QUROPE Quantum Information Processing and Communication in Europe

Quantum teleportation from a telecom-wavelength photon to a solid-state quantum memory
F. Bussières, C. Clausen, A. Tiranov, B. Korzh, V. B Verma, S.W. Nam, F. Marsili, A. Ferrier, P. Goldner, H. Herrmann, C. Silberhorn, W. Sohler, M. Afzelius, N. Gisin
Nature Photonics 8, 775-778 (2014);
Unconditional quantum teleportation between distant solid-state quantum bits
W. Pfaff, B.J. Hensen, H. Bernien, S.B. van Dam, M.S. Blok, T.H. Taminiau, M.J. Tiggelman, R.N. Schouten, M. Markham, D.J. Twitchen, R. Hanson
Science 345, 532-535 (2014)

Quantum teleportation allows for the transfer of arbitrary, in principle, unknown quantum states from a sender to a spatially distant receiver, who share an entangled state and can communicate classically. It is essential for long-distance transmission of quantum information using quantum repeaters. This requires the efficient distribution of entanglement between remote nodes of a network. These two works report two significant experimental demonstrations of quantum teleportation, in solid-state quantum memories and between defects in diamond.

In the first work, Bussières and co-workers demonstrate quantum teleportation of the polarization state of a telecom-wavelength photon onto the state of a solid-state quantum memory. Entanglement is established between a rare-earth-ion-doped crystal storing a single photon that is polarization-entangled with a flying telecom-wavelength photon. The latter is jointly measured with another flying polarization qubit to be teleported, which heralds the teleportation. The fidelity of the qubit retrieved from the memory is shown to be greater than the maximum fidelity achievable without entanglement, even when the combined distances travelled by the two flying qubits is 25 km of standard optical fibre. These results demonstrate the possibility of long-distance quantum networks with solid-state resources.

In the second work, Pfaff and co-workers demonstrate unconditional teleportation of arbitrary quantum states between diamond spin qubits separated by 3 meters. The teleporter is prepared through photon-mediated heralded entanglement between two distant electron spins. The source qubit is encoded in a single nuclear spin. By realizing a fully deterministic Bell-state measurement combined with real-time feed-forward, quantum teleportation is achieved upon each attempt with an average state fidelity exceeding the classical limit. These results establish diamond spin qubits as a prime candidate for the realization of quantum networks for quantum communication and network-based quantum computing.