Realization of fast fault-tolerant quantum gates on a single spin is the core requirement for solid-state quantum-information processing. As polarized light shows geometric interference, spin coherence is also geometrically controlled with light via the spin-orbit interaction. Here, we show that a geometric spin in a degenerate subspace of a spin-1 electronic system under a zero field in a nitrogen vacancy center in diamond allows implementation of optical non-adiabatic holonomic quantum gates. The geometric spin under quasi-resonant light exposure undergoes a cyclic evolution in the spin-orbit space, and acquires a geometric phase or holonomy that results in rotations about an arbitrary axis by any angle defined by the light polarization and detuning. This enables universal holonomic quantum gates with a single operation. We demonstrate a complete set of Pauli quantum gates using the geometric spin preparation and readout techniques. The new scheme opens a path to holonomic quantum computers and repeaters.3 Main textA quantum bit or qubit must be capable of being precisely and quickly manipulated, as well as robust against noise. These criteria pose a dilemma in that the qubit must be open for a driving field but not for a noise field. It has been demonstrated that the degenerate subspace of a spin-1 electronic system under a zero field, which we call a geometric spin, can serve as a promising memory qubit that is robust against environmental noise 1 . The challenge is to manipulate the degenerate qubit with the help of a geometric phase. The concept of the geometric phase was first proposed by Pancharatnam in 1956 2 in reference to light polarization. Since then, two kinds of geometric phase have been discussed. Adiabatic geometric phases were first proposed by Berry in 1984 3 , and nonadiabatic non-Abelian geometric phases were proposed by Anandan in 1988 4 . Holonomic quantum computation (HQC) based on the adiabatic geometric phase was then proposed for fault-tolerant quantum gates by Zanardi and Rasetti in 1999 5 , and generalized to non-adiabatic HQC by Wang and Matsumoto in 2001 6,7 and Zhu and Wang in 2002 8 . The geometric phase has been experimentally demonstrated in molecular ensembles 8,9 , in a superconducting qubit 10 , in trapped ions 11,12 , in a quantum dot 13,14 , and in a single nitrogen-vacancy (NV) center in diamond 15-17 .

We demonstrate universal non-adiabatic non-abelian holonomic single quantum gates over a geometric electron spin with phase-modulated polarized light and 93% average fidelity. This allows purely geometric rotation around an arbitrary axis by any angle defined by light polarization and phase using a degenerate three-level Λ-type system in a negatively charged nitrogen-vacancy center in diamond. Since the control light is completely resonant to the ancillary excited state, the demonstrated holonomic gate not only is fast with low power, but also is precise without the dynamical phase being subject to control error and environmental noise. It thus allows pulse shaping for further fidelity.

Quantum teleportation is a key principle for quantum information technology. It permits the transfer of quantum information into an otherwise inaccessible space, while also permitting the transfer of photon information into a quantum memory without revealing or destroying the stored quantum information. Here, we show reliable quantum state transfer of photon polarization into a carbon isotope nuclear spin coupled to a nitrogen-vacancy center in diamond based on photon-electron Bell state measurement by photon absorption. The carbon spin is first entangled with the electron spin, which is then permitted to absorb a photon into a spin-orbit correlated eigenstate. Detection of the electron after relaxation into the spin ground state allows post-selected transfer of arbitrary photon polarization into the carbon memory. The quantum state transfer scheme allows individual addressing of integrated quantum memories to realize scalable quantum repeaters for long-haul quantum communications, and distributed quantum computers for large-scale quantum computation and metrology.

No abstract

The authors verified an energy saving effect of an air lubrication system for the domestic service ferry which was one of slender body ships. The energy saving effect was evaluated by the engine output reduction rate of system ON and OFF at speed-trial test. As the result, a net energy saving effect of about 3.7% was confirmed. After that, long-term voyage monitoring had been conducted since the ship was in service. At the same time, monitoring had been conducted about same type of sister ship without air lubrication system, in service on the same route. The investigation result of the energy saving effect by comparison of fuel consumption of both ships, a net effect of about 3.13% was confirmed. According to these results, the effectiveness of an air lubrication system for slender body ships was proved; therefore, scope of an air lubrication system as energy saving system of ships had expanded.