On-Demand Storage of Photonic Qubits at Telecom Wavelengths.

Quantum memories at telecom wavelengths are crucial for the construction of large-scale quantum networks based on existing fiber networks. On-demand storage of telecom photonic qubits is an essential request for such networking applications but yet to be demonstrated. Here we demonstrate the storage and on-demand retrieval of telecom photonic qubits using a laser-written waveguide fabricated in an ^{167}Er^{3+}:Y_{2}SiO_{5} crystal. Both ends of the waveguide memory are directly connected with fiber arrays with a fiber-to-fiber efficiency of 51%. Storage fidelity of 98.3(1)% can be obtained for time-bin qubits encoded with single-photon-level coherent pulses, which is far beyond the maximal fidelity that can be achieved with a classical measure and prepared strategy. This device features high reliability and easy scalability, and it can be directly integrated into fiber networks, which could play an essential role in fiber-based quantum networks.

Research on three dimensional machining effects using atomic force microscope.

This research studies the use of scanning probe microscope as the tool to manufacture three dimensional nanoscale objects. We modified a commercial atomic force microscope (AFM) and replaced the original probe control system with a personal computer (PC) based controller. The modified system used the scanning probe in the AFM for the cutting tool and used the PC controller to control work piece. With the new controller, one could implement multiaxes motion control to perform trajectory planning and to test various cutting strategies. The experiments discovered that the debris can coalesce with the sample material and cause tremendous problem in the nanomachining process. This research thus proposed to make use of this material and developed a piling algorithm to not only cut but also pile up the debris in a favorable way for steric shaping. The experimental results showed that the proposed cutting and shaping algorithm can produce nano-objects as high as a few hundred nanometers. The probe tip typically wears down to around 500 microm diameter after the machining process, putting a limit on the machining resolution. The vertical resolution can achieve less than 10 nm without controlled environment.