Recovery With Incomplete Knowledge: Fundamental Bounds on Real-Time Quantum Memories

Understand

The recovery of fragile quantum states from decoherence is the basis of building a quantum memory, with applications ranging from quantum communications to quantum computing.

• Many recovery techniques, such as quantum error correction, rely on the apriori knowledge of the environment noise parameters to achieve their best performance.
• However, such parameters are likely to drift in time in the context of implementing long-time quantum memories.
• This necessitates using a "spectator" system, which estimates the noise parameter in real-time, then feed-forwards the outcome to the recovery protocol as a classical side-information.