Technology that encodes information in photons (particles of light) could lead to vastly increased speeds of telecommunications and computing and significantly enhanced levels of cybersecurity – and a quantum computing revolution.
However, to date, quantum information processing has only been shown in some materials, many of which would be impractical to manufacture because of limitations of size, or the need to keep them at ultra-low (cryogenic) temperatures.
Now, for the first time, researchers from the University of Technology Sydney (UTS) have developed a room temperature, thin material that emits single photons. The results were announced in a letter published in Nature Nanotechnology on 26 Oct 2015.
Quantum information processing
Quantum information processing seeks to use photons to encode information to create a quantum ‘bit’ of information, or qubit. Qubits are to quantum computers what bytes are for computers today – a vital ‘unit’ of information. But qubits can operate much faster than the bytes we use in computing today, and because of their nature could revolutionise not only computing speeds but also cybersecurity, as they can encrypt information in a near flawless system.
Previously, single-photon-emitting devices have been created in semiconductors such as diamond and silicon carbide, or exotic materials such as nanocrystal quantum dots or carbon nanotubes, the researchers say. But ideally, a quantum computing chip would need to be created from a product that is easily manufactured.
“We found the first 2D, single photon emitter that works at room temperature,” said Professor Mike Ford, Associate Dean (Research and Development), Faculty of Science at UTS and co-author of the new study.
“There are other 2D materials that emit single photons but you have to freeze them down to liquid nitrogen or liquid helium temperatures [-200°C to -269°C],” he said.
Two-dimensional materials are crystalline structures consisting of a single layer of atoms. A well-known 2D material is graphene – a hexagonal lattice of carbon atoms. Researchers at UTS used defects in single layers of hexagonal boron nitride to explore the materials’ quantum emitting properties and found that it was able to emit a single photon in one unimaginably tiny pulse of light.
“That’s important because one of the big goals is to make optical computer chips that can operate based on light rather than electrons, therefore operating much faster with less heat generation,” said Ford.
“Traditional LEDs [Light Emitting Diodes] emit a stream of photons. But by making light sources that emit one photon at a time, you can control the emission of individual photons,” he said.
This is critical to the development of quantum communication technologies because single photons are needed in order to tap into the quantum effects of particles.
“The emission of individual photons is important for quantum communications because it means that encryption techniques can be put in place to make systems more secure,” said Ford.
“You can create very secure communication systems using single photons,” explained Associate Professor Igor Aharonovich. “Each photon can be employed as a qubit (quantum bit, similarly to standard electronic bits), but because one cannot eavesdrop on single photons, the information is secure.”
Quantum computing revolution
This breakthrough could open new opportunities in quantum optics, a field of quantum physics dealing specifically with the interaction of photons with matter, and could herald the beginning of a transition to technologies and devices using photons, rather than electrons, to carry information.
Because hexagonal boron nitride emits quantum photons at room temperature, it can be placed into very small devices, like nanophotonic circuits.
“This material is very easy to fabricate,” said PhD student Trong Toan Tran. “It’s a much more viable option because it can be used at room temperature; it’s cheap, sustainable and is available in large quantities.”
“Ultimately we want to build a ‘plug and play’ device that can generate single photons on demand, which will be used as a first prototype source for scalable quantum technologies that will pave the way to quantum computing with hexagonal boron nitride,” he said.
– Carl Williams