Measurement-angle control of a continuously monitored quantum oscillator: purification limits and optimal protocols

arXiv:2611.00410v1 Announce Type: new Abstract: We study the dynamic purification of a continuously monitored quantum harmonic oscillator coupled to a thermal bath, where the control is the quadrature measurement angle of up to two detectors with prescribed strengths and efficiencies. Within the Gaussian regime, the conditional state covariance obeys a deterministic Riccati equation, and we ask what purity can be reached and sustained by manipulating the angle in time, in analogy with rapid-purification protocols for qubits.