Retrieving qubit information despite decoherence

Decoherence effects on quantum Fisher information of multi-qubit W states

Quantum fisher information of a parameter characterizing the sensitivity of a state with respect to parameter changes. In this paper, we study the quantum fisher information of the W state for four, five, six and seven particles in decoherence channels, such as amplitude damping, phase damping and depolarizing channel. Using Krauss operators for decoherence channels components, we investigate t...

Low-decoherence flux qubit

J. Q. You,1,2 Xuedong Hu,3 S. Ashhab,2 and Franco Nori2,4 1Department of Physics and Surface Physics Laboratory (National Key Laboratory), Fudan University, Shanghai 200433, China 2Frontier Research System, The Institute of Physical and Chemical Research (RIKEN), Wako-shi 351-0198, Japan 3Department of Physics, University at Buffalo, SUNY, Buffalo, New York 14260-1500, USA 4Center for Theoretic...

Optimal dynamical decoherence control of a qubit.

We present a theory of dynamical control by modulation for optimal decoherence reduction. The theory is based on the non-Markovian Euler-Lagrange equation for the energy-constrained field that minimizes the average dephasing rate of a qubit for any given dephasing spectrum.

One , Two , and n Qubit Decoherence

Decoherence of an n-qubit quantum memory.

We analyze decoherence of a quantum register in the absence of nonlocal operations, i.e., n noninteracting qubits coupled to an environment. The problem is solved in terms of a sum rule which implies linear scaling in the number of qubits. Each term involves a single qubit and its entanglement with the remaining ones. Two conditions are essential: first, decoherence must be small, and second, t...