Nanoscale Mirrored Cavities Amplify, Connect Quantum Memories

Diamond photonic crystal cavities

Building quantum memories on a chip: Diamond photonic crystal cavities (ladder-like structures) are integrated on a silicon substrate. Green laser light (green arrow) excites electrons on impurity atoms trapped within the cavities, picking up information about their spin states, which can then be read out as red light (red arrow) emitted by photoluminescence from the cavity. The inset shows the nitrogen-vacancy (NV)-nanocavity system, where a nitrogen atom (N) is substituted into the diamond crystal lattice in place of a carbon atom (gray balls) adjacent to a vacancy (V). Layers of diamond and air keep light trapped within these cavities long enough to interact with the nitrogen atom's spin state and transfer that information via the emitted light. Photo credit: MIT

The idea of computing systems based on controlling atomic spins just got a boost from new research performed at the Massachusetts Institute of Technology (MIT) and Brookhaven Lab’s Center for Functional Nanomaterials (CFN). By constructing tiny "mirrors" to trap light around impurity atoms in diamond crystals, the team dramatically increased the efficiency with which photons transmit information about those atoms' electronic spin states, which can be used to store quantum information. Such spin-photon interfaces are thought to be essential for connecting distant quantum memories, which could open the door to quantum computers and long-distance cryptographic systems. 

Crucially, the team demonstrated a spin-coherence time (how long the memory encoded in the electron spin state lasts) of more than 200 microseconds—a long time in the context of the rate at which computational operations take place. A long coherence time is essential for quantum computing systems and long-range cryptographic networks.

"Our research demonstrates a technique to extend the storage time of quantum memories in solids that are efficiently coupled to photons, which is essential to scaling up such quantum memories for functional quantum computing systems and networks," said MIT's Dirk Englund, who led the research. Scientists at the CFN helped to fabricate and characterize the materials.

To learn more about this advance that could lead to quantum computing and the secure transfer of information over long-distance fiber optic networks visit: www.bnl.gov/newsroom/news.php?a=11695

2015-5591  |  INT/EXT  |  Newsroom