Explicitly quantum-parallel computation by displacements

Area of Science:

• Quantum Information Science
• Quantum Optics
• Quantum Computing

Background:

• Quantum information encoding is susceptible to channel losses and environmental noise.
• Existing methods for creating quantum superpositions, like cat states, have limitations in fidelity.
• Non-Gaussian states are crucial for advanced quantum computation but challenging to generate and maintain.

Purpose of the Study:

• To introduce a novel encoding of information in optical modes for robust quantum parallel processing.
• To demonstrate the creation of high-fidelity quantum superpositions of squeezed states using photon subtraction.
• To explore the practical considerations for implementing an optical quantum annealer based on this encoding.

Main Methods:

• Encoding information in the relative displacement or photon number of optical modes.
• Utilizing photon subtraction protocols to generate quantum superpositions.
• Analyzing the impact of squeezing and non-Gaussian fluctuations on information encoding and loss.

Main Results:

• Developed an encoding scheme relatively protected from imperfections due to its insensitivity to squeezing and non-Gaussian fluctuations.
• Achieved significantly higher fidelity for quantum superpositions of squeezed states compared to cat states.
• Demonstrated that moderate squeezing and anti-squeezing are introduced, not dominating photon number.

Conclusions:

• The proposed encoding method offers a robust pathway for quantum parallel processing, leveraging non-Gaussian interference.
• Photon subtraction protocols are effective for generating high-quality quantum superpositions.
• Optical quantum annealers can be realized using differential photon number encoding with careful consideration of loss channels and error correction.