Artificial Coherent States of Light by Multiphoton Interference in a Single-Photon Stream

Area of Science:

• Quantum Optics
• Quantum Information Science

Background:

• Coherent optical states are quantum superpositions of photon number (Fock) states.
• Linear optics cannot extract Fock states from coherent states due to non-orthogonality.

Purpose of the Study:

• To demonstrate the reverse process: creating engineered quantum states from a single-photon stream.
• To achieve tunable photon statistics, including approximate weak coherent states.

Main Methods:

• Utilizing quantum interference in an optical Sagnac loop.
• Manipulating a continuous single-photon stream from a semiconductor quantum dot in an optical microcavity.

Main Results:

• Successfully created engineered quantum states of light with tunable photon statistics.
• Achieved photon statistics with g^{(2)}(0)→1, indicating quantum interference of at least 3 photons.
• Demonstrated the creation of complex light states beyond simple coherent states.

Conclusions:

• Quantum interference in a Sagnac loop can engineer complex quantum states of light.
• These engineered states exhibit photon entanglement, serving as a resource for multiphoton entanglement applications.