Decoherence of an $n$-qubit quantum memory

Gorin, Thomas; Pineda, Carlos; Seligman, Thomas H.

Decoherence of an $n$-qubit quantum memory

Authors

Gorin, Thomas

Pineda, Carlos

Seligman, Thomas H.

Description

We analyze decoherence of a quantum register in the absence of non-local operations i.e. of $n$ non-interacting 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 the coupling of different qubits must be uncorrelated in the interaction picture. We apply the result to a random matrix model, and illustrate its reach considering a GHZ state coupled to a spin bath.
4 pages, 2 figures