Dür W, Sekatski P, Skotiniotis M
Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
Phys Rev Lett. 2015 Mar 27;114(12):120503. doi: 10.1103/PhysRevLett.114.120503. Epub 2015 Mar 25.
We show that one can deterministically generate, out of N copies of an unknown unitary operation, up to N^{2} almost perfect copies. The result holds for all operations generated by a Hamiltonian with an unknown interaction strength. This generalizes a similar result in the context of phase-covariant cloning where, however, superreplication comes at the price of an exponentially reduced probability of success. We also show that multiple copies of unitary operations can be emulated by operations acting on a much smaller space, e.g., a magnetic field acting on a single n-level system allows one to emulate the action of the field on n^{2} qubits.
我们证明，从N个未知酉操作的副本中，可以确定性地生成多达N²个几乎完美的副本。该结果适用于由具有未知相互作用强度的哈密顿量生成的所有操作。这推广了相位协变克隆背景下的一个类似结果，然而，超复制是以成功概率指数降低为代价的。我们还表明，酉操作的多个副本可以通过作用在小得多的空间上的操作来模拟，例如，作用在单个n能级系统上的磁场允许模拟该场对n²个量子比特的作用。
