title: Memory-built-in quantum cloning in a hybrid solid-state spin register.
abstract: As a way to circumvent the quantum no-cloning theorem, approximate quantum cloning protocols have received wide attention with remarkable applications. Copying of quantum states to memory qubits provides an important strategy for eavesdropping in quantum cryptography. We report an experiment that realizes cloning of quantum states from an electron spin to a nuclear spin in a hybrid solid-state spin register with near-optimal fidelity. The nuclear spin provides an ideal memory qubit at room temperature, which stores the cloned quantum states for a millisecond under ambient conditions, exceeding the lifetime of the original quantum state carried by the electron spin by orders of magnitude. The realization of a cloning machine with built-in quantum memory provides a key step for application of quantum cloning in quantum information science.
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, PR China.
authors.forename: W-B
authors.initials: WB
authors.lastname: Wang
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, PR China.
authors.forename: C
authors.initials: C
authors.lastname: Zu
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, PR China.
authors.forename: L
authors.initials: L
authors.lastname: He
authors.affiliation: Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, PR China.
authors.forename: W-G
authors.initials: WG
authors.lastname: Zhang
authors.affiliation: 1] Center for Quantum Information, IIIS, Tsinghua University, Beijing 100084, PR China [2] Department of Physics, University of Michigan, Ann Arbor, Michigan 48109, USA.
authors.forename: L-M
authors.initials: LM
authors.lastname: Duan