Unlocking the Potential of Non-Fock States: A Leap Forward in Optical Quantum Technologies

Japanese Researchers Discover the Stability and Advantages of Non-Fock States in Quantum Technology

Quantum technology holds immense promise for revolutionizing various fields, from computing to sensing. In the pursuit of advancements in optical quantum computing and sensing, a team of Japanese researchers has made a groundbreaking discovery regarding non-Fock states (iNFS). These complex quantum states, requiring more than a single photon source and linear optical elements, exhibit unique stability and properties that could unlock new possibilities in the field. This breakthrough has significant implications for optical quantum technologies, paving the way for advancements in optical quantum computers, quantum cryptography, and quantum sensing.

Unveiling the Advantages of Non-Fock States:

The team of researchers from Kyoto University and Hiroshima University has successfully confirmed the existence of iNFS through theoretical and experimental studies. By utilizing an optical quantum circuit with multiple photons, they demonstrated the unique advantages of non-Fock states. Unlike Fock states, which rely on combining one-photon inputs, iNFS require more complex processes and multiple photons. This discovery opens up new avenues for harnessing the potential of photonic quantum technologies.

The Promise of Optical Quantum Technologies:

Photon-based systems offer great potential for quantum technology due to their ability to preserve quantum states over long distances at room temperature. By harnessing many photons in multiple modes, optical quantum technologies can enable long-distance optical quantum cryptography, optical quantum sensing, and optical quantum computing. The stability and properties of non-Fock states provide a promising avenue for advancing these applications.

Overcoming Challenges in Generating Complex iNFS:

Generating complex non-Fock states is a challenging task that the researchers tackled with great dedication. They utilized a Fourier transform photonic quantum circuit to manifest two photons in three different pathways, a phenomenon known as conditional coherence. This intricate process represents a significant milestone in the generation of iNFS and highlights the potential for further advancements in optical quantum technologies.

Comparing Non-Fock States to Quantum Entanglement:

In their study, the researchers compared non-Fock states to the widely studied phenomenon of quantum entanglement. While quantum entanglement appears and disappears with the traversal of a single linear optical element, non-Fock states exhibit remarkable stability even when passing through a network of multiple linear optical elements. This comparison highlights the unique properties and potential of non-Fock states in optical quantum technology.

Future Directions and Implications:

The discovery of the stability and advantages of non-Fock states opens up exciting possibilities for the future of quantum technology. The research team aims to realize larger-scale multiphoton, multimode states, and optical quantum circuit chips in their next phase. This advancement could lead to significant breakthroughs in optical quantum computers, quantum sensing devices, and quantum cryptography systems.


The recent discovery of the stability and properties of non-Fock states by Japanese researchers represents a significant leap forward in the field of optical quantum technologies. The ability to harness the unique advantages of non-Fock states opens up new possibilities for advancements in optical quantum computing, quantum sensing, and quantum cryptography. As researchers continue to explore and develop these complex quantum states, the potential for transformative applications in various fields becomes increasingly promising. The future of quantum technology is on the horizon, and non-Fock states play a crucial role in unlocking its vast potential.

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