AGAINST QUANTUM-NOISE

This is a brief description of how to protect quantum states from diss ipation and decoherence that arise due to uncontrolled interactions wi th the environment. We discuss recoherence and stabilization of quantu m states based on two techniques known as ''symmetrization'' and ''qua ntum error correction''. We illustrate our considerations with the mos t popular quantum-optical model of the system-environment interaction, commonly used to describe spontaneous emission, and show the benefits of quantum error correction in this case.