Lost, but not Forgotten: Extracting Quantum Information in Noisy Systems

This talk explores the concept of noisy quantum trees, examining how quantum information can be preserved despite noise interference. Learn how at each tree node, received qubits interact unitarily with fresh ancilla qubits before being transmitted through noisy channels to the next level. Discover how novel decoders demonstrate that quantum information can be indefinitely preserved in infinite noisy quantum trees without requiring mid-circuit error correction. The presentation also establishes thresholds above which quantum information decays exponentially with tree depth. The latter portion addresses optimal distillation of pure coherent states from coherent thermal states in bosonic systems using time-translation invariant operations, revealing that the lowest achievable error is proportional to the inverse of the input state's purity of coherence—a finding that provides an operational interpretation of the Right-Logarithmic-Derivative Fisher information metric.