Pushing The Limit Of Quantum Memory

By cooling rubidium atoms to nearly absolute zero temperatures and increasing the signal-to-noise ratio of single photons, scientists in Hong Kong have found a way to improve the efficiency of quantum memory.

AsianScientist (May 13, 2019) – A team of scientists in Hong Kong has discovered a method to boost the efficiency of photonic quantum memories to over 85 percent with a fidelity of over 99 percent. They published their findings in Nature Photonics.

Like 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. Such quantum computers may push the boundaries of fundamental science and help create new drugs, explain cosmological mysteries or enhance accuracy of forecasts.

Quantum computers are expected to be much faster and more powerful than their traditional counterparts as information is calculated in quantum bits—or qubits—which can represent both 0 and 1 at the same time, unlike the bits of traditional computers. However, the production of highly efficient quantum memories remains a major challenge as it requires a perfectly matched photon-matter quantum interface.

In the present study, researchers led by Professors Du Shengwang and William Mong at the Hong Kong University of Science and Technology created a quantum memory device by trapping billions of rubidium atoms into a hair-like tiny space.

Those atoms are cooled down to a temperature of nearly absolute zero using lasers and magnetic fields. Essentially, the polarization states of single photons can be reliably stored in the cooled rubidium atoms and retrieved later, forming the basis of quantum memories.

“In this work, we code a flying qubit onto the polarization of a single photon and store it into the laser-cooled atoms,” said Du. “Although 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.”

The article can be found at: Wang et al. (2019) Efficient Quantum Memory for Single-photon Polarization Qubits.


Source: Hong Kong University of Science and Technology; Photo: Shutterstock.
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