Researchers from CRANN and the School of Physics at Trinity have created a new device that can emit photons from quantum dots. This innovative device could be a key step in the development of quantum computing, quantum communications and other quantum devices.
The team has improved on previous designs of photonic systems. The new device allows for controllable, directional emission of single photons and produces entangled states of pairs of quantum dots. Quantum dots are essentially nanoscale materials, often man-made crystals, that can emit quantum particles such as electrons and photons.
Professor John Donegan of CRANN and Trinity’s School of Physics explained: “The device works by placing a metal tip within a few nanometers of a surface containing the quantum dots.”
“The tip is excited by light and produces an electric field of such enormous intensity that it can greatly increase the number of single photons emitted by the dots,” Donegan continued. “This strong field can also couple emission from pairs of quantum dots, entangling their states in a way that is unique to quantum emitters of light.”
For applications such as quantum computing, the emitted particles must be entangled. Quantum entanglement is a fundamental property of quantum mechanics and occurs when two or more particles are “linked” through their states. Quantum states could be the spin or momentum of a particle. The quantum state of each particle is dependent on the state of the other linked particle. Any action performed on one of the entangled particles will affect the other particle, even when the entangled particles are separated by large distances. This phenomenon is essential in the development of quantum computing.
Quantum computers utilise the properties of quantum bits, known as “qubits”. These qubits are the quantum analog of classical computer’s binary bits. Current computers store information in bits of either 0s or 1s. Qubits can be 0 and 1 simultaneously. This means that quantum computers could execute computations much faster than current computers, and will overall have much greater computational power over current computers. In this device, the quantum properties of light at a nanoscale can be used as qubits.
Professor Ortwin Hess, Professor of Quantum Nanophotonics in Trinity’s School of Physics and CRANN, outlined: “By scanning the metal tip over the surface containing the quantum dots, we can generate the single photon emission as required.”
“Such a device is much simpler than current systems that attempt to fix a metal tip, or a cavity, in close proximity to a quantum dot. We now expect that this device and its operation will have a striking effect on research in quantum emitters for quantum technologies,” Hess said.
The team plans to fabricate more devices that can demonstrate controlled emission of photons in an effort to contribute to the growing field of quantum technology here in Ireland.