Masaki Owari, Koji Maruyama, Takeji Takui, Go Kato
The full control of many-body quantum systems is expected to be a key towards the future nano- and quantum technologies. Among others, the realisation of quantum information processing has been studied intensively as a good test bed of quantum control as well as an ultimate engineering task that makes full use of quantum mechanical effects. Yet, manipulating quantum states is extremely hard, since information encoded in quantum states easily leaks out to the environment due to the inevitable interactions with it. In the theory of open quantum systems, an environment is usually treated as a large bath, assuming that most of its dynamical details are averaged out. Thus we do not see it as a quantum object that we can control actively. In realistic situations, it is indeed near-impossible to precisely identify the quantum nature of an environment, let alone to control it at will. However, here we demonstrate how this formidable task can be achieved, provided the dimension of the environment can be regarded as finite within the timescale we manipulate the system. The information thereby obtained will be useful not only for deeper understanding of the system dynamics under decoherence but also for exploiting the environment as a resouce for quantum engineering, such as quantum computation.
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http://arxiv.org/abs/1301.2152
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