5-bit all-optical quantum random number generator based on a time-multiplexed optical parametric oscillator.

Area of Science:

• Quantum optics
• Information security

Background:

• Random numbers are crucial for secure communication, quantum computing, and cryptography.
• Degenerate optical parametric oscillators (DOPOs) offer a path to true randomness due to quantum process non-determinism.
• A key challenge for DOPOs in random number generation is scaling the bit sequence length.

Purpose of the Study:

• To experimentally generate 5-bit random number streams using a time-multiplexed femtosecond DOPO system.
• To address the challenge of bit sequence scalability in DOPO-based random number generation.
• To develop an all-optical random number generator with enhanced scalability.

Main Methods:

• Implementation of a time-multiplexed femtosecond degenerate optical parametric oscillator (DOPO).
• Integration of a multi-pass cell to elongate the optical parametric oscillator (OPO) cavity to approximately 15 meters.
• Resonance of 5 signal pulses at a 50 MHz repetition rate within the elongated cavity.
• Characterization of the output phase state via interference with fundamental pump pulses.
• Verification of randomness using conditional probability analysis on 1200 bits.

Main Results:

• Successful generation of 5-bit random number streams from the femtosecond DOPO system.
• Demonstration of an elongated OPO cavity (∼15 m) capable of resonating 5 signal pulses at 50 MHz.
• Confirmation that above-threshold binary phase originates from vacuum fluctuations, ensuring system randomness.
• Experimental verification of the randomness of the generated bit sequences.

Conclusions:

• The developed scheme successfully generates 5-bit random number streams with enhanced scalability.
• The use of an elongated OPO cavity with a multi-pass cell is effective for increasing bit sequence length.
• This work presents a promising direction for the development of scalable all-optical random number generators.