IQC Researchers Tune Photons to Interact with Caesium Atoms

Researchers at the Institute for Quantum Computing at the University of Waterloo have demonstrated a technique to facilitate long-distance quantum communication by utilising the frequency of photons to interact with atoms, serving as potential quantum memory nodes. The team employed a nanowire quantum dot photon source, fine-tuning its frequency via a frozen nitrogen layer to achieve resonance with caesium atoms. This precise spectral tuning, conducted at temperatures approaching absolute zero within a cryostat, enabled improved quantum information sharing and represents a previously unachieved demonstration, according to lead author Dr Rubayet Al Maruf. The approach aims to establish stable quantum memory for photons, enhancing the fidelity and longevity of quantum information transfer.

Researchers at the Institute for Quantum Computing (IQC) at the University of Waterloo have demonstrated a technique to connect quantum devices over long distances, representing a crucial step towards realising a functional quantum internet. A primary limitation in quantum communication is the restricted range over which quantum information can be transmitted, as essential properties like entanglement cannot be amplified in the same way as classical signals without disrupting the information. This research focuses on utilising the frequency of photons to interact with atoms, which can then function as memory nodes to distribute entanglement between distant locations.

The team employed a nanowire quantum dot as a photon source and successfully fine-tuned its frequency to improve quantum information sharing. This tuning was achieved by freezing a thin layer of nitrogen gas onto the nanowire’s surface, enabling the emission of photons at a frequency resonant with caesium atoms. Dr Rubayet Al Maruf, research associate at IQC and lead author of the paper, explained that this technique allows for precise tuning of photons from the quantum dot to match specific spectral features of atoms, akin to accurately tuning a guitar string.

Sreesh Venuturumilli, a PhD student at IQC, added that the tuning process is critical for establishing the necessary interaction between photons and atoms, paving the way for more efficient and reliable quantum communication networks. The use of cold atoms within the system is intended to provide a stable quantum memory for the photons, enhancing the longevity and fidelity of quantum information transfer, and facilitating quantum entanglement distribution. This demonstration was conducted within a cryostat at temperatures approaching absolute zero, representing a previously unachieved result.