Similar to memories in computers, quantum memories are essential components for quantum computers, a new generation of data processors that obey quantum mechanics laws and can overcome the limitations of classical computers.
It may seem possible for them to push boundaries of fundamental science and aid with the creation of new drugs, explain cosmological mysteries, or enhance the accuracy of forecasts and optimization plans with their reliable computational power. The expectation of quantum computer is for them to be much faster and more powerful than their traditional counterparts as information is calculated in qubits, which unlike the older units, bits, used in classical computers, can represent both zero and one at the same time.
Part of qualities of photonic quantum memories is the allowance for the storage and retrieval of flying single-photon quantum states. To produce such highly-efficient quantum memories, however, remains a significant challenge as it requires a perfectly matched photon-matter interface. Meanwhile, the energy of a single photon is too weak and can be easily lost into the noisy sea of stray light background. For so long, these problems suppressed quantum memory efficiencies to below 50 percent, a threshold value crucial for practical applications.
Recently, and for the first time in history, some researchers joined forced and discovered a way to boost the efficiency of photonic quantum memories to over 85 percent with the fidelity of over 99 percent. The new study was published as a cover story of the authoritative journal Nature Photonics. The team comprised of Prof. DU Shengwang, who was the team leader, is from the Department of Physics and William Mong Institute of Nano Science and Technology at HKUST, Prof. ZHANG Shanchao from SCNU who graduated his Ph.D., study at HKUST, Prof. YAN Hui from SCNU and a former postdoctoral fellow at HKUST, as well as Prof. ZHU Shi-Liang fromSCNU and Nanjing University.
The scientists created such a quantum memory by trapping billions of rubidium atoms into a hair like tiny space; those atoms are cooled down to nearly absolute zero temperature, about 0.00001 K, using lasers and magnetic field. The team also found a smart way to distinguish the single photon from the noisy background light sea. The discovery brought the dream of a 'universal' quantum computer a step closer to reality. They can also use such quantum memories as repeaters in a quantum network, laying the foundation for a new generation of quantum-based internet.
Prof. Du said that they code a flying qubit in this work onto the polarization of a single photon and store it into the laser-cooled atoms. Even when the quantum memory demonstrated in this work is only for one qubit operation, it opens the possibility for emerging quantum technology and engineering in the future.
