Experts agree that quantum information processing will usher in the next wave of computing and communication technologies for the 21st century. An essential component of these new technologies will be quantum memories, capable of precisely storing and releasing quantum information bits.
A quantum memory is much like a traditional computer memory that performs write, store, and read tasks, only it must be able to store complete quantum states not just ones and zeros. High-fidelity, efficiency, storage duration, and in particular, speed, are the key performance criteria by which quantum memory standards are measured. So far, quantum memories have operated with bandwidths that limit data rates to the MHz scale.
Dr. Benjamin Sussman, a researcher with NRC’s Steacie Institute for Molecular Sciences, was part of a two-year collaboration with Oxford to investigate the intersection of quantum control and quantum information. Leveraging the combined expertise from these two fields led to the breakthrough.
The quantum leap in speed is derived from their new technique’s ability use a high-speed laser control field to make atoms absorb light where they normally would not. This key modification has resulted in a massive improvement in storage and retreval speeds, with bandwidths exceeding 1 GHz! The Team’s article entitled, “Towards high-speed optical quantum memories,” illustrates that the memory bandwidth generated by the laser control fields allows for data transfer more than 100 times faster than any other optical quantum memory in existence.
The Team created the memory using caesium vapour as the medium for storage, the same stuff used in the world’s most precise atomic clocks. Quantum Memories are essential for the development of many devices in quantum information processing, including applications in timing quantum computers, extending secure quantum communications distances, new precision measurement clocks & spectroscopies, and single-photon light sources.
A glass cell is filled with hot caesium vapour. Two laser beams are used: one for writing and reading, and the other carrying the quantum bit signal to be stored. The ‘write’ pulse maps the incoming signal photons to an excitation spread over all of the caesium atoms, stopping it in its tracks. When the quantum bit is to be retrieved another ‘read’ laser maps the stored caesium excitation back into photons, which head off again at light-speed.
High-speed is the key feature which differentiates the new technique from its predecessors and the scheme developed is general enough for application to a variety of systems including gasses and solid materials. “There is a huge effort underway world-wide to develop quantum memories,” notes Dr. Sussman, “and the Team broke through the ceiling on quantum memory speeds - it’s blazing fast.”
Canada has gained a competitive advantage in this leading area of science through the success of this international collaboration. The next step will be to optimize the memory parameters by increasing the bandwidth even further and enhancing robustness. These objectives will take the memory from the research phase to the device stage, a goal that is well suited for the interdisciplinary teams at NRC.
Ottawa’s Photonics cluster which includes the Canadian Photonics Fabrication Centre is based on the strengths of Canada’s Information and Communication Technologies (ICT) Sector. NRC is poised to develop high-speed memories that will form the basis of fast, controllable and robust photonic quantum information processors in the near future. As a result, Canada will play a significant role in the development and fabrication of next-generation computing and communications technologies.
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