Optimality of feedback control for qubit purification under inefficient measurement
arXiv:1910.02487 · doi:10.1103/PhysRevA.102.022612
Abstract
A quantum system may be purified, i.e., projected into a pure state, faster if one applies feedback operations during the measurement process. However existing results suggest that such an enhancement is only possible when the measurement efficiency exceeds 0.5, which is difficult to achieve experimentally. We address the task of finding the global optimal feedback control for purifying a single qubit in the presence of measurement inefficiency. We use the Bloch vector length, a more physical and practical quantity than purity, to assess the quality of the state, and employ a backward iteration algorithm to find the globally optimal strategy. Our results show that a speedup is available for quantum efficiencies well below 0.5, which opens the possibility of experimental implementation in existing systems.
arXiv comment9 pages, 5 figures
References in corpus (11)
- Quantum trajectory approach to circuit QED: Quantum jumps and the Zeno effect
- Deterministic Dicke state preparation with continuous measurement and control
- Dynamics of simultaneously measured non-commuting observables
- How to project qubits faster using quantum feedback
- Reconsidering Rapid Qubit Purification by Feedback
- Rapid Measurement of Quantum Systems using Feedback Control
- Deterministic generation of remote entanglement with active quantum feedback
- Quantum Feedback Control: How to use Verification Theorems and Viscosity Solutions to Find Optimal Protocols
- Quantum feedback for rapid state preparation in the presence of control imperfections
- Maximum information gain in weak or continuous measurements of qudits: complementarity is not enough
- Optimality of qubit purification protocols in the presence of imperfections
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