Quantum computers are hailed as revolutionary instruments, easily more powerful than the most powerful supercomputer we can build. But there are many hurdles to cross before we get there. Researchers have reported how they just jumped over one of them.
Quantum computers employ the laws of quantum mechanics to go beyond classical capabilities. The crucial aspect is to create stable quantum architectures. Easier said than done. The new work published in Physical Reviews Letter showed an incredible 100-fold increase in efficiency in creating pairs of entangled photons, something never achieved before.
Entanglement is a fascinating and puzzling concept, at least from our point of view. When two particles are entangled, manipulating one will result in changes in the other instantaneously, no matter how far apart they are. This is because they are not exactly two particles in the classical sense; they are a single quantum system.
Entanglement is a key component of quantum communication. These entangled photons allow the transfer of information between two nodes, and due to its nature, this type of communication is unhackable.
The new method has photons trapped in a nanocavity, where they can resonate and split into entangled pairs. The traditional method is not really efficient. It requires hundreds of millions of photons being shot via laser into the cavity to form a single entangled pair.
This new improvement is exciting as it required one-hundredth of that amount of light. Using their newly developed chip, researchers can now produce tens of millions of entangled photon pairs per second using a single (and simple) microwatt-powered laser beam.
“It’s long been suspected that this was possible in theory, but we’re the first to show it in practice,” senior author Professor Yuping Huang, from Stevens Institute of Technology, said in a statement. “This is a huge milestone for quantum communications.”
The breakthrough is due to several factors. The team uses high-quality and very reflective cavities carved into lithium niobate crystals. Photons bounce around in them with very little energy loss. The team also fine-tuned environmental properties, such as temperature.
The goal is to achieve one entangled pair per photon sent inside the cavity – a bold and difficult job. But the team is taking on the challenge. “It’s definitely achievable,” explained co-lead author Jiayang Chen. “At this point we just need incremental improvements.”
The success of quantum communication also relies on its ability to integrate with existing computers and infrastructure. The usage of optical chips that are efficient and cheap to operate will be key to their success.
