Atomic quantum memory enables synchronization of single photons

Quantum physics faces a significant challenge in efficiently synchronizing independently generated photons. This synchronization is crucial for quantum information processing that relies on interactions between multiple photons. Researchers at the Weizmann Institute of Science achieved a breakthrough by demonstrating the synchronization of single, independently generated photons using a room-temperature atomic quantum memory. Their work, published in Physical Review Letters, could revolutionize the study of multi-photon states and their application in quantum information processing.

The project idea took shape when the researchers, including Omri Davidson, explored atomic quantum memory with an inverted atomic-level scheme called fast ladder memory (FLAME). Unlike conventional memories, FLAME is fast and noise-free, making it suitable for synchronizing single photons. Photonic quantum computation and other quantum protocols require multi-photon states, but most existing quantum sources are probabilistic and unsuitable for generating them efficiently.

Davidson’s team rebuilt the memory with improvements and developed a single-photon source that efficiently interfaces with the memory. Their atomic quantum memory can store probabilistically generated photons and release them on-demand to create multi-photon states. FLAME, the quantum memory used, is fast and noise-free, making it ideal for single photon synchronization. This groundbreaking research has opened new possibilities for the field of quantum information processing.

Davidson and his team’s FLAME memory scheme offered several advantages for synchronizing individual photons. The small wavelength mismatch between signal and control light-fields transitions in rubidium atoms allowed for a relatively long memory lifetime, thanks to reduced two-photon Doppler broadening. Additionally, they generated photons using the same atomic-level structure as their memory, enabling efficient coupling of photons with the memory.

Their experiment achieved remarkable results, synchronizing photons at a high rate. With an end-to-end efficiency of 25% and a final antibunching measure of 0.023, the synchronized photons remained almost perfect single-photons, thanks to the noise-free operation of the memory.

The significance of their work lies in the ability to synchronize photons compatible with atomic systems at a high rate, which is crucial for photonic quantum information protocols like deterministic two-qubit entangling gates. The achieved photon synchronization rate was over 1,000 times better than previous demonstrations using photons compatible with atomic systems.

Davidson and his team are now exploring two research paths. First, they aim to achieve strong photon-photon interactions with rubidium atoms to demonstrate a deterministic entangling gate between synchronized single-photons, an essential component in photonic quantum computation. They also plan to enhance their FLAME memory to store photonic qubits, enabling quantum computations using photons.

The success of their experiments opens new avenues for studying multi-photon interactions with atoms, offering valuable implications for quantum information processing and quantum optics systems.

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