductor material, perhaps). As Spiller explained, “That creates a lot of electrons and holes, and the piece of light is lost. So you can detect it, but in the process of doing so, it’s destroyed.” With the use of a probe light signal it seems like the team has finally made an important breakthrough. The team has hit two birds with one stone: they can now make photons communicate with each other via a probe light signal; this leaves an imprint, which makes detection of photons possible without damaging them. And although the communication happens in an indirect manner, it is good enough. “If you do a certain type of measurement on the probe after it’s talked to two photons, you’ll find that although they don’t talk directly to each other, the photons have interacted because they both talk to the probe,” Spiller explains.

Why the interest in quantum computing and the use of light for coomunication, you say. This innovation has the potential to revolutionize information technology. It can lead to the development of faster, more powerful, and more secure computer networks in the future. Processors which will utilize quantum computing can do tasks that today’s most powerful supercomputers cannot perform. And as Munro pointed out, who knows where else this development can lead. Comparing their discovery to the initial use of transistors only in hearing aids, he mentions that other applications are sure to come up for their discovery as well. Spiller however reiterates that quantum computing will enhance, rather than replace, conventional computing. He says, “We believe quantum computing will grow alongside conventional computing. You might have a quantum processor sitting next to your conventional machine. It’s not that quantum technology will sweep everything else away. Instead, it will enable new things.”

The technology is still far from being a full-blown thing. The current discovery with photons is but a small step. Spiller is positive though, “We hope to have some experimental results in the next couple of years. Once we’ve got that started — once we know for sure how one photon can talk to one beam — we can go forward to build quantum processors.”