Noncommutative graphs based on finite-infinite system couplings: Quantum error correction for a qubit coupled to a coherent field

Abstract

Quantum error correction plays a key role for quantum information transmission and quantum computing. In this work, we develop and apply the theory of non-commutative operator graphs to study error correction in the case of a finite-dimensional quantum system coupled to an infinite dimensional system. We consider as an explicit example a qubit coupled via the Jaynes-Cummings Hamiltonian with a bosonic coherent field. We extend the theory of non-commutative graphs to this situation and construct, using the Gazeau-Klauder coherent states, the corresponding non-commutative graph. As the result, we find the quantum anticlique, which is the projector on the error correcting subspace, and analyze it as a function of the frequencies of the qubit and the bosonic field. The general treatment is also applied to the analysis of the error correcting subspace for certain experimental values of the parameters of the Jaynes-Cummings Hamiltonian. The proposed scheme can be applied to any system that possess the same decomposition of spectrum of the Hamiltonian into a direct sum as in JC model, where eigenenergies in the two direct summands form strictly increasing sequences.