Charge Qubit Purification by an Electronic Feedback Loop

Reconsidering Rapid Qubit Purification by Feedback

This paper reconsiders the properties of a scheme for the rapid purification of the quantum state of a qubit, proposed recently in Jacobs 2003 Phys. Rev. A 67 030301(R). The qubit starts in a completely mixed state, and information is obtained by a continuous measurement. Jacobs’ rapid purification protocol uses Hamiltonian feedback control to maximise the average purity of the qubit for a give...

Optimality of Feedback Control Strategies for Qubit Purification

Purification of Logic-Qubit Entanglement

Recently, the logic-qubit entanglement shows its potential application in future quantum communication and quantum network. However, the entanglement will suffer from the noise and decoherence. In this paper, we will investigate the first entanglement purification protocol for logic-qubit entanglement. We show that both the bit-flip error and phase-flip error in logic-qubit entanglement can be ...

Robust charge-based qubit encoding

Quantum computation faces considerable hurdles, one of the most serious being engineering physical systems performing coherent operations without the deleterious effects of decoherence,1 particularly in the solid state. However by isolation and manipulation of states of quantum dot QD structures,2 it may be possible to perform many unitary operations within the dephasing time, a pre-requisite f...

Global versus local optimality in feedback-controlled qubit purification: new insights from minimizing Rényi entropies

It was first shown by Jacobs, in 2003, that the process of qubit state purification by continuous measurement of one observable can be enhanced, on average, by unitary feedback control. Here, we quantify this by the reduction in any one of the family of Rényi entropies α S , with α < < ∞ 0 , at some terminal time, revealing the rich structure of stochastic quantum control even for this simple p...