Quantum signaling in cavity QED
Robert H. Jonsson, Eduardo Martín-Martínez, Achim Kempf · Physical Review A · 2014
We consider quantum signaling between two-level quantum systems in a cavity in the perturbative regime of the earliest possible arrival times of the signal. We present two main results: First, we find that, perhaps surprisingly, the analog of amplitude modulated signaling (Alice using her energy eigenstates $\left|g\right\ensuremath{\rangle},\left|e\right\ensuremath{\rangle}$, as in the Fermi problem) is generally suboptimal for communication, namely, e.g., phase-modulated signaling (Alice using, e.g., ${\left|+\right\ensuremath{\rangle},\left|\ensuremath{-}\right\ensuremath{\rangle}}$ states) overcomes the quantum noise already at a lower order in perturbation theory. Second, we study the effect of mode truncations that are commonly used in cavity QED on the modeling of the communication between two-level atoms. We show that, on general grounds, namely for causality to be preserved, the UV cutoff must scale at least polynomially with the desired accuracy of the predictions.