title: Deterministic superreplication of one-parameter unitary transformations.
abstract: 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.
authors: Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors: W
authors: W
authors: Dür
authors: Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors: P
authors: P
authors: Sekatski
authors: Institut für Theoretische Physik, Universität Innsbruck, Technikerstrasse 25, A-6020 Innsbruck, Austria.
authors: M
authors: M
authors: Skotiniotis