Researchers have achieved a major breakthrough in quantum optics. They have created the first-ever quantum memory for X-ray photons. Quantum optics studies how light interacts with atoms and molecules at the quantum level. An international team, including Dr. Olga Kocharovskaya from Texas A&M University, led this impressive work. This achievement could lead to advanced quantum technologies that use X-ray energies.
Quantum Memory: How It Works
Quantum memory is key for quantum networks. It allows us to store and retrieve quantum information encoded in photons. Photons are great at carrying quantum information. But it’s hard to keep them still for future use. The team found a new way to solve this problem. They transfer the quantum information into a medium that doesn’t move much. This medium could be a polarization wave or a spin wave. These waves have long coherence times, meaning they keep their state for a long time. Later, the team can release the original photons by re-emitting them.
The Power of Nuclear Ensembles
The key to the team’s success is using nuclear ensembles instead of atomic ones. Nuclear ensembles provide much longer memory times. This works even at high solid-state densities and room temperature. The reason is that nuclear transitions are less sensitive to outside disturbances. This happens because nuclei are very small. The researchers also focus high-frequency photons very tightly. This approach has led them to develop a solid-state quantum memory system. This system is long-lived, broad-band, and compact.
Dr. Xiwen Zhang is a postdoctoral researcher in Kocharovskaya’s group. Dr. Zhang participated in the experiment. He says their new method for X-ray quantum memory is very different from the usual optical or atomic methods. They form a frequency comb in the absorption spectrum. This comb is created by moving nuclear absorbers. These absorbers shift the frequency due to Doppler effects. When a short pulse matches this comb’s spectrum, it is absorbed by the nuclear targets. It is then re-emitted after a delay. This delay is determined by the inverse Doppler shift. The re-emission happens due to constructive interference between the different spectral parts.
Conclusion
The team successfully implemented this protocol. They used one stationary and six moving absorbers to create a seven-teeth frequency comb. This was the first time quantum memory was realized in the hard X-ray range. The lifetime of nuclear coherence limits the maximum storage time. However, their work shows potential for extending optical quantum technologies to shorter wavelengths. Shorter wavelengths are naturally less affected by noise because they average out fluctuations over many high-frequency oscillations.
The researchers are now focusing on the next steps. These include the on-demand release of stored photon wave packets. They also aim to achieve entanglement between different hard X-ray photons. Entanglement is a crucial resource for quantum information processing. Dr. Kocharovskaya notes that their tunable, robust, and versatile platform has great potential. It can significantly advance the field of quantum optics at X-ray energies soon.
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