Introduction

Efficiently generating entangled single photon states is the starting point for a number of applications in quantum information, quantum computation and secure communications. The present invention gives the right solution in this direction through a photon source and an entanglement generation stage between two selected states of a single photon. It consists of an apparatus that can be formed by discrete components or can be fully or partly realized with an integrated optical circuit.

Technical features

The proposed invention aims at generating quantum correlations (entanglement) between two states of the same photon. The key aspect of the invention is the manipulation of different degrees of freedom of a single photon. These can be the polarization, the momentum, the angular momentum, the mode of propagation, or the frequency. The invention demonstrates how to prepare single photon entangled states with photons emitted by any coherent or incoherent light source. A necessary condition is to maintain coherence between the used degrees of freedom and to use a photon flux within the dynamic range of the measurement system. The apparatus developed in the invention manages to generate quantum correlations by providing limited costs and requiring low power, lower energy consumption, lower heat dissipation than existing devices, and moreover is also light, compact, and can be miniaturized.

Possible Applications

• Quantum information;
• Quantum computer;
• Secure communication;
• Certified quantum random number generation;
• Quantum key distribution;
• Cryptography;
• Quantum measurements and quantum sensing;
• Internet of Things.

Advantages

• Avoid the use of power laser;
• Robust with respect to ambient and decoherence;
• Low power consumption;
• Compact and light;
• Small size;
• Cheap;
• Photons from the different spectral range;
• Easy to integrate into optical chips.