Analytical fidelity calculations for photonic linear cluster state generation

Area of Science:

• Quantum Information Science
• Quantum Computing
• Optics and Photonics

Background:

• Optical emitters like quantum dots can generate linear photonic cluster states.
• These states are crucial for reducing resource overhead in fault-tolerant optical quantum computing.
• Existing methods face limitations due to spin decoherence and finite excited state lifetimes.

Purpose of the Study:

• To develop an analytical algorithm for tracking the global density matrix during linear cluster state generation.
• To derive a model for calculating entangling gate and state fidelity for generated linear optical cluster states.
• To investigate the impact of error sources and identify optimal device parameters.

Main Methods:

• Analytical tracking of the global density matrix.
• Development of a fidelity calculation model incorporating spin decoherence and excited state lifetime.
• Analysis of partial spin coherence reinitialization upon photon emission.

Main Results:

• A model was derived to calculate entangling gate and state fidelity.
• Partial reinitialization of spin coherence was identified, mitigating coherence time limitations.
• Near-unity fidelities were achieved for 3-photon and 7-photon cluster states with state-of-the-art quantum dots.

Conclusions:

• The developed framework provides insights into cost-to-improvement trade-offs for device design.
• Optimal working points for quantum dot parameters were identified.
• The method enables high-fidelity generation of linear photonic cluster states essential for quantum computing.