Scalable symmetry detector and its applications by using beam splitters and weak nonlinearities

Area of Science:

• Quantum Optics
• Quantum Information Science
• Entanglement Studies

Background:

• Multiphoton entanglement is crucial for quantum technologies.
• Detecting and generating multi-pair entangled states remains challenging.
• Spontaneous parametric down-conversion (SPDC) is a common source for entangled photons.

Purpose of the Study:

• To introduce a novel method for detecting twin-beam multiphoton entanglement.
• To explore the generation and detection of two-pair entangled states using a symmetry detector.
• To generalize the detector for n-pair emissions and determine photon pair numbers from SPDC sources.

Main Methods:

• Utilized a beam splitter and weak nonlinearities for entanglement detection.
• Developed and applied a symmetry detector for twin-beam four-photon entanglement.
• Employed iterative calculations of coefficients and success probabilities for state generation.

Main Results:

• The symmetry detector efficiently collects two-pair entangled states directly from SPDC.
• Cascading symmetry detectors allows for the generation of two-pair entangled states.
• Achieved desired two-pair states from four-photon entangled states within a few iterations.
• Generalized the detector to determine the number of indistinguishable pairs emitted from SPDC.

Conclusions:

• The proposed symmetry detector is effective for detecting and generating multiphoton entanglement.
• This method offers a pathway to efficiently produce multi-pair entangled states.
• The generalization to n-pair emissions advances the exploration of large-scale multiphoton entanglement.