Can quantum optics be used for practical applications? A lot depends on whether a large number of photons can be gathered in quantum state.
Among all quantum systems, photons are known for their weak interaction, which allows long coherence time to be achieved even at room temperature, making them suitable for transmitting quantum bits (also known as "qubits") between distant locations. However, the weak interaction of photons restricts the generation of quantum states known as multiphotonic qubit states, or "N-photon states." Generating N-photon states remains a fundamental challenge in the field of quantum optics.
As reported in Advanced Photonics Nexus, researchers from Nanjing University have proposed the first scheme that, in principle, can practically generate an N-photon state deterministically—so that photon number doubling happens with 100 percent efficiency—with unlimited numbers of photons. The scheme is experimentally feasible, taking account of practical material capability by using a lithium-niobate-on-insulator (LNOI) platform, which provides an ultrastrong χ(2) nonlinear interaction.
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