分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: 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 a fundamental 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 prepare strategy. This device features high reliability, easy scalability and can be directly integrated into fiber networks, which could play an essential role in fiber-based quantum networks.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Quantum memory is a fundamental building block for large-scale quantum networks. On-demand optical storage with a large bandwidth, a high multimode capacity and an integrated structure simultaneously is crucial for practical application. However, this has not been demonstrated yet. Here, we fabricate an on-chip waveguide in a $\mathrm {^{151}Eu^{3+}:Y_2SiO_5}$ crystal with insertion losses of 0.2 dB, and propose a novel pumping scheme to enable spin-wave atomic frequency comb (AFC) storage with a bandwidth of 11 MHz inside the waveguide. Based on this, we demonstrate the storage of 200 temporal modes using the AFC scheme and conditional on-demand storage of 100 temporal modes using the spin-wave AFC scheme. The interference visibility between the readout light field and the reference light field is $99.0\% \pm 0.6\%$ and $97\% \pm 3\%$ for AFC and spin-wave AFC storage, respectively, indicating the coherent nature of this low-loss, multimode and integrated storage device.
分类: 光学 >> 量子光学 提交时间: 2023-02-19
摘要: Optically addressable spins in two-dimensional hexagonal boron nitride (hBN) attract widespread attention for their potential advantage in on-chip quantum devices, such as quantum sensors and quantum network. A variety of spin defects have been found in hBN, but no convenient and deterministic generation methods have been reported for other defects except negatively charged boron vacancy ($\rm V_B^-$). Here we report that by using femtosecond laser direct writing technology, we can deterministically create spin defect ensembles with spectra range from 550 nm to 800 nm. Positive single-peak optically detected magnetic resonance (ODMR) signals are detected in the presence of longitudinal magnetic field, and the contrast can reach 0.8%. With the appropriate thickness of hBN flakes and femtosecond laser pulse energy, we can deterministically generate bright spin defects in-situ. Our results provide a convenient deterministic method to create spin defects in hBN, which will motivate more endeavors for future researches and applications of spin-based technologies.