2025/11/15 by Abu-Nada, Ali, Iliat, Aryan, Ceballos, Russell
#FOS: Physical sciences #Quantum Physics (quant-ph)
paper · doi:10.48550/arxiv.2511.13774
Amplitude damping fundamentally limits qubit lifetimes by irreversibly leaking energy and information into the environment. Standard Wiseman--Milburn feedback offers only modest improvement because it acts on a single measured quadrature and its corrective drive is degraded by loop delay. We introduce a compact hybrid upgrade with two components: (i) a coherently coupled ancilla qubit that receives the homodyne current and feeds back quantum-coherently on the system, recovering information from both field quadratures and intentionally engineered to decay much faster than the system; and (ii) a lightweight supervised predictor that forecasts the near-future homodyne current, phase-aligning the correction to overcome hardware latency. A Lindblad treatment yields closed-form effective decay rates: the ancilla suppresses the emission channel by a cooperativity factor, while the predictor further suppresses the residual decay in proportion to forecast quality. Using IBM-scale parameters (baseline \(T1 = 50~μs\)), numerical simulations surpass the W--M limit, achieving \(∼ 3 - 4×\) longer \(T1\) together with improved population retention and integrated energy. The method is modular and hardware-compatible: ancilla coupling and supervised prediction can be added to existing W--M loops to convert leaked information into a precise, time-advanced corrective drive. We also include a detailed, student-friendly derivation of the effective rates for both ancilla-assisted and prediction-enhanced feedback, making the impact of each design element analytically transparent.